dynamic linker bootstrap overhaul

this overhaul further reduces the amount of arch-specific code needed
by the dynamic linker and removes a number of assumptions, including:

- that symbolic function references inside libc are bound at link time
  via the linker option -Bsymbolic-functions.

- that libc functions used by the dynamic linker do not require
  access to data symbols.

- that static/internal function calls and data accesses can be made
  without performing any relocations, or that arch-specific startup
  code handled any such relocations needed.

removing these assumptions paves the way for allowing libc.so itself
to be built with stack protector (among other things), and is achieved
by a three-stage bootstrap process:

1. relative relocations are processed with a flat function.
2. symbolic relocations are processed with no external calls/data.
3. main program and dependency libs are processed with a
   fully-functional libc/ldso.

reduction in arch-specific code is achived through the following:

- crt_arch.h, used for generating crt1.o, now provides the entry point
  for the dynamic linker too.

- asm is no longer responsible for skipping the beginning of argv[]
  when ldso is invoked as a command.

- the functionality previously provided by __reloc_self for heavily
  GOT-dependent RISC archs is now the arch-agnostic stage-1.

- arch-specific relocation type codes are mapped directly as macros
  rather than via an inline translation function/switch statement.

Makefile

@@ -85,7 +85,7 @@ src/internal/version.h: $(wildcard VERSION .git)
 
 src/internal/version.lo: src/internal/version.h
 
-src/ldso/dynlink.lo: arch/$(ARCH)/reloc.h
+src/ldso/dlstart.lo src/ldso/dynlink.lo: src/internal/dynlink.h arch/$(ARCH)/reloc.h
 
 crt/crt1.o crt/Scrt1.o: $(wildcard arch/$(ARCH)/crt_arch.h)
 

arch/aarch64/crt_arch.h

@@ -1,9 +1,14 @@
 __asm__(
-".global _start\n"
-".type _start,%function\n"
-"_start:\n"
+".global " START "\n"
+".type " START ",%function\n"
+START ":\n"
 "	mov x29, #0\n"
 "	mov x30, #0\n"
 "	mov x0, sp\n"
+".weak _DYNAMIC\n"
+".hidden _DYNAMIC\n"
+"	adrp x1, _DYNAMIC\n"
+"	add x1, x1, #:lo12:_DYNAMIC\n"
 "	and sp, x0, #-16\n"
-"	b __cstart\n");
+"	b " START "_c\n"
+);

arch/aarch64/reloc.h

@@ -1,5 +1,3 @@
-#include <string.h>
-#include <elf.h>
 #include <endian.h>
 
 #if __BYTE_ORDER == __BIG_ENDIAN
@@ -14,27 +12,15 @@
 
 #define TPOFF_K 16
 
-static int remap_rel(int type)
-{
-	switch(type) {
-	case R_AARCH64_ABS64:
-		return REL_SYMBOLIC;
-	case R_AARCH64_GLOB_DAT:
-		return REL_GOT;
-	case R_AARCH64_JUMP_SLOT:
-		return REL_PLT;
-	case R_AARCH64_RELATIVE:
-		return REL_RELATIVE;
-	case R_AARCH64_COPY:
-		return REL_COPY;
-	case R_AARCH64_TLS_DTPMOD64:
-		return REL_DTPMOD;
-	case R_AARCH64_TLS_DTPREL64:
-		return REL_DTPOFF;
-	case R_AARCH64_TLS_TPREL64:
-		return REL_TPOFF;
-	case R_AARCH64_TLSDESC:
-		return REL_TLSDESC;
-	}
-	return 0;
-}
+#define REL_SYMBOLIC    R_AARCH64_ABS64
+#define REL_GOT         R_AARCH64_GLOB_DAT
+#define REL_PLT         R_AARCH64_JUMP_SLOT
+#define REL_RELATIVE    R_AARCH64_RELATIVE
+#define REL_COPY        R_AARCH64_COPY
+#define REL_DTPMOD      R_AARCH64_TLS_DTPMOD64
+#define REL_DTPOFF      R_AARCH64_TLS_DTPREL64
+#define REL_TPOFF       R_AARCH64_TLS_TPREL64
+#define REL_TLSDESC     R_AARCH64_TLSDESC
+
+#define CRTJMP(pc,sp) __asm__ __volatile__( \
+	"mov sp,%1 ; bx %0" : : "r"(pc), "r"(sp) : "memory" )

arch/arm/crt_arch.h

@@ -1,10 +1,15 @@
-__asm__("\
-.global _start \n\
-.type _start,%function \n\
-_start: \n\
-	mov fp, #0 \n\
-	mov lr, #0 \n\
-	mov a1, sp \n\
-	and sp, sp, #-16 \n\
-	bl __cstart \n\
-");
+__asm__(
+".global " START " \n"
+".type " START ",%function \n"
+START ": \n"
+"	mov fp, #0 \n"
+"	mov lr, #0 \n"
+"	mov a1, sp \n"
+"	ldr a2, 1f \n"
+"2:	add a2, pc, a2 \n"
+"	and sp, sp, #-16 \n"
+"	bl " START "_c \n"
+".weak _DYNAMIC \n"
+".hidden _DYNAMIC \n"
+"1:	.word _DYNAMIC-2b-8 \n"
+);

arch/arm/reloc.h

@@ -1,5 +1,3 @@
-#include <string.h>
-#include <elf.h>
 #include <endian.h>
 
 #if __BYTE_ORDER == __BIG_ENDIAN
@@ -20,25 +18,15 @@
 
 #define TPOFF_K 8
 
-static int remap_rel(int type)
-{
-	switch(type) {
-	case R_ARM_ABS32:
-		return REL_SYMBOLIC;
-	case R_ARM_GLOB_DAT:
-		return REL_GOT;
-	case R_ARM_JUMP_SLOT:
-		return REL_PLT;
-	case R_ARM_RELATIVE:
-		return REL_RELATIVE;
-	case R_ARM_COPY:
-		return REL_COPY;
-	case R_ARM_TLS_DTPMOD32:
-		return REL_DTPMOD;
-	case R_ARM_TLS_DTPOFF32:
-		return REL_DTPOFF;
-	case R_ARM_TLS_TPOFF32:
-		return REL_TPOFF;
-	}
-	return 0;
-}
+#define REL_SYMBOLIC    R_ARM_ABS32
+#define REL_GOT         R_ARM_GLOB_DAT
+#define REL_PLT         R_ARM_JUMP_SLOT
+#define REL_RELATIVE    R_ARM_RELATIVE
+#define REL_COPY        R_ARM_COPY
+#define REL_DTPMOD      R_ARM_TLS_DTPMOD32
+#define REL_DTPOFF      R_ARM_TLS_DTPOFF32
+#define REL_TPOFF       R_ARM_TLS_TPOFF32
+//#define REL_TLSDESC     R_ARM_TLS_DESC
+
+#define CRTJMP(pc,sp) __asm__ __volatile__( \
+	"mov sp,%1 ; tst %0,#1 ; moveq pc,%0 ; bx %0" : : "r"(pc), "r"(sp) : "memory" )

arch/i386/crt_arch.h

@@ -1,13 +1,16 @@
-__asm__("\
-.text \n\
-.global _start \n\
-_start: \n\
-	xor %ebp,%ebp \n\
-	mov %esp,%eax \n\
-	and $-16,%esp \n\
-	push %eax \n\
-	push %eax \n\
-	push %eax \n\
-	push %eax \n\
-	call __cstart \n\
-");
+__asm__(
+".text\n"
+".weak _DYNAMIC \n"
+".hidden _DYNAMIC \n"
+".global " START "\n"
+START ":\n"
+"	xor %ebp,%ebp \n"
+"	mov %esp,%eax \n"
+"	and $-16,%esp \n"
+"	push %eax \n"
+"	push %eax \n"
+"	call 1f \n"
+"1:	addl $_DYNAMIC-1b,(%esp) \n"
+"	push %eax \n"
+"	call " START "_c \n"
+);

arch/i386/reloc.h

@@ -1,33 +1,16 @@
-#include <string.h>
-#include <elf.h>
-
 #define LDSO_ARCH "i386"
 
