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https://github.com/frida/tinycc
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0bf262864c
i386 target does not have PC relative loads. Its ABI therefore require ebx register to points to the GOT when executing a PLT entry. This means that PLT entry cannot be used transparently, the compiler needs to expect execution of a PLT entry to be able to use one, that is a PLT entry should only be created if the relocation explicitely asks for it (eg. R_386_PLT32). This patch creates a new target macro PCRELATIVE_DLLPLT to indicate whether a target can do a PC relative load in PLT entry when building a dynamic library. Executable do not normally pose a problem because they are loaded at a fixed address and thus the absolute address of GOT can be used. Note that in such a case, if the compiler does not use a PLT aware relocation for external access then the code relocation will fall on the dynamic loader since there is no PLT entry to relocate too.
278 lines
10 KiB
C
278 lines
10 KiB
C
#ifdef TARGET_DEFS_ONLY
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#define EM_TCC_TARGET EM_ARM
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/* relocation type for 32 bit data relocation */
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#define R_DATA_32 R_ARM_ABS32
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#define R_DATA_PTR R_ARM_ABS32
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#define R_JMP_SLOT R_ARM_JUMP_SLOT
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#define R_GLOB_DAT R_ARM_GLOB_DAT
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#define R_COPY R_ARM_COPY
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#define R_NUM R_ARM_NUM
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#define ELF_START_ADDR 0x00008000
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#define ELF_PAGE_SIZE 0x1000
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#define HAVE_SECTION_RELOC
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#define PCRELATIVE_DLLPLT 1
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enum float_abi {
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ARM_SOFTFP_FLOAT,
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ARM_HARD_FLOAT,
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};
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#else /* !TARGET_DEFS_ONLY */
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#include "tcc.h"
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ST_DATA struct reloc_info relocs_info[R_NUM] = {
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INIT_RELOC_INFO (R_ARM_PC24, 1, AUTO_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_CALL, 1, AUTO_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_JUMP24, 1, AUTO_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_PLT32, 1, ALWAYS_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_THM_PC22, 1, AUTO_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_THM_JUMP24, 1, AUTO_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_MOVT_ABS, 0, AUTO_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_MOVW_ABS_NC, 0, AUTO_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_THM_MOVT_ABS, 0, AUTO_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_THM_MOVW_ABS_NC, 0, AUTO_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_PREL31, 1, AUTO_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_ABS32, 0, AUTO_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_REL32, 0, AUTO_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_GOTPC, 0, BUILD_GOT_ONLY, 0)
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INIT_RELOC_INFO (R_ARM_GOTOFF, 0, BUILD_GOT_ONLY, 0)
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INIT_RELOC_INFO (R_ARM_GOT32, 0, ALWAYS_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_COPY, 0, NO_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_V4BX, 1, AUTO_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_GLOB_DAT, 0, NO_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_JUMP_SLOT, 1, NO_GOTPLT_ENTRY, 0)
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INIT_RELOC_INFO (R_ARM_NONE, 0, NO_GOTPLT_ENTRY, 0)
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};
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void relocate_init(Section *sr) {}
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void relocate(TCCState *s1, ElfW_Rel *rel, int type, char *ptr, addr_t addr, addr_t val)
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{
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ElfW(Sym) *sym;
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int sym_index;
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sym_index = ELFW(R_SYM)(rel->r_info);
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sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
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switch(type) {
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case R_ARM_PC24:
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case R_ARM_CALL:
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case R_ARM_JUMP24:
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case R_ARM_PLT32:
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{
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int x, is_thumb, is_call, h, blx_avail, is_bl, th_ko;
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x = (*(int *) ptr) & 0xffffff;
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#ifdef DEBUG_RELOC
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printf ("reloc %d: x=0x%x val=0x%x ", type, x, val);
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#endif
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(*(int *)ptr) &= 0xff000000;
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if (x & 0x800000)
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x -= 0x1000000;
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x <<= 2;
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blx_avail = (TCC_ARM_VERSION >= 5);
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is_thumb = val & 1;
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is_bl = (*(unsigned *) ptr) >> 24 == 0xeb;
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is_call = (type == R_ARM_CALL || (type == R_ARM_PC24 && is_bl));
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x += val - addr;
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#ifdef DEBUG_RELOC
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printf (" newx=0x%x name=%s\n", x,
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(char *) symtab_section->link->data + sym->st_name);
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#endif
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h = x & 2;
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th_ko = (x & 3) && (!blx_avail || !is_call);
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if (th_ko || x >= 0x2000000 || x < -0x2000000)
