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objtool: Fix seg fault with Clang non-section symbols 

The Clang assembler likes to strip section symbols, which means objtool
can't reference some text code by its section.  This confuses objtool
greatly, causing it to seg fault.

The fix is similar to what was done before, for ORC reloc generation:

  e81e072443 ("objtool: Support Clang non-section symbols in ORC generation")

Factor out that code into a common helper and use it for static call
reloc generation as well.

Reported-by: Arnd Bergmann <arnd@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://github.com/ClangBuiltLinux/linux/issues/1207
Link: https://lkml.kernel.org/r/ba6b6c0f0dd5acbba66e403955a967d9fdd1726a.1607983452.git.jpoimboe@redhat.com
zero-sugar-mainline-defconfig
Josh Poimboeuf 2020-12-14 16:04:20 -06:00 committed by Peter Zijlstra
parent 2c85ebc57b
commit 44f6a7c075
4 changed files with 42 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
tools/objtool/check.c
View File

@ -467,13 +467,20 @@ static int create_static_call_sections(struct objtool_file *file)
/* populate reloc for 'addr' */
reloc = malloc(sizeof(*reloc));
if (!reloc) {
perror("malloc");
return -1;
}
memset(reloc, 0, sizeof(*reloc));
reloc->sym = insn->sec->sym;
reloc->addend = insn->offset;
insn_to_reloc_sym_addend(insn->sec, insn->offset, reloc);
if (!reloc->sym) {
WARN_FUNC("static call tramp: missing containing symbol",
insn->sec, insn->offset);
return -1;
}
reloc->type = R_X86_64_PC32;
reloc->offset = idx * sizeof(struct static_call_site);
reloc->sec = reloc_sec;

26
tools/objtool/elf.c
View File

@ -262,6 +262,32 @@ struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, uns
return find_reloc_by_dest_range(elf, sec, offset, 1);
}
void insn_to_reloc_sym_addend(struct section *sec, unsigned long offset,
struct reloc *reloc)
{
if (sec->sym) {
reloc->sym = sec->sym;
reloc->addend = offset;
return;
}
/*
* The Clang assembler strips section symbols, so we have to reference
* the function symbol instead:
*/
reloc->sym = find_symbol_containing(sec, offset);
if (!reloc->sym) {
/*
* Hack alert. This happens when we need to reference the NOP
* pad insn immediately after the function.
*/
reloc->sym = find_symbol_containing(sec, offset - 1);
}
if (reloc->sym)
reloc->addend = offset - reloc->sym->offset;
}
static int read_sections(struct elf *elf)
{
Elf_Scn *s = NULL;

2
tools/objtool/elf.h
View File

@ -140,6 +140,8 @@ struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, uns
struct reloc *find_reloc_by_dest_range(const struct elf *elf, struct section *sec,
unsigned long offset, unsigned int len);
struct symbol *find_func_containing(struct section *sec, unsigned long offset);
void insn_to_reloc_sym_addend(struct section *sec, unsigned long offset,
struct reloc *reloc);
int elf_rebuild_reloc_section(struct elf *elf, struct section *sec);
#define for_each_sec(file, sec) \

29
tools/objtool/orc_gen.c
View File

@ -105,30 +105,11 @@ static int create_orc_entry(struct elf *elf, struct section *u_sec, struct secti
}
memset(reloc, 0, sizeof(*reloc));
if (insn_sec->sym) {
reloc->sym = insn_sec->sym;
reloc->addend = insn_off;
} else {
/*
* The Clang assembler doesn't produce section symbols, so we
* have to reference the function symbol instead:
*/
reloc->sym = find_symbol_containing(insn_sec, insn_off);
if (!reloc->sym) {
/*
* Hack alert. This happens when we need to reference
* the NOP pad insn immediately after the function.
*/
reloc->sym = find_symbol_containing(insn_sec,
insn_off - 1);
}
if (!reloc->sym) {
WARN("missing symbol for insn at offset 0x%lx\n",
insn_off);
return -1;
}
reloc->addend = insn_off - reloc->sym->offset;
insn_to_reloc_sym_addend(insn_sec, insn_off, reloc);
if (!reloc->sym) {
WARN("missing symbol for insn at offset 0x%lx",
insn_off);
return -1;
}
reloc->type = R_X86_64_PC32;