-static int remap_rel(int type)
-{
-	switch(type) {
-	case R_386_32:
-		return REL_SYMBOLIC;
-	case R_386_PC32:
-		return REL_OFFSET;
-	case R_386_GLOB_DAT:
-		return REL_GOT;
-	case R_386_JMP_SLOT:
-		return REL_PLT;
-	case R_386_RELATIVE:
-		return REL_RELATIVE;
-	case R_386_COPY:
-		return REL_COPY;
-	case R_386_TLS_DTPMOD32:
-		return REL_DTPMOD;
-	case R_386_TLS_DTPOFF32:
-		return REL_DTPOFF;
-	case R_386_TLS_TPOFF:
-		return REL_TPOFF;
-	case R_386_TLS_TPOFF32:
-		return REL_TPOFF_NEG;
-	case R_386_TLS_DESC:
-		return REL_TLSDESC;
-	}
-	return 0;
-}
+#define REL_SYMBOLIC    R_386_32
+#define REL_OFFSET      R_386_PC32
+#define REL_GOT         R_386_GLOB_DAT
+#define REL_PLT         R_386_JMP_SLOT
+#define REL_RELATIVE    R_386_RELATIVE
+#define REL_COPY        R_386_COPY
+#define REL_DTPMOD      R_386_TLS_DTPMOD32
+#define REL_DTPOFF      R_386_TLS_DTPOFF32
+#define REL_TPOFF       R_386_TLS_TPOFF
+#define REL_TPOFF_NEG   R_386_TLS_TPOFF32
+#define REL_TLSDESC     R_386_TLS_DESC
+
+#define CRTJMP(pc,sp) __asm__ __volatile__( \
+	"mov %1,%%esp ; jmp *%0" : : "r"(pc), "r"(sp) : "memory" )

arch/microblaze/crt_arch.h

@@ -1,11 +1,16 @@
-__asm__("\
-.global _start \n\
-.align  2 \n\
-_start: \n\
-	add r19, r0, r0 \n\
-	ori r5, r1, 0 \n\
-	andi r1, r1, -8 \n\
-	addik r1, r1, -8 \n\
-	bri __cstart \n\
-	nop \n\
-");
+__asm__(
+".global " START " \n"
+".align  2 \n"
+START ": \n"
+"	add r19, r0, r0 \n"
+"	ori r5, r1, 0 \n"
+"1:	mfs r6, rpc \n"
+".weak _DYNAMIC \n"
+".hidden _DYNAMIC \n"
+"	addik r6, r6, _GLOBAL_OFFSET_TABLE_+8 \n"
+"	addik r6, r6, _DYNAMIC@GOTOFF \n"
+"	andi r1, r1, -8 \n"
+"	addik r1, r1, -8 \n"
+"	bri " START "_c \n"
+"	nop \n"
+);

arch/microblaze/reloc.h

@@ -1,5 +1,3 @@
-#include <string.h>
-#include <elf.h>
 #include <endian.h>
 
 #if __BYTE_ORDER == __LITTLE_ENDIAN
@@ -12,40 +10,13 @@
 
 #define TPOFF_K 0
 
-static int remap_rel(int type)
-{
-	switch(type) {
-	case R_MICROBLAZE_32:
-		return REL_SYMBOLIC;
-	case R_MICROBLAZE_GLOB_DAT:
-		return REL_GOT;
-	case R_MICROBLAZE_JUMP_SLOT:
-		return REL_PLT;
-	case R_MICROBLAZE_REL:
-		return REL_RELATIVE;
-	case R_MICROBLAZE_COPY:
-		return REL_COPY;
-	case R_MICROBLAZE_TLSDTPMOD32:
-		return REL_DTPMOD;
-	case R_MICROBLAZE_TLSDTPREL32:
-		return REL_DTPOFF;
-	}
-	return 0;
-}
+#define REL_SYMBOLIC    R_MICROBLAZE_32
+#define REL_GOT         R_MICROBLAZE_GLOB_DAT
+#define REL_PLT         R_MICROBLAZE_JUMP_SLOT
+#define REL_RELATIVE    R_MICROBLAZE_REL
+#define REL_COPY        R_MICROBLAZE_COPY
+#define REL_DTPMOD      R_MICROBLAZE_TLSDTPMOD32
+#define REL_DTPOFF      R_MICROBLAZE_TLSDTPREL32
 
-#include "syscall.h"
-void __reloc_self(int c, size_t *a, size_t *dynv)
-{
-	char dot = '.', ex = 'x';
-	char *base;
-	size_t t[20], n;
-	for (a+=c+1; *a; a++);
-	for (a++; *a; a+=2) if (*a<20) t[*a] = a[1];
-	base = (char *)t[AT_BASE];
-	if (!base) base = (char *)(t[AT_PHDR] & -t[AT_PAGESZ]);
-	for (a=dynv; *a; a+=2) if (*a<20) t[*a] = a[1];
-	n = t[DT_RELASZ];
-	for (a=(void *)(base+t[DT_RELA]); n; a+=3, n-=12)
-		if (a[1]%256 == R_MICROBLAZE_REL)
-			*(size_t *)(base+a[0]) = (size_t)base + a[2];
-}
+#define CRTJMP(pc,sp) __asm__ __volatile__( \
+	"addik r1,%1,0 ; bra %0" : : "r"(pc), "r"(sp) : "memory" )

arch/mips/crt_arch.h

@@ -1,21 +1,28 @@
-__asm__("\n\
-.set push\n\
-.set noreorder\n\
-.global __start\n\
-.global _start\n\
-.type   __start, @function\n\
-.type   _start, @function\n\
-__start:\n\
-_start:\n\
-	bal 1f \n\
-	move $fp, $0 \n\
-2:	.gpword 2b \n\
-1:	lw $gp, 0($ra) \n\
-	subu $gp, $ra, $gp \n\
-	move $4, $sp \n\
-	subu $sp, $sp, 16 \n\
-	and $sp, $sp, -8 \n\
-	lw $25, %call16(__cstart)($gp) \n\
-	jalr $25 \n\
-	nop \n\
-.set pop");
+__asm__(
+".set push\n"
+".set noreorder\n"
+".global _" START "\n"
+".global " START "\n"
+".type   _" START ", @function\n"
+".type   " START ", @function\n"
+"_" START ":\n"
+"" START ":\n"
+"	bal 1f \n"
+"	 move $fp, $0 \n"
+"2:	.gpword 2b \n"
+	.gpword " START "_c \n"
+".weak _DYNAMIC \n"
+".hidden _DYNAMIC \n"
+"	.gpword _DYNAMIC \n"
+"1:	lw $gp, 0($ra) \n"
+"	subu $gp, $ra, $gp \n"
+"	move $4, $sp \n"
+"	lw $5, 8($ra) \n"
+"	addu $5, $5, $gp \n"
+"	lw $25, 4($ra) \n"
+"	addu $25, $25, $gp \n"
+"	subu $sp, $sp, 16 \n"
+"	jalr $25 \n"
+"	 and $sp, $sp, -8 \n"
+".set pop \n"
+);

arch/mips/reloc.h

@@ -1,5 +1,3 @@
-#include <string.h>
-#include <elf.h>
 #include <endian.h>
 
 #if __BYTE_ORDER == __LITTLE_ENDIAN
@@ -18,72 +16,16 @@
 
 #define TPOFF_K (-0x7000)
 
-static int remap_rel(int type)
-{
-	switch(type) {
-	case R_MIPS_REL32:
-		return REL_SYM_OR_REL;
-	case R_MIPS_JUMP_SLOT:
-		return REL_PLT;
-	case R_MIPS_COPY:
-		return REL_COPY;
-	case R_MIPS_TLS_DTPMOD32:
-		return REL_DTPMOD;
-	case R_MIPS_TLS_DTPREL32:
-		return REL_DTPOFF;
-	case R_MIPS_TLS_TPREL32:
-		return REL_TPOFF;
-	}
-	return 0;
-}
+#define REL_SYM_OR_REL  R_MIPS_REL32
+#define REL_PLT         R_MIPS_JUMP_SLOT
+#define REL_COPY        R_MIPS_COPY
+#define REL_DTPMOD      R_MIPS_TLS_DTPMOD32
+#define REL_DTPOFF      R_MIPS_TLS_DTPREL32
+#define REL_TPOFF       R_MIPS_TLS_TPREL32
 
-void __reloc_self(int c, size_t *a, size_t *dynv, size_t *got)
-{
-	char *base;
-	size_t t[20], n;
-	for (a+=c+1; *a; a++);
-	for (a++; *a; a+=2) if (*a<20) t[*a] = a[1];
-	base = (char *)t[AT_BASE];
-	if (!base) base = (char *)(t[AT_PHDR] & -t[AT_PAGESZ]);
-	for (a=dynv; *a; a+=2) if (*a-0x70000000UL<20) t[*a&31] = a[1];
-	n = t[DT_MIPS_LOCAL_GOTNO - 0x70000000];
-	for (a=got; n; a++, n--) *a += (size_t)base;
-}
-
-static void do_relocs(struct dso *dso, size_t *rel, size_t rel_size, size_t stride);
-
-static void do_arch_relocs(struct dso *this, struct dso *head)
-{
-	unsigned char *base = this->base;
-	size_t *dynv = this->dynv;
-	size_t dyn[20] = {0};
-	size_t i;
-	size_t rel[2], got=0;
-	Sym *sym;
-
-	for (i=0; dynv[i]; i+=2) {
-		if (dynv[i]-0x70000000UL<20)
-			dyn[dynv[i]&31] = dynv[i+1];
-		else if (dynv[i] == DT_PLTGOT)
-			got = dynv[i+1];
-	}
-	i = dyn[DT_MIPS_LOCAL_GOTNO-0x70000000];
-	if (this->shortname && !strcmp(this->shortname, "libc.so")) {
-		got += sizeof(size_t) * i;
-	} else {
-		for (; i; i--, got+=sizeof(size_t))
-			*(size_t *)(base+got) += (size_t)base;
-	}
-	sym = this->syms + dyn[DT_MIPS_GOTSYM-0x70000000];
-	i = dyn[DT_MIPS_SYMTABNO-0x70000000] - dyn[DT_MIPS_GOTSYM-0x70000000];
-	for (; i; i--, got+=sizeof(size_t), sym++) {
-		rel[0] = got;
-		rel[1] = sym-this->syms << 8 | R_MIPS_JUMP_SLOT;
-		*(size_t *)(base+got) = 0;
-		do_relocs(this, rel, sizeof rel, 2);
-	}
-}
-
-#define NEED_ARCH_RELOCS 1
+#define NEED_MIPS_GOT_RELOCS 1
 #define DYNAMIC_IS_RO 1
 #define ARCH_SYM_REJECT_UND(s) (!((s)->st_other & STO_MIPS_PLT))
+
+#define CRTJMP(pc,sp) __asm__ __volatile__( \
+	"move $sp,%1 ; jr %0" : : "r"(pc), "r"(sp) : "memory" )

