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arm-link.c
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#ifdef TARGET_DEFS_ONLY
#define EM_TCC_TARGET EM_ARM
/* relocation type for 32 bit data relocation */
#define R_DATA_32 R_ARM_ABS32
#define R_DATA_PTR R_ARM_ABS32
#define R_JMP_SLOT R_ARM_JUMP_SLOT
#define R_GLOB_DAT R_ARM_GLOB_DAT
#define R_COPY R_ARM_COPY
#define R_RELATIVE R_ARM_RELATIVE
#define R_NUM R_ARM_NUM
#define ELF_START_ADDR 0x00010000
#define ELF_PAGE_SIZE 0x10000
#define PCRELATIVE_DLLPLT 1
#define RELOCATE_DLLPLT 1
enum float_abi {
ARM_SOFTFP_FLOAT,
ARM_HARD_FLOAT,
};
#else /* !TARGET_DEFS_ONLY */
#include "tcc.h"
#ifdef NEED_RELOC_TYPE
/* Returns 1 for a code relocation, 0 for a data relocation. For unknown
relocations, returns -1. */
ST_FUNC int code_reloc (int reloc_type)
{
switch (reloc_type) {
case R_ARM_MOVT_ABS:
case R_ARM_MOVW_ABS_NC:
case R_ARM_THM_MOVT_ABS:
case R_ARM_THM_MOVW_ABS_NC:
case R_ARM_ABS32:
case R_ARM_REL32:
case R_ARM_GOTPC:
case R_ARM_GOTOFF:
case R_ARM_GOT32:
case R_ARM_GOT_PREL:
case R_ARM_COPY:
case R_ARM_GLOB_DAT:
case R_ARM_NONE:
case R_ARM_TARGET1:
case R_ARM_MOVT_PREL:
case R_ARM_MOVW_PREL_NC:
return 0;
case R_ARM_PC24:
case R_ARM_CALL:
case R_ARM_JUMP24:
case R_ARM_PLT32:
case R_ARM_THM_PC22:
case R_ARM_THM_JUMP24:
case R_ARM_PREL31:
case R_ARM_V4BX:
case R_ARM_JUMP_SLOT:
return 1;
}
return -1;
}
/* Returns an enumerator to describe whether and when the relocation needs a
GOT and/or PLT entry to be created. See tcc.h for a description of the
different values. */
ST_FUNC int gotplt_entry_type (int reloc_type)
{
switch (reloc_type) {
case R_ARM_NONE:
case R_ARM_COPY:
case R_ARM_GLOB_DAT:
case R_ARM_JUMP_SLOT:
return NO_GOTPLT_ENTRY;
case R_ARM_PC24:
case R_ARM_CALL:
case R_ARM_JUMP24:
case R_ARM_PLT32:
case R_ARM_THM_PC22:
case R_ARM_THM_JUMP24:
case R_ARM_MOVT_ABS:
case R_ARM_MOVW_ABS_NC:
case R_ARM_THM_MOVT_ABS:
case R_ARM_THM_MOVW_ABS_NC:
case R_ARM_PREL31:
case R_ARM_ABS32:
case R_ARM_REL32:
case R_ARM_V4BX:
case R_ARM_TARGET1:
case R_ARM_MOVT_PREL:
case R_ARM_MOVW_PREL_NC:
return AUTO_GOTPLT_ENTRY;
case R_ARM_GOTPC:
case R_ARM_GOTOFF:
return BUILD_GOT_ONLY;
case R_ARM_GOT32:
case R_ARM_GOT_PREL:
return ALWAYS_GOTPLT_ENTRY;
}
return -1;
}
#ifdef NEED_BUILD_GOT
ST_FUNC unsigned create_plt_entry(TCCState *s1, unsigned got_offset, struct sym_attr *attr)
{
Section *plt = s1->plt;
uint8_t *p;
unsigned plt_offset;
/* when building a DLL, GOT entry accesses must be done relative to
start of GOT (see x86_64 example above) */
/* empty PLT: create PLT0 entry that push address of call site and
jump to ld.so resolution routine (GOT + 8) */
if (plt->data_offset == 0) {