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tcc_error("can't relocate value at %x,%d",addr, type);
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x >>= 2;
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x &= 0xffffff;
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/* Only reached if blx is avail and it is a call */
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if (is_thumb) {
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x |= h << 24;
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(*(int *)ptr) = 0xfa << 24; /* bl -> blx */
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}
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(*(int *) ptr) |= x;
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}
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return;
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/* Since these relocations only concern Thumb-2 and blx instruction was
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introduced before Thumb-2, we can assume blx is available and not
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guard its use */
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case R_ARM_THM_PC22:
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case R_ARM_THM_JUMP24:
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{
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int x, hi, lo, s, j1, j2, i1, i2, imm10, imm11;
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int to_thumb, is_call, to_plt, blx_bit = 1 << 12;
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Section *plt;
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/* weak reference */
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if (sym->st_shndx == SHN_UNDEF &&
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ELFW(ST_BIND)(sym->st_info) == STB_WEAK)
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return;
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/* Get initial offset */
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hi = (*(uint16_t *)ptr);
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lo = (*(uint16_t *)(ptr+2));
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s = (hi >> 10) & 1;
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j1 = (lo >> 13) & 1;
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j2 = (lo >> 11) & 1;
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i1 = (j1 ^ s) ^ 1;
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i2 = (j2 ^ s) ^ 1;
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imm10 = hi & 0x3ff;
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imm11 = lo & 0x7ff;
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x = (s << 24) | (i1 << 23) | (i2 << 22) |
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(imm10 << 12) | (imm11 << 1);
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if (x & 0x01000000)
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x -= 0x02000000;
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/* Relocation infos */
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to_thumb = val & 1;
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plt = s1->plt;
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to_plt = (val >= plt->sh_addr) &&
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(val < plt->sh_addr + plt->data_offset);
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is_call = (type == R_ARM_THM_PC22);
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if (!to_thumb && !to_plt && !is_call) {
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int index;
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uint8_t *p;
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char *name, buf[1024];
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Section *text_section;
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name = (char *) symtab_section->link->data + sym->st_name;
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text_section = s1->sections[sym->st_shndx];
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/* Modify reloc to target a thumb stub to switch to ARM */
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snprintf(buf, sizeof(buf), "%s_from_thumb", name);
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index = put_elf_sym(symtab_section,
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text_section->data_offset + 1,
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sym->st_size, sym->st_info, 0,
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sym->st_shndx, buf);
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to_thumb = 1;
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val = text_section->data_offset + 1;
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rel->r_info = ELFW(R_INFO)(index, type);
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/* Create a thumb stub function to switch to ARM mode */
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put_elf_reloc(symtab_section, text_section,
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text_section->data_offset + 4, R_ARM_JUMP24,
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sym_index);
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p = section_ptr_add(text_section, 8);
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write32le(p, 0x4778); /* bx pc */
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write32le(p+2, 0x46c0); /* nop */
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write32le(p+4, 0xeafffffe); /* b $sym */
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}
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/* Compute final offset */
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x += val - addr;
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if (!to_thumb && is_call) {
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blx_bit = 0; /* bl -> blx */
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x = (x + 3) & -4; /* Compute offset from aligned PC */
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}
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/* Check that relocation is possible
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* offset must not be out of range
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* if target is to be entered in arm mode:
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- bit 1 must not set
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- instruction must be a call (bl) or a jump to PLT */
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if (!to_thumb || x >= 0x1000000 || x < -0x1000000)
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if (to_thumb || (val & 2) || (!is_call && !to_plt))
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tcc_error("can't relocate value at %x,%d",addr, type);
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/* Compute and store final offset */
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s = (x >> 24) & 1;
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i1 = (x >> 23) & 1;