arch/or1k/crt_arch.h

@@ -1,11 +1,17 @@
-__asm__("\
-.global _start \n\
-.align  4 \n\
-_start: \n\
-	l.ori r3, r1, 0 \n\
-	l.addi r2, r0, -8 \n\
-	l.and r1, r1, r2 \n\
-	l.addi r1, r1, -8 \n\
-	l.jal __cstart \n\
-	 l.ori r2, r0, 0 \n\
-");
+__asm__(
+".global " START " \n"
+".align  4 \n"
+START ": \n"
+"	l.jal 1f \n"
+"	 l.ori r3, r1, 0 \n"
+".weak _DYNAMIC \n"
+".hidden _DYNAMIC \n"
+"	.word _DYNAMIC-. \n"
+"1:	l.lwz r4, 0(r9) \n"
+"	l.add r4, r4, r9 \n"
+"	l.addi r2, r0, -8 \n"
+"	l.and r1, r1, r2 \n"
+"	l.addi r1, r1, -16 \n"
+"	l.jal " START "_c \n"
+"	 l.ori r2, r0, 0 \n"
+);

arch/or1k/reloc.h

@@ -1,47 +1,15 @@
-#include <string.h>
-#include <elf.h>
-#include <endian.h>
-
 #define LDSO_ARCH "or1k"
 
 #define TPOFF_K 0
 
-static int remap_rel(int type)
-{
-	switch(type) {
-	case R_OR1K_32:
-		return REL_SYMBOLIC;
-	case R_OR1K_GLOB_DAT:
-		return REL_GOT;
-	case R_OR1K_JMP_SLOT:
-		return REL_PLT;
-	case R_OR1K_RELATIVE:
-		return REL_RELATIVE;
-	case R_OR1K_COPY:
-		return REL_COPY;
-	case R_OR1K_TLS_DTPMOD:
-		return REL_DTPMOD;
-	case R_OR1K_TLS_DTPOFF:
-		return REL_DTPOFF;
-	case R_OR1K_TLS_TPOFF:
-		return REL_TPOFF;
-	}
-	return 0;
-}
-
-#include "syscall.h"
-void __reloc_self(int c, size_t *a, size_t *dynv)
-{
-	char dot = '.', ex = 'x';
-	char *base;
-	size_t t[20], n;
-	for (a+=c+1; *a; a++);
-	for (a++; *a; a+=2) if (*a<20) t[*a] = a[1];
-	base = (char *)t[AT_BASE];
-	if (!base) base = (char *)(t[AT_PHDR] & -t[AT_PAGESZ]);
-	for (a=dynv; *a; a+=2) if (*a<20) t[*a] = a[1];
-	n = t[DT_RELASZ];
-	for (a=(void *)(base+t[DT_RELA]); n; a+=3, n-=12)
-		if (a[1]%256 == R_OR1K_RELATIVE)
-			*(size_t *)(base+a[0]) = (size_t)base + a[2];
-}
+#define REL_SYMBOLIC    R_OR1K_32
+#define REL_GOT         R_OR1K_GLOB_DAT
+#define REL_PLT         R_OR1K_JMP_SLOT
+#define REL_RELATIVE    R_OR1K_RELATIVE
+#define REL_COPY        R_OR1K_COPY
+#define REL_DTPMOD      R_OR1K_TLS_DTPMOD
+#define REL_DTPOFF      R_OR1K_TLS_DTPOFF
+#define REL_TPOFF       R_OR1K_TLS_TPOFF
+
+#define CRTJMP(pc,sp) __asm__ __volatile__( \
+	"l.jr %0 ; l.ori r1,%1,0" : : "r"(pc), "r"(sp) : "memory" )

arch/powerpc/crt_arch.h

@@ -1,12 +1,19 @@
-__asm__("\
-.global _start \n\
-.type   _start, %function \n\
-_start: \n\
-	mr 3, 1 \n\
-	clrrwi 1, 1, 4 \n\
-	li 0, 0 \n\
-	stwu 1, -16(1) \n\
-	mtlr 0 \n\
-	stw 0, 0(1) \n\
-	bl __cstart \n\
-");        
+__asm__(
+".global " START " \n"
+".type   " START ", %function \n"
+START ": \n"
+"	bl 1f \n"
+".weak _DYNAMIC \n"
+".hidden _DYNAMIC \n"
+"	.long _DYNAMIC-. \n"
+"1:	mflr 4 \n"
+"	lwz 3, 0(4) \n"
+"	add 4, 3, 4 \n"
+"	mr 3, 1 \n"
+"	clrrwi 1, 1, 4 \n"
+"	li 0, 0 \n"
+"	stwu 1, -16(1) \n"
+"	mtlr 0 \n"
+"	stw 0, 0(1) \n"
+"	bl " START "_c \n"
+);

arch/powerpc/reloc.h

@@ -1,44 +1,15 @@
-#include <string.h>
-#include <elf.h>
-
 #define LDSO_ARCH "powerpc"
 
 #define TPOFF_K (-0x7000)
 
-static int remap_rel(int type)
-{
-	switch(type) {
-	case R_PPC_ADDR32:
-		return REL_SYMBOLIC;
-	case R_PPC_GLOB_DAT:
-		return REL_GOT;
-	case R_PPC_JMP_SLOT:
-		return REL_PLT;
-	case R_PPC_RELATIVE:
-		return REL_RELATIVE;
-	case R_PPC_COPY:
-		return REL_COPY;
-	case R_PPC_DTPMOD32:
-		return REL_DTPMOD;
-	case R_PPC_DTPREL32:
-		return REL_DTPOFF;
-	case R_PPC_TPREL32:
-		return REL_TPOFF;
-	}
-	return 0;
-}
-
-void __reloc_self(int c, size_t *a, size_t *dynv)
-{
-	char *base;
-	size_t t[20], n;
-	for (a+=c+1; *a; a++);
-	for (a++; *a; a+=2) if (*a<20) t[*a] = a[1];
-	base = (char *)t[AT_BASE];
-	if (!base) base = (char *)(t[AT_PHDR] & -t[AT_PAGESZ]);
-	for (a=dynv; *a; a+=2) if (*a<20) t[*a] = a[1];
-	n = t[DT_RELASZ];
-	for (a=(void *)(base+t[DT_RELA]); n; a+=3, n-=12)
-		if (a[1]%256 == R_PPC_RELATIVE)
-			*(size_t *)(base+a[0]) = (size_t)base + a[2];
-}
+#define REL_SYMBOLIC    R_PPC_ADDR32
+#define REL_GOT         R_PPC_GLOB_DAT
+#define REL_PLT         R_PPC_JMP_SLOT
+#define REL_RELATIVE    R_PPC_RELATIVE
+#define REL_COPY        R_PPC_COPY
+#define REL_DTPMOD      R_PPC_DTPMOD32
+#define REL_DTPOFF      R_PPC_DTPREL32
+#define REL_TPOFF       R_PPC_TPREL32
+
+#define CRTJMP(pc,sp) __asm__ __volatile__( \
+	"mr 1,%1 ; mtlr %0 ; blr" : : "r"(pc), "r"(sp) : "memory" )

arch/sh/crt_arch.h

@@ -1,12 +1,22 @@
-__asm__("\
-.global _start \n\
-_start: \n\
-	mov r15, r4 \n\
-	mov #-16, r0 \n\
-	and r0, r15 \n\
-	bsr __cstart \n\
-	nop \n\
-");
+__asm__(
+".global " START " \n"
+START ": \n"
+"	mova 1f, r0 \n"
+"	mov.l 1f, r5 \n"
+"	add r0, r5 \n"
+"	mov r15, r4 \n"
+"	mov #-16, r0 \n"
+"	and r0, r15 \n"
+"	bsr " START "_c \n"
+"	nop \n"
+".align 2 \n"
+".weak _DYNAMIC \n"
+".hidden _DYNAMIC \n"
+"1:	.long _DYNAMIC-. \n"
+);
 
 /* used by gcc for switching the FPU between single and double precision */
+#ifdef SHARED
+__attribute__((__visibility__("hidden")))
+#endif
 const unsigned long __fpscr_values[2] = { 0, 0x80000 };

arch/sh/reloc.h

@@ -8,27 +8,15 @@
 
 #define TPOFF_K 8
 
-static int remap_rel(int type)
-{
-	switch(type) {
-	case R_SH_DIR32:
-		return REL_SYMBOLIC;
-	case R_SH_REL32:
-		return REL_OFFSET;
-	case R_SH_GLOB_DAT:
-		return REL_GOT;
-	case R_SH_JMP_SLOT:
-		return REL_PLT;
-	case R_SH_RELATIVE:
-		return REL_RELATIVE;
-	case R_SH_COPY:
-		return REL_COPY;
-	case R_SH_TLS_DTPMOD32:
-		return REL_DTPMOD;
-	case R_SH_TLS_DTPOFF32:
-		return REL_DTPOFF;
-	case R_SH_TLS_TPOFF32:
-		return REL_TPOFF;
-	}
-	return 0;
-}
+#define REL_SYMBOLIC    R_SH_DIR32
+#define REL_OFFSET      R_SH_REL32
+#define REL_GOT         R_SH_GLOB_DAT
+#define REL_PLT         R_SH_JMP_SLOT
+#define REL_RELATIVE    R_SH_RELATIVE
+#define REL_COPY        R_SH_COPY
+#define REL_DTPMOD      R_SH_TLS_DTPMOD32
+#define REL_DTPOFF      R_SH_TLS_DTPOFF32
+#define REL_TPOFF       R_SH_TLS_TPOFF32
+
+#define CRTJMP(pc,sp) __asm__ __volatile__( \
+	"jmp @%0 ; mov %1,r15" : : "r"(pc), "r"(sp) : "memory" )

arch/sh/src/__fpscr_values.c

@@ -1,5 +1,5 @@
 #include "libc.h"
 