p = section_ptr_add(plt, 20);
write32le(p, 0xe52de004); /* push {lr} */
write32le(p+4, 0xe59fe004); /* ldr lr, [pc, #4] */
write32le(p+8, 0xe08fe00e); /* add lr, pc, lr */
write32le(p+12, 0xe5bef008); /* ldr pc, [lr, #8]! */
/* p+16 is set in relocate_plt */
}
plt_offset = plt->data_offset;
if (attr->plt_thumb_stub) {
p = section_ptr_add(plt, 4);
write32le(p, 0x4778); /* bx pc */
write32le(p+2, 0x46c0); /* nop */
}
p = section_ptr_add(plt, 16);
/* save GOT offset for relocate_plt */
write32le(p + 4, got_offset);
return plt_offset;
}
/* relocate the PLT: compute addresses and offsets in the PLT now that final
address for PLT and GOT are known (see fill_program_header) */
ST_FUNC void relocate_plt(TCCState *s1)
{
uint8_t *p, *p_end;
if (!s1->plt)
return;
p = s1->plt->data;
p_end = p + s1->plt->data_offset;
if (p < p_end) {
int x = s1->got->sh_addr - s1->plt->sh_addr - 12;
write32le(s1->plt->data + 16, x - 4);
p += 20;
while (p < p_end) {
unsigned off = x + read32le(p + 4) + (s1->plt->data - p) + 4;
if (read32le(p) == 0x46c04778) /* PLT Thumb stub present */
p += 4;
write32le(p, 0xe28fc200 | ((off >> 28) & 0xf)); // add ip, pc, #0xN0000000
write32le(p + 4, 0xe28cc600 | ((off >> 20) & 0xff)); // add ip, pc, #0xNN00000
write32le(p + 8, 0xe28cca00 | ((off >> 12) & 0xff)); // add ip, ip, #0xNN000
write32le(p + 12, 0xe5bcf000 | (off & 0xfff)); // ldr pc, [ip, #0xNNN]!
p += 16;
}
}
if (s1->plt->reloc) {
ElfW_Rel *rel;
p = s1->got->data;
for_each_elem(s1->plt->reloc, 0, rel, ElfW_Rel) {
write32le(p + rel->r_offset, s1->plt->sh_addr);
}
}
}
#endif
#endif
ST_FUNC void relocate(TCCState *s1, ElfW_Rel *rel, int type, unsigned char *ptr, addr_t addr, addr_t val)
{
ElfW(Sym) *sym;
int sym_index, esym_index;
sym_index = ELFW(R_SYM)(rel->r_info);
sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
switch(type) {
case R_ARM_PC24:
case R_ARM_CALL:
case R_ARM_JUMP24:
case R_ARM_PLT32:
{
int x, is_thumb, is_call, h, blx_avail, is_bl, th_ko;
x = (*(int *) ptr) & 0xffffff;
#ifdef DEBUG_RELOC
printf ("reloc %d: x=0x%x val=0x%x ", type, x, val);
#endif
(*(int *)ptr) &= 0xff000000;
if (x & 0x800000)
x -= 0x1000000;
x <<= 2;
blx_avail = (CONFIG_TCC_CPUVER >= 5);
is_thumb = val & 1;
is_bl = (*(unsigned *) ptr) >> 24 == 0xeb;
is_call = (type == R_ARM_CALL || (type == R_ARM_PC24 && is_bl));
x += val - addr;
#ifdef DEBUG_RELOC
printf (" newx=0x%x name=%s\n", x,
(char *) symtab_section->link->data + sym->st_name);
#endif
h = x & 2;
th_ko = (x & 3) && (!blx_avail || !is_call);
if (th_ko || x >= 0x2000000 || x < -0x2000000)
tcc_error_noabort("can't relocate value at %x,%d",addr, type);
x >>= 2;
x &= 0xffffff;
/* Only reached if blx is avail and it is a call */
if (is_thumb) {