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i2 = (x >> 22) & 1;
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j1 = s ^ (i1 ^ 1);
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j2 = s ^ (i2 ^ 1);
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imm10 = (x >> 12) & 0x3ff;
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imm11 = (x >> 1) & 0x7ff;
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(*(uint16_t *)ptr) = (uint16_t) ((hi & 0xf800) |
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(s << 10) | imm10);
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(*(uint16_t *)(ptr+2)) = (uint16_t) ((lo & 0xc000) |
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(j1 << 13) | blx_bit | (j2 << 11) |
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imm11);
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}
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return;
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case R_ARM_MOVT_ABS:
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case R_ARM_MOVW_ABS_NC:
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{
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int x, imm4, imm12;
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if (type == R_ARM_MOVT_ABS)
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val >>= 16;
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imm12 = val & 0xfff;
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imm4 = (val >> 12) & 0xf;
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x = (imm4 << 16) | imm12;
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if (type == R_ARM_THM_MOVT_ABS)
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*(int *)ptr |= x;
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else
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*(int *)ptr += x;
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}
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return;
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case R_ARM_THM_MOVT_ABS:
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case R_ARM_THM_MOVW_ABS_NC:
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{
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int x, i, imm4, imm3, imm8;
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if (type == R_ARM_THM_MOVT_ABS)
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val >>= 16;
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imm8 = val & 0xff;
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imm3 = (val >> 8) & 0x7;
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i = (val >> 11) & 1;
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imm4 = (val >> 12) & 0xf;
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x = (imm3 << 28) | (imm8 << 16) | (i << 10) | imm4;
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if (type == R_ARM_THM_MOVT_ABS)
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*(int *)ptr |= x;
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else
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*(int *)ptr += x;
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}
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return;
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case R_ARM_PREL31:
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{
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int x;
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x = (*(int *)ptr) & 0x7fffffff;
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(*(int *)ptr) &= 0x80000000;
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x = (x * 2) / 2;
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x += val - addr;
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if((x^(x>>1))&0x40000000)
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tcc_error("can't relocate value at %x,%d",addr, type);
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(*(int *)ptr) |= x & 0x7fffffff;
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}
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case R_ARM_ABS32:
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*(int *)ptr += val;
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return;
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case R_ARM_REL32:
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*(int *)ptr += val - addr;
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return;
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case R_ARM_GOTPC:
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*(int *)ptr += s1->got->sh_addr - addr;
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return;
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case R_ARM_GOTOFF:
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*(int *)ptr += val - s1->got->sh_addr;
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return;
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case R_ARM_GOT32:
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/* we load the got offset */
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*(int *)ptr += s1->sym_attrs[sym_index].got_offset;
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return;
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case R_ARM_COPY:
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return;
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case R_ARM_V4BX:
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/* trade Thumb support for ARMv4 support */
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if ((0x0ffffff0 & *(int*)ptr) == 0x012FFF10)
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*(int*)ptr ^= 0xE12FFF10 ^ 0xE1A0F000; /* BX Rm -> MOV PC, Rm */
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return;
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case R_ARM_GLOB_DAT:
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case R_ARM_JUMP_SLOT:
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*(addr_t *)ptr = val;
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return;
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case R_ARM_NONE:
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/* Nothing to do. Normally used to indicate a dependency
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on a certain symbol (like for exception handling under EABI). */
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return;
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default:
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fprintf(stderr,"FIXME: handle reloc type %x at %x [%p] to %x\n",
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type, (unsigned)addr, ptr, (unsigned)val);
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return;
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}
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}
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#endif /* !TARGET_DEFS_ONLY */
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