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outmacho: make a best effort at separating SIGNED from BRANCH relocs

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For 64 bits, a BRANCH reloc is sometimes needed to fix up PIC
problems.  Make a best effort at generating BRANCH relocs just as
we make a best effort at distinguishing GOTLOAD from GOT.

This needs to be replaced with information from the assembler to
the backend.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
H. Peter Anvin 2016-02-21 20:56:19 -08:00
parent 114ba75f7b
commit a222d21138
1 changed files with 46 additions and 17 deletions
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63
output/outmacho.c
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@ -111,6 +111,7 @@ enum reltype {
RL_ABS, /* Absolute relocation */
RL_REL, /* Relative relocation */
RL_TLV, /* Thread local */
RL_BRANCH, /* Relative direct branch */
RL_SUB, /* X86_64_RELOC_SUBTRACT */
RL_GOT, /* X86_64_RELOC_GOT */
RL_GOTLOAD, /* X86_64_RELOC_GOT_LOAD */
@ -435,8 +436,14 @@ static int64_t add_reloc(struct section *sect, int32_t section,
}
break;
case RL_BRANCH:
r->type = X86_64_RELOC_BRANCH;
goto rel_or_branch;
case RL_REL:
r->type = fmt.reloc_rel;
rel_or_branch:
r->pcrel = 1;
if (section == NO_SEG) {
goto bail; /* No relocation needed */
@ -508,8 +515,9 @@ static void macho_output(int32_t secto, const void *data,
{
struct section *s;
int64_t addr, offset;
uint8_t mydata[16], *p, gotload;
uint8_t mydata[16], *p;
bool is_bss;
enum reltype reltype;
if (secto == NO_SEG) {
if (type != OUT_RESERVE)
@ -620,35 +628,56 @@ static void macho_output(int32_t secto, const void *data,
p = mydata;
offset = *(int64_t *)data;
addr = offset - size;
reltype = RL_REL;
if (section != NO_SEG && section % 2) {
nasm_error(ERR_NONFATAL, "Mach-O format does not support"
" section base references");
} else if (wrt == NO_SEG) {
/* Plain relative relocation */
addr += add_reloc(s, section, offset, RL_REL, 4);
} else if (wrt == macho_gotpcrel_sect) {
if (s->data->datalen > 1) {
/* Retrieve instruction opcode */
saa_fread(s->data, s->data->datalen-2, &gotload, 1);
} else {
gotload = 0;
if (fmt.ptrsize == 8 &&
(s->flags & S_ATTR_SOME_INSTRUCTIONS)) {
uint8_t opcode[2];
opcode[0] = opcode[1] = 0;
/* HACK: Retrieve instruction opcode */
if (likely(s->data->datalen >= 2)) {
saa_fread(s->data, s->data->datalen-2, opcode, 2);
} else if (s->data->datalen == 1) {
saa_fread(s->data, 0, opcode+1, 1);
}
if (opcode[1] == 0xe8 || opcode[1] == 0xe9 ||
(opcode[0] == 0x0f && (opcode[1] & 0xf0) == 0x80)) {
/* Direct call, jmp, or jcc */
reltype = RL_BRANCH;
}
}
if (gotload == 0x8B) {
/* Check for MOVQ Opcode -> X86_64_RELOC_GOT_LOAD */
addr += add_reloc(s, section, offset, RL_GOTLOAD, 4);
} else {
/* X86_64_RELOC_GOT */
addr += add_reloc(s, section, offset, RL_GOT, 4);
} else if (wrt == macho_gotpcrel_sect) {
reltype = RL_GOT;
if ((s->flags & S_ATTR_SOME_INSTRUCTIONS) &&
s->data->datalen >= 3) {
uint8_t gotload[3];
/* HACK: Retrieve instruction opcode */
saa_fread(s->data, s->data->datalen-3, gotload, 3);
if ((gotload[0] & 0xf8) == 0x48 &&
gotload[1] == 0x8b &&
(gotload[2] & 0307) == 0005) {
/* movq <reg>,[rel sym wrt ..gotpcrel] */
reltype = RL_GOTLOAD;
}
}
} else if (wrt == macho_tlvp_sect) {
addr += add_reloc(s, section, offset, RL_TLV, 4);
reltype = RL_TLV;
} else {
nasm_error(ERR_NONFATAL, "Mach-O format does not support"
" this use of WRT");
wrt = NO_SEG; /* we can at least _try_ to continue */
/* continue with RL_REL */
}
addr += add_reloc(s, section, offset, reltype, 4);
WRITELONG(p, addr);
sect_write(s, mydata, 4);
break;