x |= h << 24;
(*(int *)ptr) = 0xfa << 24; /* bl -> blx */
}
(*(int *) ptr) |= x;
}
return;
/* Since these relocations only concern Thumb-2 and blx instruction was
introduced before Thumb-2, we can assume blx is available and not
guard its use */
case R_ARM_THM_PC22:
case R_ARM_THM_JUMP24:
{
int x, hi, lo, s, j1, j2, i1, i2, imm10, imm11;
int to_thumb, is_call, to_plt, blx_bit = 1 << 12;
Section *plt;
/* weak reference */
if (sym->st_shndx == SHN_UNDEF &&
ELFW(ST_BIND)(sym->st_info) == STB_WEAK)
return;
/* Get initial offset */
hi = (*(uint16_t *)ptr);
lo = (*(uint16_t *)(ptr+2));
s = (hi >> 10) & 1;
j1 = (lo >> 13) & 1;
j2 = (lo >> 11) & 1;
i1 = (j1 ^ s) ^ 1;
i2 = (j2 ^ s) ^ 1;
imm10 = hi & 0x3ff;
imm11 = lo & 0x7ff;
x = (s << 24) | (i1 << 23) | (i2 << 22) |
(imm10 << 12) | (imm11 << 1);
if (x & 0x01000000)
x -= 0x02000000;
/* Relocation infos */
to_thumb = val & 1;
plt = s1->plt;
to_plt = (val >= plt->sh_addr) &&
(val < plt->sh_addr + plt->data_offset);
is_call = (type == R_ARM_THM_PC22);
if (!to_thumb && !to_plt && !is_call) {
int index;
uint8_t *p;
char *name, buf[1024];
Section *text;
name = (char *) symtab_section->link->data + sym->st_name;
text = s1->sections[sym->st_shndx];
/* Modify reloc to target a thumb stub to switch to ARM */
snprintf(buf, sizeof(buf), "%s_from_thumb", name);
index = put_elf_sym(symtab_section,
text->data_offset + 1,
sym->st_size, sym->st_info, 0,
sym->st_shndx, buf);
to_thumb = 1;
val = text->data_offset + 1;
rel->r_info = ELFW(R_INFO)(index, type);
/* Create a thumb stub function to switch to ARM mode */
put_elf_reloc(symtab_section, text,
text->data_offset + 4, R_ARM_JUMP24,
sym_index);
p = section_ptr_add(text, 8);
write32le(p, 0x4778); /* bx pc */
write32le(p+2, 0x46c0); /* nop */
write32le(p+4, 0xeafffffe); /* b $sym */
}
/* Compute final offset */
x += val - addr;
if (!to_thumb && is_call) {
blx_bit = 0; /* bl -> blx */
x = (x + 3) & -4; /* Compute offset from aligned PC */
}
/* Check that relocation is possible
* offset must not be out of range
* if target is to be entered in arm mode:
- bit 1 must not set
- instruction must be a call (bl) or a jump to PLT */
if (!to_thumb || x >= 0x1000000 || x < -0x1000000)
if (to_thumb || (val & 2) || (!is_call && !to_plt))
tcc_error_noabort("can't relocate value at %x,%d",addr, type);
/* Compute and store final offset */
s = (x >> 24) & 1;
i1 = (x >> 23) & 1;
i2 = (x >> 22) & 1;
j1 = s ^ (i1 ^ 1);
j2 = s ^ (i2 ^ 1);
imm10 = (x >> 12) & 0x3ff;
imm11 = (x >> 1) & 0x7ff;
(*(uint16_t *)ptr) = (uint16_t) ((hi & 0xf800) |
(s << 10) | imm10);
(*(uint16_t *)(ptr+2)) = (uint16_t) ((lo & 0xc000) |
(j1 << 13) | blx_bit | (j2 << 11) |
imm11);
}
return;
