tools/lib/bpf/elf.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
In `elf_close`, we get this with GCC 15 -O3 (at least):
```
In function ‘elf_close’,
inlined from ‘elf_close’ at elf.c:53:6,
inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2:
elf.c:57:9: warning: ‘elf_fd.elf’ may be used uninitialized [-Wmaybe-uninitialized]
57 | elf_end(elf_fd->elf);
| ^~~~~~~~~~~~~~~~~~~~
elf.c: In function ‘elf_find_func_offset_from_file’:
elf.c:377:23: note: ‘elf_fd.elf’ was declared here
377 | struct elf_fd elf_fd;
| ^~~~~~
In function ‘elf_close’,
inlined from ‘elf_close’ at elf.c:53:6,
inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2:
elf.c:58:9: warning: ‘elf_fd.fd’ may be used uninitialized [-Wmaybe-uninitialized]
58 | close(elf_fd->fd);
| ^~~~~~~~~~~~~~~~~
elf.c: In function ‘elf_find_func_offset_from_file’:
elf.c:377:23: note: ‘elf_fd.fd’ was declared here
377 | struct elf_fd elf_fd;
| ^~~~~~
```
In reality, our use is fine, it's just that GCC doesn't model errno
here (see linked GCC bug). Suppress -Wmaybe-uninitialized accordingly
by initializing elf_fd.elf to -1.
I've done this in two other functions as well given it could easily
occur there too (same access/use pattern).
Link: https://gcc.gnu.org/PR114952
Signed-off-by: Sam James <sam@gentoo.org>
---
v3: Initialize to -1 instead of using a pragma.
Range-diff against v2:
1: 8f5c3b173e4cb < -: ------------- libbpf: workaround -Wmaybe-uninitialized false positive
-: ------------- > 1: 12cec1262be71 libbpf: workaround -Wmaybe-uninitialized false positive
tools/lib/bpf/elf.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
index c92e02394159e..00ea3f867bbc8 100644
--- a/tools/lib/bpf/elf.c
+++ b/tools/lib/bpf/elf.c
@@ -374,7 +374,7 @@ long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name)
*/
long elf_find_func_offset_from_file(const char *binary_path, const char *name)
{
- struct elf_fd elf_fd;
+ struct elf_fd elf_fd = { .fd = -1 };
long ret = -ENOENT;
ret = elf_open(binary_path, &elf_fd);
@@ -412,7 +412,7 @@ int elf_resolve_syms_offsets(const char *binary_path, int cnt,
int err = 0, i, cnt_done = 0;
unsigned long *offsets;
struct symbol *symbols;
- struct elf_fd elf_fd;
+ struct elf_fd elf_fd = { .fd = -1 };
err = elf_open(binary_path, &elf_fd);
if (err)
@@ -507,7 +507,7 @@ int elf_resolve_pattern_offsets(const char *binary_path, const char *pattern,
int sh_types[2] = { SHT_SYMTAB, SHT_DYNSYM };
unsigned long *offsets = NULL;
size_t cap = 0, cnt = 0;
- struct elf_fd elf_fd;
+ struct elf_fd elf_fd = { .fd = -1 };
int err = 0, i;
err = elf_open(binary_path, &elf_fd);
--
2.45.2
On 12/08/2024 11:37, Sam James wrote:
> In `elf_close`, we get this with GCC 15 -O3 (at least):
> ```
> In function ‘elf_close’,
> inlined from ‘elf_close’ at elf.c:53:6,
> inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2:
> elf.c:57:9: warning: ‘elf_fd.elf’ may be used uninitialized [-Wmaybe-uninitialized]
> 57 | elf_end(elf_fd->elf);
> | ^~~~~~~~~~~~~~~~~~~~
> elf.c: In function ‘elf_find_func_offset_from_file’:
> elf.c:377:23: note: ‘elf_fd.elf’ was declared here
> 377 | struct elf_fd elf_fd;
> | ^~~~~~
> In function ‘elf_close’,
> inlined from ‘elf_close’ at elf.c:53:6,
> inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2:
> elf.c:58:9: warning: ‘elf_fd.fd’ may be used uninitialized [-Wmaybe-uninitialized]
> 58 | close(elf_fd->fd);
> | ^~~~~~~~~~~~~~~~~
> elf.c: In function ‘elf_find_func_offset_from_file’:
> elf.c:377:23: note: ‘elf_fd.fd’ was declared here
> 377 | struct elf_fd elf_fd;
> | ^~~~~~
> ```
>
> In reality, our use is fine, it's just that GCC doesn't model errno
> here (see linked GCC bug). Suppress -Wmaybe-uninitialized accordingly
> by initializing elf_fd.elf to -1.