 /* used by gcc for switching the FPU between single and double precision */
-const unsigned long __fpscr_values[2] ATTR_LIBC_VISIBILITY = { 0, 0x80000 };
+//const unsigned long __fpscr_values[2] ATTR_LIBC_VISIBILITY = { 0, 0x80000 };
 

arch/x32/crt_arch.h

@@ -1,9 +1,12 @@
-__asm__("\
-.text \n\
-.global _start \n\
-_start: \n\
-	xor %rbp,%rbp \n\
-	mov %rsp,%rdi \n\
-	andq $-16,%rsp \n\
-	call __cstart \n\
-");
+__asm__(
+".text \n"
+".global " START " \n"
+START ": \n"
+"	xor %rbp,%rbp \n"
+"	mov %rsp,%rdi \n"
+".weak _DYNAMIC \n"
+".hidden _DYNAMIC \n"
+"	lea _DYNAMIC(%rip),%rsi \n"
+"	andq $-16,%rsp \n"
+"	call " START "_c \n"
+);

arch/x32/reloc.h

@@ -1,7 +1,3 @@
-#include <stdint.h>
-#include <string.h>
-#include <elf.h>
-
 #define LDSO_ARCH "x32"
 
 /* FIXME: x32 is very strange in its use of 64-bit relocation types in
@@ -11,30 +7,20 @@
  * checked. In particular, R_X86_64_64, R_X86_64_DTPOFF64, and
  * R_X86_64_TPOFF64 may need checking. */
 
-static int remap_rel(int type)
-{
-	switch(type) {
-	case R_X86_64_64:
-	case R_X86_64_32:
-		return REL_SYMBOLIC;
-	case R_X86_64_PC32:
-		return REL_OFFSET;
-	case R_X86_64_GLOB_DAT:
-		return REL_GOT;
-	case R_X86_64_JUMP_SLOT:
-		return REL_PLT;
-	case R_X86_64_RELATIVE:
-		return REL_RELATIVE;
-	case R_X86_64_COPY:
-		return REL_COPY;
-	case R_X86_64_DTPMOD64:
-		return REL_DTPMOD;
-	case R_X86_64_DTPOFF64:
-	case R_X86_64_DTPOFF32:
-		return REL_DTPOFF;
-	case R_X86_64_TPOFF64:
-	case R_X86_64_TPOFF32:
-		return REL_TPOFF;
-	}
-	return 0;
-}
+/* The R_X86_64_64, R_X86_64_DTPOFF32, and R_X86_64_TPOFF32 reloc types
+ * were previously mapped in the switch table form of this file; however,
+ * they do not seem to be used/usable for anything. If needed, new
+ * mappings will have to be added. */
+
+#define REL_SYMBOLIC    R_X86_64_32
+#define REL_OFFSET      R_X86_64_PC32
+#define REL_GOT         R_X86_64_GLOB_DAT
+#define REL_PLT         R_X86_64_JUMP_SLOT
+#define REL_RELATIVE    R_X86_64_RELATIVE
+#define REL_COPY        R_X86_64_COPY
+#define REL_DTPMOD      R_X86_64_DTPMOD64
+#define REL_DTPOFF      R_X86_64_DTPOFF64
+#define REL_TPOFF       R_X86_64_TPOFF64
+
+#define CRTJMP(pc,sp) __asm__ __volatile__( \
+	"mov %1,%%esp ; jmp *%0" : : "r"(pc), "r"(sp) : "memory" )

arch/x86_64/crt_arch.h

@@ -1,9 +1,12 @@
-__asm__("\
-.text \n\
-.global _start \n\
-_start: \n\
-	xor %rbp,%rbp \n\
-	mov %rsp,%rdi \n\
-	andq $-16,%rsp \n\
-	call __cstart \n\
-");
+__asm__(
+".text \n"
+".global " START " \n"
+START ": \n"
+"	xor %rbp,%rbp \n"
+"	mov %rsp,%rdi \n"
+".weak _DYNAMIC \n"
+".hidden _DYNAMIC \n"
+"	lea _DYNAMIC(%rip),%rsi \n"
+"	andq $-16,%rsp \n"
+"	call " START "_c \n"
+);

arch/x86_64/reloc.h

@@ -1,32 +1,15 @@
-#include <stdint.h>
-#include <string.h>
-#include <elf.h>
-
 #define LDSO_ARCH "x86_64"
 
-static int remap_rel(int type)
-{
-	switch(type) {
-	case R_X86_64_64:
-		return REL_SYMBOLIC;
-	case R_X86_64_PC32:
-		return REL_OFFSET32;
-	case R_X86_64_GLOB_DAT:
-		return REL_GOT;
-	case R_X86_64_JUMP_SLOT:
-		return REL_PLT;
-	case R_X86_64_RELATIVE:
-		return REL_RELATIVE;
-	case R_X86_64_COPY:
-		return REL_COPY;
-	case R_X86_64_DTPMOD64:
-		return REL_DTPMOD;
-	case R_X86_64_DTPOFF64:
-		return REL_DTPOFF;
-	case R_X86_64_TPOFF64:
-		return REL_TPOFF;
-	case R_X86_64_TLSDESC:
-		return REL_TLSDESC;
-	}
-	return 0;
-}
+#define REL_SYMBOLIC    R_X86_64_64
+#define REL_OFFSET32    R_X86_64_PC32
+#define REL_GOT         R_X86_64_GLOB_DAT
+#define REL_PLT         R_X86_64_JUMP_SLOT
+#define REL_RELATIVE    R_X86_64_RELATIVE
+#define REL_COPY        R_X86_64_COPY
+#define REL_DTPMOD      R_X86_64_DTPMOD64
+#define REL_DTPOFF      R_X86_64_DTPOFF64
+#define REL_TPOFF       R_X86_64_TPOFF64
+#define REL_TLSDESC     R_X86_64_TLSDESC
+
+#define CRTJMP(pc,sp) __asm__ __volatile__( \
+	"mov %1,%%rsp ; jmp *%0" : : "r"(pc), "r"(sp) : "memory" )

crt/crt1.c

@@ -1,5 +1,7 @@
 #include <features.h>
 
+#define START "_start"
+
 #include "crt_arch.h"
 
 int main();
@@ -8,7 +10,7 @@ void _fini() __attribute__((weak));
 _Noreturn int __libc_start_main(int (*)(), int, char **,
 	void (*)(), void(*)(), void(*)());
 
-void __cstart(long *p)
+void _start_c(long *p)
 {
 	int argc = p[0];
 	char **argv = (void *)(p+1);

src/internal/dynlink.h

@@ -0,0 +1,57 @@
+#ifndef _INTERNAL_RELOC_H
+#define _INTERNAL_RELOC_H
+
+#include <features.h>
+#include <elf.h>
+#include <stdint.h>
+
+#if UINTPTR_MAX == 0xffffffff
+typedef Elf32_Ehdr Ehdr;
+typedef Elf32_Phdr Phdr;
+typedef Elf32_Sym Sym;
+#define R_TYPE(x) ((x)&255)
+#define R_SYM(x) ((x)>>8)
+#else
+typedef Elf64_Ehdr Ehdr;
+typedef Elf64_Phdr Phdr;
+typedef Elf64_Sym Sym;
+#define R_TYPE(x) ((x)&0x7fffffff)
+#define R_SYM(x) ((x)>>32)
+#endif
+
+/* These enum constants provide unmatchable default values for
+ * any relocation type the arch does not use. */
+enum {
+	REL_NONE = 0,
+	REL_SYMBOLIC = -100,
+	REL_GOT,
+	REL_PLT,
+	REL_RELATIVE,
+	REL_OFFSET,
+	REL_OFFSET32,
+	REL_COPY,
+	REL_SYM_OR_REL,
+	REL_DTPMOD,
+	REL_DTPOFF,
+	REL_TPOFF,
+	REL_TPOFF_NEG,
+	REL_TLSDESC,
+};
+
+#include "reloc.h"
+
+#define IS_RELATIVE(x) ( \
+	(R_TYPE(x) == REL_RELATIVE) || \
+	(R_TYPE(x) == REL_SYM_OR_REL && !R_SYM(x)) )
+
+#ifndef NEED_MIPS_GOT_RELOCS
+#define NEED_MIPS_GOT_RELOCS 0
+#endif
+
+#define AUX_CNT 32
+#define DYN_CNT 32
+
+typedef void (*stage2_func)(unsigned char *);
+typedef _Noreturn void (*stage3_func)(size_t *);
+
+#endif