case R_ARM_MOVT_ABS:
case R_ARM_MOVW_ABS_NC:
{
int x, imm4, imm12;
if (type == R_ARM_MOVT_ABS)
val >>= 16;
imm12 = val & 0xfff;
imm4 = (val >> 12) & 0xf;
x = (imm4 << 16) | imm12;
if (type == R_ARM_THM_MOVT_ABS)
*(int *)ptr |= x;
else
*(int *)ptr += x;
}
return;
case R_ARM_MOVT_PREL:
case R_ARM_MOVW_PREL_NC:
{
int insn = *(int *)ptr;
int addend = ((insn >> 4) & 0xf000) | (insn & 0xfff);
addend = (addend ^ 0x8000) - 0x8000;
val += addend - addr;
if (type == R_ARM_MOVT_PREL)
val >>= 16;
*(int *)ptr = (insn & 0xfff0f000) |
((val & 0xf000) << 4) | (val & 0xfff);
}
return;
case R_ARM_THM_MOVT_ABS:
case R_ARM_THM_MOVW_ABS_NC:
{
int x, i, imm4, imm3, imm8;
if (type == R_ARM_THM_MOVT_ABS)
val >>= 16;
imm8 = val & 0xff;
imm3 = (val >> 8) & 0x7;
i = (val >> 11) & 1;
imm4 = (val >> 12) & 0xf;
x = (imm3 << 28) | (imm8 << 16) | (i << 10) | imm4;
if (type == R_ARM_THM_MOVT_ABS)
*(int *)ptr |= x;
else
*(int *)ptr += x;
}
return;
case R_ARM_PREL31:
{
int x;
x = (*(int *)ptr) & 0x7fffffff;
(*(int *)ptr) &= 0x80000000;
x = (x * 2) / 2;
x += val - addr;
if((x^(x>>1))&0x40000000)
tcc_error_noabort("can't relocate value at %x,%d",addr, type);
(*(int *)ptr) |= x & 0x7fffffff;
}
return;
case R_ARM_ABS32:
case R_ARM_TARGET1:
if (s1->output_type & TCC_OUTPUT_DYN) {
esym_index = get_sym_attr(s1, sym_index, 0)->dyn_index;
qrel->r_offset = rel->r_offset;
if (esym_index) {
qrel->r_info = ELFW(R_INFO)(esym_index, R_ARM_ABS32);
qrel++;
return;
} else {
qrel->r_info = ELFW(R_INFO)(0, R_ARM_RELATIVE);
qrel++;
}
}
*(int *)ptr += val;
return;
case R_ARM_REL32:
*(int *)ptr += val - addr;
return;
case R_ARM_GOTPC:
*(int *)ptr += s1->got->sh_addr - addr;
return;
case R_ARM_GOTOFF:
*(int *)ptr += val - s1->got->sh_addr;
return;
case R_ARM_GOT32:
/* we load the got offset */
*(int *)ptr += get_sym_attr(s1, sym_index, 0)->got_offset;
return;
case R_ARM_GOT_PREL:
/* we load the pc relative got offset */
*(int *)ptr += s1->got->sh_addr +
get_sym_attr(s1, sym_index, 0)->got_offset -
addr;
return;
case R_ARM_COPY:
return;
case R_ARM_V4BX:
/* trade Thumb support for ARMv4 support */
if ((0x0ffffff0 & *(int*)ptr) == 0x012FFF10)
*(int*)ptr ^= 0xE12FFF10 ^ 0xE1A0F000; /* BX Rm -> MOV PC, Rm */
return;
case R_ARM_GLOB_DAT:
case R_ARM_JUMP_SLOT:
*(addr_t *)ptr = val;
return;
case R_ARM_NONE:
/* Nothing to do. Normally used to indicate a dependency
on a certain symbol (like for exception handling under EABI). */
return;
case R_ARM_RELATIVE:
#ifdef TCC_TARGET_PE
add32le(ptr, val - s1->pe_imagebase);
#endif
/* do nothing */
return;
default:
fprintf(stderr,"FIXME: handle reloc type %d at %x [%p] to %x\n",
type, (unsigned)addr, ptr, (unsigned)val);
return;
}
}
#endif /* !TARGET_DEFS_ONLY */