mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-05 18:39:59 +00:00
libbpf: Handle GCC noreturn-turned-volatile quirk
Handle a GCC quirk of emitting extra volatile modifier in DWARF (and
subsequently preserved in BTF by pahole) for function pointers marked as
__attribute__((noreturn)). This was the way to mark such functions before GCC
2.5 added noreturn attribute. Drop such func_proto modifiers, similarly to how
it's done for array (also to handle GCC quirk/bug).
Such volatile attribute is emitted by GCC only, so existing selftests can't
express such test. Simple repro is like this (compiled with GCC + BTF
generated by pahole):
struct my_struct {
void __attribute__((noreturn)) (*fn)(int);
};
struct my_struct a;
Without this fix, output will be:
struct my_struct {
voidvolatile (*fn)(int);
};
With the fix:
struct my_struct {
void (*fn)(int);
};
Fixes: 351131b51c
("libbpf: add btf_dump API for BTF-to-C conversion")
Reported-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/bpf/20200610052335.2862559-1-andriin@fb.com
This commit is contained in:
parent
8ca8d4a841
commit
32022fd97e
1 changed files with 24 additions and 9 deletions
|
@ -1137,6 +1137,20 @@ static void btf_dump_emit_mods(struct btf_dump *d, struct id_stack *decl_stack)
|
||||||
}
|
}
|
||||||
}
|
}
|
||||||
|
|
||||||
|
static void btf_dump_drop_mods(struct btf_dump *d, struct id_stack *decl_stack)
|
||||||
|
{
|
||||||
|
const struct btf_type *t;
|
||||||
|
__u32 id;
|
||||||
|
|
||||||
|
while (decl_stack->cnt) {
|
||||||
|
id = decl_stack->ids[decl_stack->cnt - 1];
|
||||||
|
t = btf__type_by_id(d->btf, id);
|
||||||
|
if (!btf_is_mod(t))
|
||||||
|
return;
|
||||||
|
decl_stack->cnt--;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
static void btf_dump_emit_name(const struct btf_dump *d,
|
static void btf_dump_emit_name(const struct btf_dump *d,
|
||||||
const char *name, bool last_was_ptr)
|
const char *name, bool last_was_ptr)
|
||||||
{
|
{
|
||||||
|
@ -1235,14 +1249,7 @@ static void btf_dump_emit_type_chain(struct btf_dump *d,
|
||||||
* a const/volatile modifier for array, so we are
|
* a const/volatile modifier for array, so we are
|
||||||
* going to silently skip them here.
|
* going to silently skip them here.
|
||||||
*/
|
*/
|
||||||
while (decls->cnt) {
|
btf_dump_drop_mods(d, decls);
|
||||||
next_id = decls->ids[decls->cnt - 1];
|
|
||||||
next_t = btf__type_by_id(d->btf, next_id);
|
|
||||||
if (btf_is_mod(next_t))
|
|
||||||
decls->cnt--;
|
|
||||||
else
|
|
||||||
break;
|
|
||||||
}
|
|
||||||
|
|
||||||
if (decls->cnt == 0) {
|
if (decls->cnt == 0) {
|
||||||
btf_dump_emit_name(d, fname, last_was_ptr);
|
btf_dump_emit_name(d, fname, last_was_ptr);
|
||||||
|
@ -1270,7 +1277,15 @@ static void btf_dump_emit_type_chain(struct btf_dump *d,
|
||||||
__u16 vlen = btf_vlen(t);
|
__u16 vlen = btf_vlen(t);
|
||||||
int i;
|
int i;
|
||||||
|
|
||||||
btf_dump_emit_mods(d, decls);
|
/*
|
||||||
|
* GCC emits extra volatile qualifier for
|
||||||
|
* __attribute__((noreturn)) function pointers. Clang
|
||||||
|
* doesn't do it. It's a GCC quirk for backwards
|
||||||
|
* compatibility with code written for GCC <2.5. So,
|
||||||
|
* similarly to extra qualifiers for array, just drop
|
||||||
|
* them, instead of handling them.
|
||||||
|
*/
|
||||||
|
btf_dump_drop_mods(d, decls);
|
||||||
if (decls->cnt) {
|
if (decls->cnt) {
|
||||||
btf_dump_printf(d, " (");
|
btf_dump_printf(d, " (");
|
||||||
btf_dump_emit_type_chain(d, decls, fname, lvl);
|
btf_dump_emit_type_chain(d, decls, fname, lvl);
|
||||||
|
|
Loading…
Reference in a new issue