src/ldso/aarch64/start.s

@@ -1,18 +0,0 @@
-.global _dlstart
-_dlstart:
-	ldr x0,[sp]
-	add x1,sp,#8
-	bl __dynlink
-	mov x1,sp
-	ldr x2,[x1],#8
-1:	sub x2,x2,1
-	ldr x3,[x1],#8
-	cmn x3,#1
-	b.eq 1b
-	add x2,x2,1
-	str x3,[x1,#-8]!
-	str x2,[x1,#-8]!
-	mov sp,x1
-	mov x1,x0
-	mov x0,#0
-	blr x1

src/ldso/arm/start.s

@@ -1,18 +0,0 @@
-.text
-.global _dlstart
-_dlstart:
-	ldr r0,[sp]
-	add r1,sp,#4
-	bl __dynlink
-	pop {r1}
-1:	sub r1,r1,#1
-	pop {r2}
-	cmp r2,#-1
-	beq 1b
-	add r1,r1,#1
-	push {r1,r2}
-	mov r1,r0
-	mov r0,#0
-	tst r1,#1
-	moveq pc,r1
-	bx r1

src/ldso/dlstart.c

@@ -0,0 +1,107 @@
+#include <stddef.h>
+#include "dynlink.h"
+
+#ifdef SHARED
+
+#ifndef START
+#define START "_dlstart"
+#endif
+
+#include "crt_arch.h"
+
+void _dlstart_c(size_t *sp, size_t *dynv)
+{
+	size_t i, aux[AUX_CNT], dyn[DYN_CNT];
+
+	int argc = *sp;
+	char **argv = (void *)(sp+1);
+
+	for (i=argc+1; argv[i]; i++);
+	size_t *auxv = (void *)(argv+i+1);
+
+	for (i=0; i<AUX_CNT; i++) aux[i] = 0;
+	for (i=0; auxv[i]; i+=2) if (auxv[i]<AUX_CNT)
+		aux[auxv[i]] = auxv[i+1];
+
+	for (i=0; i<DYN_CNT; i++) dyn[i] = 0;
+	for (i=0; dynv[i]; i+=2) if (dynv[i]<DYN_CNT)
+		dyn[dynv[i]] = dynv[i+1];
+
+	/* If the dynamic linker is invoked as a command, its load
+	 * address is not available in the aux vector. Instead, compute
+	 * the load address as the difference between &_DYNAMIC and the
+	 * virtual address in the PT_DYNAMIC program header. */
+	unsigned char *base = (void *)aux[AT_BASE];
+	if (!base) {
+		size_t phnum = aux[AT_PHNUM];
+		size_t phentsize = aux[AT_PHENT];
+		Phdr *ph = (void *)aux[AT_PHDR];
+		for (i=phnum; i--; ph = (void *)((char *)ph + phentsize)) {
+			if (ph->p_type == PT_DYNAMIC) {
+				base = (void *)((size_t)dynv - ph->p_vaddr);
+				break;
+			}
+		}
+	}
+
+	/* MIPS uses an ugly packed form for GOT relocations. Since we
+	 * can't make function calls yet and the code is tiny anyway,
+	 * it's simply inlined here. */
+	if (NEED_MIPS_GOT_RELOCS) {
+		size_t local_cnt = 0;
+		size_t *got = (void *)(base + dyn[DT_PLTGOT]);
+		for (i=0; dynv[i]; i+=2) if (dynv[i]==DT_MIPS_LOCAL_GOTNO)
+			local_cnt = dynv[i+1];
+		for (i=0; i<local_cnt; i++) got[i] += (size_t)base;
+	}
+
+	/* The use of the reloc_info structure and nested loops is a trick
+	 * to work around the fact that we can't necessarily make function
+	 * calls yet. Each struct in the array serves like the arguments
+	 * to a function call. */
+	struct {
+		void *rel;
+		size_t size;
+		size_t stride;
+	} reloc_info[] = {
+		{ base+dyn[DT_JMPREL], dyn[DT_PLTRELSZ], 2+(dyn[DT_PLTREL]==DT_RELA) },
+		{ base+dyn[DT_REL], dyn[DT_RELSZ], 2 },
+		{ base+dyn[DT_RELA], dyn[DT_RELASZ], 3 },
+		{ 0, 0, 0 }
+	};
+
+	for (i=0; reloc_info[i].stride; i++) {
+		size_t *rel = reloc_info[i].rel;
+		size_t rel_size = reloc_info[i].size;
+		size_t stride = reloc_info[i].stride;
+		for (; rel_size; rel+=stride, rel_size-=stride*sizeof(size_t)) {
+			if (!IS_RELATIVE(rel[1])) continue;
+			size_t *rel_addr = (void *)(base + rel[0]);
+			size_t addend = stride==3 ? rel[2] : *rel_addr;
+			*rel_addr = (size_t)base + addend;
+		}
+	}
+
+	const char *strings = (void *)(base + dyn[DT_STRTAB]);
+	const Sym *syms = (void *)(base + dyn[DT_SYMTAB]);
+
+	/* Call dynamic linker stage-2, __dls2 */
+	for (i=0; ;i++) {
+		const char *s = strings + syms[i].st_name;
+		if (s[0]=='_' && s[1]=='_' && s[2]=='d'
+		 && s[3]=='l' && s[4]=='s' && s[5]=='2' && !s[6])
+			break;
+	}
+	((stage2_func)(base + syms[i].st_value))(base);
+
+	/* Call dynamic linker stage-3, __dls3 */
+	for (i=0; ;i++) {
+		const char *s = strings + syms[i].st_name;
+		if (s[0]=='_' && s[1]=='_' && s[2]=='d'
+		 && s[3]=='l' && s[4]=='s' && s[5]=='3' && !s[6])
+			break;
+	}
+	((stage3_func)(base + syms[i].st_value))(sp);
+}
+
+#endif

src/ldso/dynlink.c

@@ -19,26 +19,13 @@
 #include <dlfcn.h>
 #include "pthread_impl.h"
 #include "libc.h"
+#include "dynlink.h"
 
 static int errflag;
 static char errbuf[128];
 
 #ifdef SHARED
 
-#if ULONG_MAX == 0xffffffff
-typedef Elf32_Ehdr Ehdr;
-typedef Elf32_Phdr Phdr;
-typedef Elf32_Sym Sym;
-#define R_TYPE(x) ((x)&255)
-#define R_SYM(x) ((x)>>8)
-#else
-typedef Elf64_Ehdr Ehdr;
-typedef Elf64_Phdr Phdr;
-typedef Elf64_Sym Sym;
-#define R_TYPE(x) ((x)&0xffffffff)
-#define R_SYM(x) ((x)>>32)
-#endif
-
 #define MAXP2(a,b) (-(-(a)&-(b)))
 #define ALIGN(x,y) ((x)+(y)-1 & -(y))
 
@@ -88,6 +75,7 @@ struct dso {
 	volatile int new_dtv_idx, new_tls_idx;
 	struct td_index *td_index;
 	struct dso *fini_next;
+	int rel_early_relative, rel_update_got;
 	char *shortname;
 	char buf[];
 };
@@ -97,26 +85,6 @@ struct symdef {
 	struct dso *dso;
 };
 
-enum {
-	REL_ERR,
-	REL_SYMBOLIC,
-	REL_GOT,
-	REL_PLT,
-	REL_RELATIVE,
-	REL_OFFSET,
-	REL_OFFSET32,
-	REL_COPY,
-	REL_SYM_OR_REL,
-	REL_TLS, /* everything past here is TLS */
-	REL_DTPMOD,
-	REL_DTPOFF,
-	REL_TPOFF,
-	REL_TPOFF_NEG,
-	REL_TLSDESC,
-};
-
-#include "reloc.h"
-
 int __init_tp(void *);
 void __init_libc(char **, char *);
 
@@ -129,7 +97,8 @@ static struct builtin_tls {
 } builtin_tls[1];
 #define MIN_TLS_ALIGN offsetof(struct builtin_tls, pt)
 
-static struct dso *head, *tail, *ldso, *fini_head;
+static struct dso ldso;
+static struct dso *head, *tail, *fini_head;
 static char *env_path, *sys_path;
 static unsigned long long gencnt;
 static int runtime;
@@ -145,14 +114,19 @@ static pthread_mutex_t init_fini_lock = { ._m_type = PTHREAD_MUTEX_RECURSIVE };
 
 struct debug *_dl_debug_addr = &debug;
 
-#define AUX_CNT 38
-#define DYN_CNT 34
+static int dl_strcmp(const char *l, const char *r)
+{
+	for (; *l==*r && *l; l++, r++);
+	return *(unsigned char *)l - *(unsigned char *)r;
+}
+#define strcmp(l,r) dl_strcmp(l,r)
 
 static void decode_vec(size_t *v, size_t *a, size_t cnt)
 {
-	memset(a, 0, cnt*sizeof(size_t));
-	for (; v[0]; v+=2) if (v[0]<cnt) {
-		a[0] |= 1ULL<<v[0];
+	size_t i;
+	for (i=0; i<cnt; i++) a[i] = 0;
+	for (; v[0]; v+=2) if (v[0]-1<cnt-1) {
+		a[0] |= 1UL<<v[0];
 		a[v[0]] = v[1];
 	}
 }
@@ -276,8 +250,6 @@ static struct symdef find_sym(struct dso *dso, const char *s, int need_def)
 	return def;
 }
 
