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cpukit/libdl/arm: Support BLX relocations that require a trampoline

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BLX relocations in Thumb code expect the target to be ARM code. This
means that the trampoline must be generated in ARM mode.
This commit is contained in:
Kinsey Moore
2024-09-25 15:56:31 -05:00
committed by Kinsey Moore
parent 689e9986cd
commit c978b63c3a
1 changed files with 52 additions and 25 deletions
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77
cpukit/libdl/rtl-mdreloc-arm.c
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@@ -70,6 +70,23 @@ sign_extend31(Elf_Addr val)
return 0x7fffffff & val;
}
static void*
set_arm_veneer(void* trampoline, Elf_Addr target)
{
/*
* ARM mode:
* ldr pc, [pc, #-4]
*/
uint32_t* tramp = (uint32_t*) trampoline;
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
*tramp++ = 0xe51ff004;
#else
*tramp++ = 0xe51ff004; /* not tested */
#endif
*tramp++ = (uint32_t) target;
return tramp;
}
static void*
set_veneer(void* trampoline, Elf_Addr target)
{
@@ -79,26 +96,19 @@ set_veneer(void* trampoline, Elf_Addr target)
* Thumb mode:
* ldr.w pc, [pc]
*
* ARM mode:
* ldr pc, [pc, #-4]
*
*/
uint32_t* tramp = (uint32_t*) trampoline;
#if defined(__thumb__)
uint32_t* tramp = (uint32_t*) trampoline;
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
*tramp++ = 0xf000f8df;
#else
*tramp++ = 0xf8dff000; /* not tested */
#endif
#else
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
*tramp++ = 0xe51ff004;
#else
*tramp++ = 0xe51ff004; /* not tested */
#endif
#endif
*tramp++ = (uint32_t) target;
return tramp;
#else
return set_arm_veneer(trampoline, target);
#endif
}
static void*
@@ -443,15 +453,10 @@ rtems_rtl_elf_reloc_rel (rtems_rtl_obj* obj,
addend = (tmp | ((sign ? 0 : 1) << 24)) - (1 << 24);
}
if (isThumb(symvalue)) ;/*Thumb to Thumb call, nothing to care */
else {
if (ELF_R_TYPE(rel->r_info) == R_TYPE(THM_JUMP24)) {
tmp = (tmp + 2) & ~3; /* aligned to 4 bytes only for JUMP24 */
}
else {
/* THM_CALL bl-->blx */
lower_insn &= ~(1<<12);
}
if (isThumb(symvalue) == false
&& ELF_R_TYPE(rel->r_info) != R_TYPE(THM_JUMP24)) {
/* THM_CALL bl-->blx */
lower_insn &= ~(1<<12);
}
if (parsing && sect->base == 0) {
@@ -461,7 +466,15 @@ rtems_rtl_elf_reloc_rel (rtems_rtl_obj* obj,
}
tmp = symvalue + addend;
tmp = tmp - (Elf_Addr)where;
if (isThumb(symvalue)) {
tmp = tmp - (Elf_Addr)where;
} else {
/*
* where[1:0] are set to 0 for ARM-targeted relocations because the jump
* offset[1:0] are also 0
*/
tmp = tmp - (Elf_Addr)((uintptr_t)where & 0xfffffffc);
}
if (isThumb(symvalue) == false && ELF_R_TYPE(rel->r_info) == R_TYPE(THM_JUMP24)) {
Elf_Word tramp_addr;
@@ -486,6 +499,7 @@ rtems_rtl_elf_reloc_rel (rtems_rtl_obj* obj,
tmp = tramp_addr + addend;
/* This targets a thumb trampoline, so no need to adjust the PC */
tmp = tmp - (Elf_Addr)where;
} else if (((Elf_Sword)tmp > 0x7fffff) || ((Elf_Sword)tmp < -0x800000)) {
Elf_Word tramp_addr;
@@ -506,11 +520,24 @@ rtems_rtl_elf_reloc_rel (rtems_rtl_obj* obj,
}
tramp_addr = ((Elf_Addr) obj->tramp_brk) | (symvalue & 1);
obj->tramp_brk = set_veneer(obj->tramp_brk, symvalue);
tmp = tramp_addr + addend;
tmp = tmp - (Elf_Addr)where;
if (isThumb(symvalue)) {
obj->tramp_brk = set_veneer(obj->tramp_brk, symvalue);
tmp = tmp - (Elf_Addr)where;
} else {
/*
* The B[L]X expects ARM code at the target. Align tramp_brk as
* necessary.
*/
obj->tramp_brk = (void *)RTEMS_ALIGN_UP((uintptr_t)obj->tramp_brk, 4);
tramp_addr = (Elf_Addr) obj->tramp_brk;
obj->tramp_brk = set_arm_veneer(obj->tramp_brk, symvalue);
/*
* where[1:0] are set to 0 for ARM-targeted relocations because the jump
* offset[1:0] are also 0
*/
tmp = tmp - (Elf_Addr)((uintptr_t)where & 0xfffffffc);
}
}
if (!parsing) {