dynamic linking support for powerpc

incomplete but at least partly working. requires all files to be
compiled in the new "secure" plt model, not the old one that put plt
code in the data segment. TLS is untested but may work. invoking the
dynamic linker explicitly to load a program does not yet handle argv
correctly.

arch/powerpc/reloc.h

@@ -16,21 +16,40 @@ static inline void do_single_reloc(
 	switch(type) {
 	case R_PPC_GLOB_DAT:
 	case R_PPC_JMP_SLOT:
-		*reloc_addr = sym_val;
-		break;
-	case R_PPC_REL32:
-		if (sym_val) *reloc_addr += sym_val;
-		else *reloc_addr += (size_t)base_addr;
+	case R_PPC_ADDR32:
+		*reloc_addr = sym_val + addend;
 		break;
 	case R_PPC_COPY:
 		memcpy(reloc_addr, (void *)sym_val, sym_size);
 		break;
 	case R_PPC_RELATIVE:
-		*reloc_addr += (size_t)base_addr;
+		*reloc_addr = (size_t)base_addr + addend;
 		break;
-	//case R_PPC64_DTPMOD64:  //R_X86_64_DTPMOD64:
-	case R_PPC_DTPMOD32:  //R_386_TLS_DTPMOD32:
+	case R_PPC_DTPMOD32:
 		*reloc_addr = def.dso ? def.dso->tls_id : self->tls_id;
 		break;
+	case R_PPC_DTPREL32:
+		*reloc_addr = def.sym->st_value + addend;
+		break;
+	case R_PPC_TPREL32:
+		*reloc_addr += def.sym
+			? def.sym->st_value + def.dso->tls_offset - 0x7000
+			: self->tls_offset - 0x7000;
+		break;
 	}
 }
+
+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] & -4096);
+	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];
+}

src/ldso/powerpc/start.s

@@ -1,22 +1,21 @@
-# FIXME : does not work, the small data array needs to be relocated.
-# see elfspec_ppc.pdf, page 76-84
 	.global _start
 	.type   _start,@function
 _start:
-	mr      9, 1                  # Save the original stack pointer.
-	clrrwi  1, 1, 4               # Align the stack to 16 bytes.
-	lis     13, _SDA_BASE_@ha      # r13 points to the small data area.
-	addi    13, 13, _SDA_BASE_@l
-	li      0, 0                   # Zero the frame pointer.
-	lwz     3, 0(9)               # and argc...
-	addi    4, 9, 4               # and argv ...
-	mtlr    0                      # Clear the link register.
-	# Go to the musl dynamic linker entry point.
+	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
-	cmpi    4, 0, 3, 1            # Check for a 1.
-	bne     4, .                   # Stay here
-	mtlr    3                      # Set the link address...
+	addi    1, 1, 16
+
+	mtlr    3
 	li      3, 0
-	blr                             # and go.
-	.end    _start
-	.size   _start, .-_start
+	blr