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llext: Full ARM ELF relocation support

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Adds support for all relocation type produced by GCC
on ARM platform using partial linking (-r flag) or
shared link (-fpic and -shared flag).

Signed-off-by: Cedric Lescop <cedric.lescop@se.com>
This commit is contained in:
Cedric Lescop 2024-04-10 11:05:26 +02:00 • committed by Anas Nashif
commit 7b1d9d6166
4 changed files with 366 additions and 58 deletions
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27
subsys/llext/llext.c
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@ -714,8 +714,10 @@ static void llext_link_plt(struct llext_loader *ldr, struct llext *ext,
}
}
__weak void arch_elf_relocate(elf_rela_t *rel, uintptr_t opaddr, uintptr_t opval)
__weak int arch_elf_relocate(elf_rela_t *rel, uintptr_t loc,
uintptr_t sym_base_addr, const char *sym_name, uintptr_t load_bias)
{
return -EOPNOTSUPP;
}
static int llext_link(struct llext_loader *ldr, struct llext *ext, bool do_local)
@ -773,6 +775,9 @@ static int llext_link(struct llext_loader *ldr, struct llext *ext, bool do_local
if (tgt)
llext_link_plt(ldr, ext, &shdr, do_local, tgt);
continue;
} else if (strcmp(name, ".rel.dyn") == 0) {
/* we assume that first load segment starts at MEM_TEXT */
loc = (uintptr_t)ext->mem[LLEXT_MEM_TEXT];
}
LOG_DBG("relocation section %s (%d) linked to section %d has %zd relocations",
@ -815,8 +820,11 @@ static int llext_link(struct llext_loader *ldr, struct llext *ext, bool do_local
op_loc = loc + rel.r_offset;
/* If symbol is undefined, then we need to look it up */
if (sym.st_shndx == SHN_UNDEF) {
if (ELF_R_SYM(rel.r_info) == 0) {
/* no symbol ex: R_ARM_V4BX relocation, R_ARM_RELATIVE */
link_addr = 0;
} else if (sym.st_shndx == SHN_UNDEF) {
/* If symbol is undefined, then we need to look it up */
link_addr = (uintptr_t)llext_find_sym(NULL, name);
if (link_addr == 0) {
@ -824,6 +832,8 @@ static int llext_link(struct llext_loader *ldr, struct llext *ext, bool do_local
"symbol table %s, offset %zd, link section %d",
name, (size_t)rel.r_offset, shdr.sh_link);
return -ENODATA;
} else {
LOG_INF("found symbol %s at 0x%lx", name, link_addr);
}
} else if (ELF_ST_TYPE(sym.st_info) == STT_SECTION ||
ELF_ST_TYPE(sym.st_info) == STT_FUNC ||
@ -839,18 +849,17 @@ static int llext_link(struct llext_loader *ldr, struct llext *ext, bool do_local
continue;
}
LOG_INF("relocating (linking) symbol %s type %d binding %d ndx %d offset "
"%zd link section %d",
name, ELF_ST_TYPE(sym.st_info), ELF_ST_BIND(sym.st_info),
sym.st_shndx, (size_t)rel.r_offset, shdr.sh_link);
LOG_INF("writing relocation symbol %s type %zd sym %zd at addr 0x%lx "
"addr 0x%lx",
name, (size_t)ELF_R_TYPE(rel.r_info), (size_t)ELF_R_SYM(rel.r_info),
op_loc, link_addr);
/* relocation */
arch_elf_relocate(&rel, op_loc, link_addr);
ret = arch_elf_relocate(&rel, op_loc, link_addr, name,
(uintptr_t)ext->mem[LLEXT_MEM_TEXT]);
if (ret != 0) {
return ret;
}
}
}