>
> I've done this in two other functions as well given it could easily
> occur there too (same access/use pattern).
>
hmm, looking at this again - given that there are multiple consumers -
I suppose another option would perhaps be to
- have elf_open() to init int fd = -1, Elf *elf = NULL.
- have error paths in elf_open() "goto out"; at out: we set elf_fd->fd,
elf_fd->elf to fd, elf
- have elf_close() exit it elf_fd < 0 (since 0 is a valid fd), as it
will for the error cases
Might all be bit excessive, and might not even fix the false positive
issue here, so
> Link: https://gcc.gnu.org/PR114952
> Signed-off-by: Sam James <sam@gentoo.org>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
> ---
> v3: Initialize to -1 instead of using a pragma.
>
> Range-diff against v2:
> 1: 8f5c3b173e4cb < -: ------------- libbpf: workaround -Wmaybe-uninitialized false positive
> -: ------------- > 1: 12cec1262be71 libbpf: workaround -Wmaybe-uninitialized false positive
>
> tools/lib/bpf/elf.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
> index c92e02394159e..00ea3f867bbc8 100644
> --- a/tools/lib/bpf/elf.c
> +++ b/tools/lib/bpf/elf.c
> @@ -374,7 +374,7 @@ long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name)
> */
> long elf_find_func_offset_from_file(const char *binary_path, const char *name)
> {
> - struct elf_fd elf_fd;
> + struct elf_fd elf_fd = { .fd = -1 };
> long ret = -ENOENT;
>
> ret = elf_open(binary_path, &elf_fd);
> @@ -412,7 +412,7 @@ int elf_resolve_syms_offsets(const char *binary_path, int cnt,
> int err = 0, i, cnt_done = 0;
> unsigned long *offsets;
> struct symbol *symbols;
> - struct elf_fd elf_fd;
> + struct elf_fd elf_fd = { .fd = -1 };
>
> err = elf_open(binary_path, &elf_fd);
> if (err)
> @@ -507,7 +507,7 @@ int elf_resolve_pattern_offsets(const char *binary_path, const char *pattern,
> int sh_types[2] = { SHT_SYMTAB, SHT_DYNSYM };
> unsigned long *offsets = NULL;
> size_t cap = 0, cnt = 0;
> - struct elf_fd elf_fd;
> + struct elf_fd elf_fd = { .fd = -1 };
> int err = 0, i;
>
> err = elf_open(binary_path, &elf_fd);
On Mon, Aug 12, 2024 at 6:57 AM Alan Maguire <alan.maguire@oracle.com> wrote:
>
> On 12/08/2024 11:37, Sam James wrote:
> > In `elf_close`, we get this with GCC 15 -O3 (at least):
> > ```
> > In function ‘elf_close’,
> > inlined from ‘elf_close’ at elf.c:53:6,
> > inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2:
> > elf.c:57:9: warning: ‘elf_fd.elf’ may be used uninitialized [-Wmaybe-uninitialized]
> > 57 | elf_end(elf_fd->elf);
> > | ^~~~~~~~~~~~~~~~~~~~
> > elf.c: In function ‘elf_find_func_offset_from_file’:
> > elf.c:377:23: note: ‘elf_fd.elf’ was declared here
> > 377 | struct elf_fd elf_fd;
> > | ^~~~~~
> > In function ‘elf_close’,
> > inlined from ‘elf_close’ at elf.c:53:6,
> > inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2:
> > elf.c:58:9: warning: ‘elf_fd.fd’ may be used uninitialized [-Wmaybe-uninitialized]
> > 58 | close(elf_fd->fd);
> > | ^~~~~~~~~~~~~~~~~
> > elf.c: In function ‘elf_find_func_offset_from_file’:
> > elf.c:377:23: note: ‘elf_fd.fd’ was declared here
> > 377 | struct elf_fd elf_fd;
> > | ^~~~~~
> > ```
> >
> > In reality, our use is fine, it's just that GCC doesn't model errno
> > here (see linked GCC bug). Suppress -Wmaybe-uninitialized accordingly
> > by initializing elf_fd.elf to -1.