-#define NO_INLINE_ADDEND (1<<REL_COPY | 1<<REL_GOT | 1<<REL_PLT)
-
 ptrdiff_t __tlsdesc_static(), __tlsdesc_dynamic();
 
 static void do_relocs(struct dso *dso, size_t *rel, size_t rel_size, size_t stride)
@@ -288,7 +260,7 @@ static void do_relocs(struct dso *dso, size_t *rel, size_t rel_size, size_t stri
 	Sym *sym;
 	const char *name;
 	void *ctx;
-	int astype, type;
+	int type;
 	int sym_index;
 	struct symdef def;
 	size_t *reloc_addr;
@@ -297,14 +269,8 @@ static void do_relocs(struct dso *dso, size_t *rel, size_t rel_size, size_t stri
 	size_t addend;
 
 	for (; rel_size; rel+=stride, rel_size-=stride*sizeof(size_t)) {
-		astype = R_TYPE(rel[1]);
-		if (!astype) continue;
-		type = remap_rel(astype);
-		if (!type) {
-			error("Error relocating %s: unsupported relocation type %d",
-				dso->name, astype);
-			continue;
-		}
+		if (dso->rel_early_relative && IS_RELATIVE(rel[1])) continue;
+		type = R_TYPE(rel[1]);
 		sym_index = R_SYM(rel[1]);
 		reloc_addr = (void *)(base + rel[0]);
 		if (sym_index) {
@@ -324,14 +290,19 @@ static void do_relocs(struct dso *dso, size_t *rel, size_t rel_size, size_t stri
 			def.dso = dso;
 		}
 
+		int gotplt = (type == REL_GOT || type == REL_PLT);
+		if (dso->rel_update_got && !gotplt) continue;
+
 		addend = stride>2 ? rel[2]
-			: (1<<type & NO_INLINE_ADDEND) ? 0
+			: gotplt || type==REL_COPY ? 0
 			: *reloc_addr;
 
 		sym_val = def.sym ? (size_t)def.dso->base+def.sym->st_value : 0;
 		tls_val = def.sym ? def.sym->st_value : 0;
 
 		switch(type) {
+		case REL_NONE:
+			break;
 		case REL_OFFSET:
 			addend -= (size_t)reloc_addr;
 		case REL_SYMBOLIC:
@@ -395,6 +366,10 @@ static void do_relocs(struct dso *dso, size_t *rel, size_t rel_size, size_t stri
 #endif
 			}
 			break;
+		default:
+			error("Error relocating %s: unsupported relocation type %d",
+				dso->name, type);
+			continue;
 		}
 	}
 }
@@ -711,22 +686,22 @@ static struct dso *load_library(const char *name, struct dso *needed_by)
 					if (!(reported & mask)) {
 						reported |= mask;
 						dprintf(1, "\t%s => %s (%p)\n",
-							name, ldso->name,
-							ldso->base);
+							name, ldso.name,
+							ldso.base);
 					}
 				}
 				is_self = 1;
 			}
 		}
 	}
-	if (!strcmp(name, ldso->name)) is_self = 1;
+	if (!strcmp(name, ldso.name)) is_self = 1;
 	if (is_self) {
-		if (!ldso->prev) {
-			tail->next = ldso;
-			ldso->prev = tail;
-			tail = ldso->next ? ldso->next : ldso;
+		if (!ldso.prev) {
+			tail->next = &ldso;
+			ldso.prev = tail;
+			tail = ldso.next ? ldso.next : &ldso;
 		}
-		return ldso;
+		return &ldso;
 	}
 	if (strchr(name, '/')) {
 		pathname = name;
@@ -752,13 +727,13 @@ static struct dso *load_library(const char *name, struct dso *needed_by)
 			if (!sys_path) {
 				char *prefix = 0;
 				size_t prefix_len;
-				if (ldso->name[0]=='/') {
+				if (ldso.name[0]=='/') {
 					char *s, *t, *z;
-					for (s=t=z=ldso->name; *s; s++)
+					for (s=t=z=ldso.name; *s; s++)
 						if (*s=='/') z=t, t=s;
-					prefix_len = z-ldso->name;
+					prefix_len = z-ldso.name;
 					if (prefix_len < PATH_MAX)
-						prefix = ldso->name;
+						prefix = ldso.name;
 				}
 				if (!prefix) {
 					prefix = "";
@@ -910,21 +885,40 @@ static void make_global(struct dso *p)
 	for (; p; p=p->next) p->global = 1;
 }
 
+static void do_mips_relocs(struct dso *p, size_t *got)
+{
+	size_t i, j, rel[2];
+	unsigned char *base = p->base;
+	i=0; search_vec(p->dynv, &i, DT_MIPS_LOCAL_GOTNO);
+	if (p->rel_early_relative) {
+		got += i;
+	} else {
+		while (i--) *got++ += (size_t)base;
+	}
+	j=0; search_vec(p->dynv, &j, DT_MIPS_GOTSYM);
+	i=0; search_vec(p->dynv, &i, DT_MIPS_SYMTABNO);
+	Sym *sym = p->syms + j;
+	rel[0] = (unsigned char *)got - base;
+	for (i-=j; i; i--, sym++, rel[0]+=sizeof(size_t)) {
+		rel[1] = sym-p->syms << 8 | R_MIPS_JUMP_SLOT;
+		do_relocs(p, rel, sizeof rel, 2);
+	}
+}
+
 static void reloc_all(struct dso *p)
 {
 	size_t dyn[DYN_CNT] = {0};
 	for (; p; p=p->next) {
 		if (p->relocated) continue;
 		decode_vec(p->dynv, dyn, DYN_CNT);
-#ifdef NEED_ARCH_RELOCS
-		do_arch_relocs(p, head);
-#endif
+		if (NEED_MIPS_GOT_RELOCS)
+			do_mips_relocs(p, (void *)(p->base+dyn[DT_PLTGOT]));
 		do_relocs(p, (void *)(p->base+dyn[DT_JMPREL]), dyn[DT_PLTRELSZ],
 			2+(dyn[DT_PLTREL]==DT_RELA));
 		do_relocs(p, (void *)(p->base+dyn[DT_REL]), dyn[DT_RELSZ], 2);
 		do_relocs(p, (void *)(p->base+dyn[DT_RELA]), dyn[DT_RELASZ], 3);
 
-		if (p->relro_start != p->relro_end &&
+		if (head != &ldso && p->relro_start != p->relro_end &&
 		    mprotect(p->base+p->relro_start, p->relro_end-p->relro_start, PROT_READ) < 0) {
 			error("Error relocating %s: RELRO protection failed: %m",
 				p->name);
@@ -1121,19 +1115,52 @@ static void update_tls_size()
 	tls_align);
 }
 
-void *__dynlink(int argc, char **argv)
+/* Stage 1 of the dynamic linker is defined in dlstart.c. It calls the
+ * following stage 2 and stage 3 functions via primitive symbolic lookup
+ * since it does not have access to their addresses to begin with. */
+
+/* Stage 2 of the dynamic linker is called after relative relocations 
+ * have been processed. It can make function calls to static functions
+ * and access string literals and static data, but cannot use extern
+ * symbols. Its job is to perform symbolic relocations on the dynamic
+ * linker itself, but some of the relocations performed may need to be
+ * replaced later due to copy relocations in the main program. */
+
+void __dls2(unsigned char *base)
 {
-	size_t aux[AUX_CNT] = {0};
+	Ehdr *ehdr = (void *)base;
+	ldso.base = base;
+	ldso.name = ldso.shortname = "libc.so";
+	ldso.global = 1;
+	ldso.phnum = ehdr->e_phnum;
+	ldso.phdr = (void *)(base + ehdr->e_phoff);
+	ldso.phentsize = ehdr->e_phentsize;
+	ldso.rel_early_relative = 1;
+	kernel_mapped_dso(&ldso);
+	decode_dyn(&ldso);
+
+	head = &ldso;
+	reloc_all(&ldso);
+
+	ldso.relocated = 0;
+	ldso.rel_update_got = 1;
+}
+
+/* Stage 3 of the dynamic linker is called with the dynamic linker/libc
+ * fully functional. Its job is to load (if not already loaded) and
+ * process dependencies and relocations for the main application and
+ * transfer control to its entry point. */
+
+_Noreturn void __dls3(size_t *sp)
+{
+	static struct dso app, vdso;
+	size_t aux[AUX_CNT] = {0}, *auxv;
 	size_t i;
-	Phdr *phdr;
-	Ehdr *ehdr;
-	static struct dso builtin_dsos[3];
-	struct dso *const app = builtin_dsos+0;
-	struct dso *const lib = builtin_dsos+1;
-	struct dso *const vdso = builtin_dsos+2;
 	char *env_preload=0;
 	size_t vdso_base;
-	size_t *auxv;
+	int argc = *sp;
+	char **argv = (void *)(sp+1);
+	char **argv_orig = argv;
 	char **envp = argv+argc+1;
 	void *initial_tls;
 
@@ -1157,60 +1184,42 @@ void *__dynlink(int argc, char **argv)
 	libc.page_size = aux[AT_PAGESZ];
 	libc.auxv = auxv;
 
