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SubjectRe: [PATCH 0/5] x86/kallsyms: Fix the call-thunk kallsyms fail
On Fri, Oct 28, 2022 at 09:40:22PM +0200, Peter Zijlstra wrote:
> Hi all,
>
> As reported here:
>
> https://lkml.kernel.org/r/202210241614.2ae4c1f5-yujie.liu@intel.com
>
> The kallsyms change for call-thunks doesn't really work out as expected. These
> patches revert that change and propose an alternative.

Robot found it needed the below; have folded back and pushed out again.

---
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index cf743520a786..55066c493570 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -3479,7 +3479,8 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,

if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
/* Ignore KCFI type preambles, which always fall through */
- if (!strncmp(func->name, "__cfi_", 6))
+ if (!strncmp(func->name, "__cfi_", 6) ||
+ !strncmp(func->name, "__pfx_", 6))
return 0;

WARN("%s() falls through to next function %s()",
@@ -4042,6 +4043,7 @@ static int add_prefix_symbol(struct objtool_file *file, struct symbol *func,

for (;;) {
struct instruction *prev = list_prev_entry(insn, list);
+ u64 offset;

if (&prev->list == &file->insn_list)
break;
@@ -4049,11 +4051,13 @@ static int add_prefix_symbol(struct objtool_file *file, struct symbol *func,
if (prev->type != INSN_NOP)
break;

- insn = prev;
- if (func->offset - prev->offset == opts.prefix) {
- elf_create_prefix_symbol(file->elf, func, -opts.prefix);
+ offset = func->offset - prev->offset;
+ if (offset >= opts.prefix) {
+ if (offset == opts.prefix)
+ elf_create_prefix_symbol(file->elf, func, opts.prefix);
break;
}
+ insn = prev;
}

return 0;
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 9fbdad7a565d..3d636d12d679 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -822,7 +822,7 @@ elf_create_section_symbol(struct elf *elf, struct section *sec)
static int elf_add_string(struct elf *elf, struct section *strtab, char *str);

struct symbol *
-elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, long addend)
+elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, long size)
{
struct symbol *sym = calloc(1, sizeof(*sym));
size_t namelen = strlen(orig->name) + sizeof("__pfx_");
@@ -840,7 +840,8 @@ elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, long addend)

sym->sym.st_name = elf_add_string(elf, NULL, name);
sym->sym.st_info = orig->sym.st_info;
- sym->sym.st_value = orig->sym.st_value + addend;
+ sym->sym.st_value = orig->sym.st_value - size;
+ sym->sym.st_size = size;

sym = __elf_create_symbol(elf, sym);
if (sym)
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index 9e3bd4717a11..b6974e3173aa 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -146,7 +146,7 @@ static inline bool has_multiple_files(struct elf *elf)
struct elf *elf_open_read(const char *name, int flags);
struct section *elf_create_section(struct elf *elf, const char *name, unsigned int sh_flags, size_t entsize, int nr);

-struct symbol *elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, long addend);
+struct symbol *elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, long size);

int elf_add_reloc(struct elf *elf, struct section *sec, unsigned long offset,
unsigned int type, struct symbol *sym, s64 addend);
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