summaryrefslogtreecommitdiff
path: root/arm-link.c
diff options
context:
space:
mode:
Diffstat (limited to 'arm-link.c')
-rw-r--r--arm-link.c398
1 files changed, 398 insertions, 0 deletions
diff --git a/arm-link.c b/arm-link.c
new file mode 100644
index 0000000..92a24eb
--- /dev/null
+++ b/arm-link.c
@@ -0,0 +1,398 @@
+#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 0x00008000
+#define ELF_PAGE_SIZE 0x1000
+
+#define PCRELATIVE_DLLPLT 1
+#define RELOCATE_DLLPLT 0
+
+enum float_abi {
+ ARM_SOFTFP_FLOAT,
+ ARM_HARD_FLOAT,
+};
+
+#else /* !TARGET_DEFS_ONLY */
+
+#include "tcc.h"
+
+/* Returns 1 for a code relocation, 0 for a data relocation. For unknown
+ relocations, returns -1. */
+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_COPY:
+ case R_ARM_GLOB_DAT:
+ case R_ARM_NONE:
+ 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;
+ }
+
+ tcc_error ("Unknown relocation type: %d", reloc_type);
+ 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. */
+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:
+ return AUTO_GOTPLT_ENTRY;
+
+ case R_ARM_GOTPC:
+ case R_ARM_GOTOFF:
+ return BUILD_GOT_ONLY;
+
+ case R_ARM_GOT32:
+ return ALWAYS_GOTPLT_ENTRY;
+ }
+
+ tcc_error ("Unknown relocation type: %d", reloc_type);
+ return -1;
+}
+
+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) */
+ if (s1->output_type == TCC_OUTPUT_DLL)
+ tcc_error("DLLs unimplemented!");
+
+ /* 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);
+ /* Jump to GOT entry where ld.so initially put address of PLT0 */
+ write32le(p, 0xe59fc004); /* ldr ip, [pc, #4] */
+ write32le(p+4, 0xe08fc00c); /* add ip, pc, ip */
+ write32le(p+8, 0xe59cf000); /* ldr pc, [ip] */
+ /* p + 12 contains offset to GOT entry once patched by relocate_plt */
+ write32le(p+12, 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 - 16);
+ p += 20;
+ while (p < p_end) {
+ if (read32le(p) == 0x46c04778) /* PLT Thumb stub present */
+ p += 4;
+ add32le(p + 12, x + s1->plt->data - p);
+ p += 16;
+ }
+ }
+}
+
+void relocate_init(Section *sr) {}
+
+void relocate(TCCState *s1, ElfW_Rel *rel, int type, unsigned char *ptr, addr_t addr, addr_t val)
+{
+ ElfW(Sym) *sym;
+ int sym_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 = (TCC_CPU_VERSION >= 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("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_section;
+
+ name = (char *) symtab_section->link->data + sym->st_name;
+ text_section = 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_section->data_offset + 1,
+ sym->st_size, sym->st_info, 0,
+ sym->st_shndx, buf);
+ to_thumb = 1;
+ val = text_section->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_section,
+ text_section->data_offset + 4, R_ARM_JUMP24,
+ sym_index);
+ p = section_ptr_add(text_section, 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("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_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("can't relocate value at %x,%d",addr, type);
+ (*(int *)ptr) |= x & 0x7fffffff;
+ }
+ case R_ARM_ABS32:
+ *(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 += s1->sym_attrs[sym_index].got_offset;
+ 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 %x at %x [%p] to %x\n",
+ type, (unsigned)addr, ptr, (unsigned)val);
+ return;
+ }
+}
+
+#endif /* !TARGET_DEFS_ONLY */
generated by cgit v1.2.3 (git 2.25.1) at 2024-06-26 23:25:57 +0000