-	/* If the dynamic linker was invoked as a program itself, AT_BASE
-	 * will not be set. In that case, we assume the base address is
-	 * the start of the page containing the PHDRs; I don't know any
-	 * better approach... */
-	if (!aux[AT_BASE]) {
-		aux[AT_BASE] = aux[AT_PHDR] & -PAGE_SIZE;
-		aux[AT_PHDR] = aux[AT_PHENT] = aux[AT_PHNUM] = 0;
-	}
-
-	/* The dynamic linker load address is passed by the kernel
-	 * in the AUX vector, so this is easy. */
-	lib->base = (void *)aux[AT_BASE];
-	lib->name = lib->shortname = "libc.so";
-	lib->global = 1;
-	ehdr = (void *)lib->base;
-	lib->phnum = ehdr->e_phnum;
-	lib->phdr = (void *)(aux[AT_BASE]+ehdr->e_phoff);
-	lib->phentsize = ehdr->e_phentsize;
-	kernel_mapped_dso(lib);
-	decode_dyn(lib);
-
-	if (aux[AT_PHDR]) {
+	/* If the main program was already loaded by the kernel,
+	 * AT_PHDR will point to some location other than the dynamic
+	 * linker's program headers. */
+	if (aux[AT_PHDR] != (size_t)ldso.phdr) {
 		size_t interp_off = 0;
 		size_t tls_image = 0;
 		/* Find load address of the main program, via AT_PHDR vs PT_PHDR. */
-		app->phdr = phdr = (void *)aux[AT_PHDR];
-		app->phnum = aux[AT_PHNUM];
-		app->phentsize = aux[AT_PHENT];
+		Phdr *phdr = app.phdr = (void *)aux[AT_PHDR];
+		app.phnum = aux[AT_PHNUM];
+		app.phentsize = aux[AT_PHENT];
 		for (i=aux[AT_PHNUM]; i; i--, phdr=(void *)((char *)phdr + aux[AT_PHENT])) {
 			if (phdr->p_type == PT_PHDR)
-				app->base = (void *)(aux[AT_PHDR] - phdr->p_vaddr);
+				app.base = (void *)(aux[AT_PHDR] - phdr->p_vaddr);
 			else if (phdr->p_type == PT_INTERP)
 				interp_off = (size_t)phdr->p_vaddr;
 			else if (phdr->p_type == PT_TLS) {
 				tls_image = phdr->p_vaddr;
-				app->tls_len = phdr->p_filesz;
-				app->tls_size = phdr->p_memsz;
-				app->tls_align = phdr->p_align;
+				app.tls_len = phdr->p_filesz;
+				app.tls_size = phdr->p_memsz;
+				app.tls_align = phdr->p_align;
 			}
 		}
-		if (app->tls_size) app->tls_image = (char *)app->base + tls_image;
-		if (interp_off) lib->name = (char *)app->base + interp_off;
+		if (app.tls_size) app.tls_image = (char *)app.base + tls_image;
+		if (interp_off) ldso.name = (char *)app.base + interp_off;
 		if ((aux[0] & (1UL<<AT_EXECFN))
 		    && strncmp((char *)aux[AT_EXECFN], "/proc/", 6))
-			app->name = (char *)aux[AT_EXECFN];
+			app.name = (char *)aux[AT_EXECFN];
 		else
-			app->name = argv[0];
-		kernel_mapped_dso(app);
+			app.name = argv[0];
+		kernel_mapped_dso(&app);
 	} else {
 		int fd;
 		char *ldname = argv[0];
 		size_t l = strlen(ldname);
 		if (l >= 3 && !strcmp(ldname+l-3, "ldd")) ldd_mode = 1;
-		*argv++ = (void *)-1;
+		argv++;
 		while (argv[0] && argv[0][0]=='-' && argv[0][1]=='-') {
 			char *opt = argv[0]+2;
 			*argv++ = (void *)-1;
@@ -1229,8 +1238,8 @@ void *__dynlink(int argc, char **argv)
 			} else {
 				argv[0] = 0;
 			}
-			argv[-1] = (void *)-1;
 		}
+		argv[-1] = (void *)(argc - (argv-argv_orig));
 		if (!argv[0]) {
 			dprintf(2, "musl libc\n"
 				"Version %s\n"
@@ -1246,96 +1255,88 @@ void *__dynlink(int argc, char **argv)
 			_exit(1);
 		}
 		runtime = 1;
-		ehdr = (void *)map_library(fd, app);
+		Ehdr *ehdr = (void *)map_library(fd, &app);
 		if (!ehdr) {
 			dprintf(2, "%s: %s: Not a valid dynamic program\n", ldname, argv[0]);
 			_exit(1);
 		}
 		runtime = 0;
 		close(fd);
-		lib->name = ldname;
-		app->name = argv[0];
-		aux[AT_ENTRY] = (size_t)app->base + ehdr->e_entry;
+		ldso.name = ldname;
+		app.name = argv[0];
+		aux[AT_ENTRY] = (size_t)app.base + ehdr->e_entry;
 		/* Find the name that would have been used for the dynamic
 		 * linker had ldd not taken its place. */
 		if (ldd_mode) {
-			for (i=0; i<app->phnum; i++) {
-				if (app->phdr[i].p_type == PT_INTERP)
-					lib->name = (void *)(app->base
-						+ app->phdr[i].p_vaddr);
+			for (i=0; i<app.phnum; i++) {
+				if (app.phdr[i].p_type == PT_INTERP)
+					ldso.name = (void *)(app.base
+						+ app.phdr[i].p_vaddr);
 			}
-			dprintf(1, "\t%s (%p)\n", lib->name, lib->base);
+			dprintf(1, "\t%s (%p)\n", ldso.name, ldso.base);
 		}
 	}
-	if (app->tls_size) {
-		app->tls_id = tls_cnt = 1;
+	if (app.tls_size) {
+		app.tls_id = tls_cnt = 1;
 #ifdef TLS_ABOVE_TP
-		app->tls_offset = 0;
-		tls_offset = app->tls_size
-			+ ( -((uintptr_t)app->tls_image + app->tls_size)
-			& (app->tls_align-1) );
+		app.tls_offset = 0;
+		tls_offset = app.tls_size
+			+ ( -((uintptr_t)app.tls_image + app.tls_size)
+			& (app.tls_align-1) );
 #else
-		tls_offset = app->tls_offset = app->tls_size
-			+ ( -((uintptr_t)app->tls_image + app->tls_size)
-			& (app->tls_align-1) );
+		tls_offset = app.tls_offset = app.tls_size
+			+ ( -((uintptr_t)app.tls_image + app.tls_size)
+			& (app.tls_align-1) );
 #endif
-		tls_align = MAXP2(tls_align, app->tls_align);
+		tls_align = MAXP2(tls_align, app.tls_align);
 	}
-	app->global = 1;
-	decode_dyn(app);
+	app.global = 1;
+	decode_dyn(&app);
 
 	/* Attach to vdso, if provided by the kernel */
 	if (search_vec(auxv, &vdso_base, AT_SYSINFO_EHDR)) {
-		ehdr = (void *)vdso_base;
-		vdso->phdr = phdr = (void *)(vdso_base + ehdr->e_phoff);
-		vdso->phnum = ehdr->e_phnum;
-		vdso->phentsize = ehdr->e_phentsize;
+		Ehdr *ehdr = (void *)vdso_base;
+		Phdr *phdr = vdso.phdr = (void *)(vdso_base + ehdr->e_phoff);
+		vdso.phnum = ehdr->e_phnum;
+		vdso.phentsize = ehdr->e_phentsize;
 		for (i=ehdr->e_phnum; i; i--, phdr=(void *)((char *)phdr + ehdr->e_phentsize)) {
 			if (phdr->p_type == PT_DYNAMIC)
-				vdso->dynv = (void *)(vdso_base + phdr->p_offset);
+				vdso.dynv = (void *)(vdso_base + phdr->p_offset);
 			if (phdr->p_type == PT_LOAD)
-				vdso->base = (void *)(vdso_base - phdr->p_vaddr + phdr->p_offset);
+				vdso.base = (void *)(vdso_base - phdr->p_vaddr + phdr->p_offset);
 		}
-		vdso->name = "";
-		vdso->shortname = "linux-gate.so.1";
-		vdso->global = 1;
-		decode_dyn(vdso);
-		vdso->prev = lib;
-		lib->next = vdso;
+		vdso.name = "";
+		vdso.shortname = "linux-gate.so.1";
+		vdso.global = 1;
+		vdso.relocated = 1;
+		decode_dyn(&vdso);
+		vdso.prev = &ldso;
+		ldso.next = &vdso;
 	}
 
-	/* Initial dso chain consists only of the app. We temporarily
-	 * append the dynamic linker/libc so we can relocate it, then
-	 * restore the initial chain in preparation for loading third
-	 * party libraries (preload/needed). */
-	head = tail = app;
-	ldso = lib;
-	app->next = lib;
-	reloc_all(lib);
-	app->next = 0;
-
-	/* PAST THIS POINT, ALL LIBC INTERFACES ARE FULLY USABLE. */
+	/* Initial dso chain consists only of the app. */
+	head = tail = &app;
 
 	/* Donate unused parts of app and library mapping to malloc */
-	reclaim_gaps(app);
-	reclaim_gaps(lib);
+	reclaim_gaps(&app);
+	reclaim_gaps(&ldso);
 
 	/* Load preload/needed libraries, add their symbols to the global
-	 * namespace, and perform all remaining relocations. The main
-	 * program must be relocated LAST since it may contain copy
-	 * relocations which depend on libraries' relocations. */
+	 * namespace, and perform all remaining relocations. */
 	if (env_preload) load_preload(env_preload);
-	load_deps(app);
-	make_global(app);
+	load_deps(&app);
+	make_global(&app);
 
 #ifndef DYNAMIC_IS_RO
-	for (i=0; app->dynv[i]; i+=2)
-		if (app->dynv[i]==DT_DEBUG)
-			app->dynv[i+1] = (size_t)&debug;
+	for (i=0; app.dynv[i]; i+=2)
+		if (app.dynv[i]==DT_DEBUG)
+			app.dynv[i+1] = (size_t)&debug;
 #endif
 
-	reloc_all(app->next);
-	reloc_all(app);
+	/* The main program must be relocated LAST since it may contin
+	 * copy relocations which depend on libraries' relocations. */
+	reloc_all(app.next);
+	reloc_all(&app);
 
 	update_tls_size();
 	if (libc.tls_size > sizeof builtin_tls) {
@@ -1359,14 +1360,13 @@ void *__dynlink(int argc, char **argv)
 
 	/* Switch to runtime mode: any further failures in the dynamic
 	 * linker are a reportable failure rather than a fatal startup
-	 * error. If the dynamic loader (dlopen) will not be used, free
-	 * all memory used by the dynamic linker. */
+	 * error. */
 	runtime = 1;
 
 	debug.ver = 1;
 	debug.bp = _dl_debug_state;
 	debug.head = head;
-	debug.base = lib->base;
+	debug.base = ldso.base;
 	debug.state = 0;
 	_dl_debug_state();
 
@@ -1375,7 +1375,8 @@ void *__dynlink(int argc, char **argv)
 	errno = 0;
 	do_init_fini(tail);
 
-	return (void *)aux[AT_ENTRY];
+	CRTJMP((void *)aux[AT_ENTRY], argv-1);
+	for(;;);
 }
 
 void *dlopen(const char *file, int mode)

src/ldso/i386/start.s

@@ -1,22 +0,0 @@
-.text
-.global _dlstart
-_dlstart:
-	xor %ebp,%ebp
-	pop %edi
-	mov %esp,%esi
-	and $-16,%esp
-	push %ebp
-	push %ebp
-	push %esi
-	push %edi
-	call __dynlink
-	mov %esi,%esp
-1:	dec %edi
-	pop %esi
-	cmp $-1,%esi
-	jz 1b
-	inc %edi
-	push %esi
-	push %edi
-	xor %edx,%edx
-	jmp *%eax

src/ldso/microblaze/start.s

@@ -1,28 +0,0 @@
-# FIXME: clearing argv entries
-.global _dlstart
-_dlstart:
-	add     r19, r0, r0
-
-	lw      r5, r0, r1
-	addi    r6, r1, 4
-	mfs     r7, rpc
-	addi    r7, r7, _GLOBAL_OFFSET_TABLE_+8
-	addi    r7, r7, _DYNAMIC@GOTOFF
-	brlid   r15, __reloc_self@PLT
-	addik   r1, r1, -16
-
-	lwi     r5, r1, 16
-	brlid   r15, __dynlink@PLT
-	addi    r6, r1, 20
-	addik   r1, r1, 16
-
-	lwi     r4, r1, 0
-1:	lwi     r5, r1, 4
-	addi    r5, r5, 1
-	bnei    r5, 1f
-	addi    r4, r4, -1
-	addi    r1, r1, 4
-	bri     1b
-1:	swi     r4, r1, 0
-	add     r5, r0, r0
-	bra     r3

src/ldso/mips/start.s

@@ -1,46 +0,0 @@
-.hidden _DYNAMIC
-.hidden __reloc_self
-.set noreorder
-.set nomacro
-.global _dlstart
-.type _dlstart,@function
-_dlstart:
-	move $fp, $0
-
-	bgezal $0, 1f
-	nop
-2:	.gpword 2b
-	.gpword _DYNAMIC
-	.gpword __reloc_self
-1:	lw $gp, 0($ra)
-	subu $gp, $ra, $gp
-
-	lw $4, 0($sp)
-	addiu $5, $sp, 4
-	lw $6, 4($ra)
-	addu $6, $6, $gp
-	addiu $7, $gp, -0x7ff0
-	subu $sp, $sp, 16
-	lw $25, 8($ra)
-	add $25, $25, $gp
-	jalr $25
-	nop
-
-	lw $25, %call16(__dynlink)($gp)
-	lw $4, 16($sp)
-	addiu $5, $sp, 20
-	jalr $25
-	nop
-
-	add $sp, $sp, 16
-	li $6, -1
-	lw $4, ($sp)
-1:	lw $5, 4($sp)
-	bne $5, $6, 2f
-	nop
-	addu $sp, $sp, 4
-	addu $4, $4, -1
-	b 1b
-	nop
-2:	sw $4, ($sp)
-	jr $2

src/ldso/or1k/start.s

@@ -1,34 +0,0 @@
-.global _dlstart
-_dlstart:
-	l.jal	1f
-	 l.nop
-1:	l.movhi	r5, gotpchi(_GLOBAL_OFFSET_TABLE_+0)
-	l.ori	r5, r5, gotpclo(_GLOBAL_OFFSET_TABLE_+4)
-	l.add	r5, r5, r9
-	l.movhi	r3, gotoffhi(_DYNAMIC)
-	l.ori	r3, r3, gotofflo(_DYNAMIC)
-	l.add	r5, r5, r3
-
-	l.lwz	r3, 0(r1)
-	l.addi	r4, r1, 4
-	l.jal	plt(__reloc_self)
-	 l.addi	r1, r1, -16
-
-	l.lwz	r3, 16(r1)
-	l.jal	plt(__dynlink)
-	 l.addi	r4, r1, 20
-	l.addi	r1, r1, 16
-
-	l.lwz	r4, 0(r1)
-1:	l.addi	r4, r4, -1
-	l.lwz	r5, 4(r1)
-	l.sfeqi	r5, -1
-	l.bf	1b
-	 l.addi	r1, r1, 4
-
-	l.addi	r4, r4, 1
-	l.addi	r1, r1, -4
-	l.sw	0(r1), r4
-
-	l.jr	r11
-	 l.ori	r3, r0, 0

src/ldso/powerpc/start.s

@@ -1,29 +0,0 @@
-	.global _dlstart
-	.type   _dlstart,@function
-_dlstart:
-	bl      1f
-2:	.long   _DYNAMIC-2b
-1:	mflr    5
-	lwz     0, 0(5)
-	add     5, 0, 5
-	lwz     3, 0(1)
-	addi    4, 1, 4
-	addi    1, 1, -16
-	bl      __reloc_self
-
-	lwz     3, 16(1)
-	addi    4, 1, 20
-	bl      __dynlink
-	addi    1, 1, 16
-
-	lwz     4, 0(1)
-1:	addi    4, 4, -1
-	lwzu    5, 4(1)
-	cmpwi   5, -1
-	beq-    1b
-	addi    4, 4, 1
-	stwu    4, -4(1)
-
-	mtlr    3
-	li      3, 0
-	blr

src/ldso/sh/start.s

@@ -1,26 +0,0 @@
-.text
-.global _dlstart
-.type   _dlstart, @function
-_dlstart:
-	mov.l  @r15, r4
-	mov    r15, r5
-	mov.l  L1, r0
-	bsrf   r0
-	 add   #4, r5
-
-2:	mov    r0, r2
-	mov.l  @r15+, r1
-1:	mov.l  @r15+, r0
-	cmp/eq #-1, r0
-	bt/s   1b
-	 add   #-1, r1
-
-	add    #1, r1
-	mov.l  r0, @-r15
-	mov.l  r1, @-r15
-	mov    #0, r4
-	jmp    @r2
-	 nop
-
-.align 2
-L1:	.long __dynlink@PLT-(2b-.)

src/ldso/start.c

@@ -1,8 +0,0 @@
-#include <stdlib.h>
-
-/* stub for archs that lack dynamic linker support */
-
-void _dlstart()
-{
-	_Exit(1);
-}

src/ldso/x32/start.s

@@ -1,24 +0,0 @@
-.text
-.global _dlstart
-_dlstart:
-	mov (%rsp),%rdi  /* move argc into 1st argument slot */
-	lea 4(%rsp),%rsi /* move argv into 2nd argument slot */
-	call __dynlink
-	/* in case the dynlinker was called directly, it sets the "consumed"
-	   argv values to -1. so we must loop over the array as long as -1
-	   is in the top argv slot, decrement argc, and then set the stackpointer
-	   to the new argc as well as argc's new value.
-	   as the x32 abi has longs in the argv array, we cannot use push/pop.*/
-	movl (%rsp),%edi /* copy argc into edi */
-	xor %rdx,%rdx /* we use rdx as an offset to the current argv member */
-1:	dec %edi
-	addl $4, %edx
-	movl (%rsp, %rdx), %esi
-	cmp $-1,%esi
-	jz 1b
-	inc %edi
-	subl $4, %edx
-	lea (%rsp, %rdx), %rsp /* set rsp to new argv[-1] */
-	movl %edi, (%rsp)      /* write new argc there */
-	xor %edx,%edx
-	jmp *%rax

src/ldso/x86_64/start.s

@@ -1,16 +0,0 @@
-.text
-.global _dlstart
-_dlstart:
-	mov (%rsp),%rdi
-	lea 8(%rsp),%rsi
-	call __dynlink
-	pop %rdi
-1:	dec %edi
-	pop %rsi
-	cmp $-1,%rsi
-	jz 1b
-	inc %edi
-	push %rsi
-	push %rdi
-	xor %edx,%edx
-	jmp *%rax