> >
> > I've done this in two other functions as well given it could easily
> > occur there too (same access/use pattern).
> >
>
> hmm, looking at this again - given that there are multiple consumers -
yes, I don't like that each caller has to remember to initialize the
struct that is clearly initialized by elf_open() itself, so see below.
pw-bot: cr
> I suppose another option would perhaps be to
>
> - have elf_open() to init int fd = -1, Elf *elf = NULL.
I'd do just
elf_fd->elf = NULL;
elf_fd->fd = -1;
and do nothing else. This should be enough for compiler to not trigger this.
> - have error paths in elf_open() "goto out"; at out: we set elf_fd->fd,
> elf_fd->elf to fd, elf
> - have elf_close() exit it elf_fd < 0 (since 0 is a valid fd), as it
> will for the error cases
>
Let's not touch anything else, this should be enough.
> Might all be bit excessive, and might not even fix the false positive
> issue here, so
>
> > Link: https://gcc.gnu.org/PR114952
> > Signed-off-by: Sam James <sam@gentoo.org>
>
> Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
>
> > ---
> > v3: Initialize to -1 instead of using a pragma.
> >
> > Range-diff against v2:
> > 1: 8f5c3b173e4cb < -: ------------- libbpf: workaround -Wmaybe-uninitialized false positive
> > -: ------------- > 1: 12cec1262be71 libbpf: workaround -Wmaybe-uninitialized false positive
> >
> > tools/lib/bpf/elf.c | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
> > index c92e02394159e..00ea3f867bbc8 100644
> > --- a/tools/lib/bpf/elf.c
> > +++ b/tools/lib/bpf/elf.c
> > @@ -374,7 +374,7 @@ long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name)
> > */
> > long elf_find_func_offset_from_file(const char *binary_path, const char *name)
> > {
> > - struct elf_fd elf_fd;
> > + struct elf_fd elf_fd = { .fd = -1 };
> > long ret = -ENOENT;
> >
> > ret = elf_open(binary_path, &elf_fd);
> > @@ -412,7 +412,7 @@ int elf_resolve_syms_offsets(const char *binary_path, int cnt,
> > int err = 0, i, cnt_done = 0;
> > unsigned long *offsets;
> > struct symbol *symbols;
> > - struct elf_fd elf_fd;
> > + struct elf_fd elf_fd = { .fd = -1 };
> >
> > err = elf_open(binary_path, &elf_fd);
> > if (err)
> > @@ -507,7 +507,7 @@ int elf_resolve_pattern_offsets(const char *binary_path, const char *pattern,
> > int sh_types[2] = { SHT_SYMTAB, SHT_DYNSYM };
> > unsigned long *offsets = NULL;
> > size_t cap = 0, cnt = 0;
> > - struct elf_fd elf_fd;
> > + struct elf_fd elf_fd = { .fd = -1 };
> > int err = 0, i;
> >
> > err = elf_open(binary_path, &elf_fd);
Andrii Nakryiko <andrii.nakryiko@gmail.com> writes:
> On Mon, Aug 12, 2024 at 6:57 AM Alan Maguire <alan.maguire@oracle.com> wrote:
>>
>> On 12/08/2024 11:37, Sam James wrote:
>> > In `elf_close`, we get this with GCC 15 -O3 (at least):
>> > ```
>> > In function ‘elf_close’,
>> > inlined from ‘elf_close’ at elf.c:53:6,
>> > inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2:
>> > elf.c:57:9: warning: ‘elf_fd.elf’ may be used uninitialized [-Wmaybe-uninitialized]
>> > 57 | elf_end(elf_fd->elf);
>> > | ^~~~~~~~~~~~~~~~~~~~
>> > elf.c: In function ‘elf_find_func_offset_from_file’:
>> > elf.c:377:23: note: ‘elf_fd.elf’ was declared here
>> > 377 | struct elf_fd elf_fd;
>> > | ^~~~~~
>> > In function ‘elf_close’,
>> > inlined from ‘elf_close’ at elf.c:53:6,
>> > inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2:
>> > elf.c:58:9: warning: ‘elf_fd.fd’ may be used uninitialized [-Wmaybe-uninitialized]
>> > 58 | close(elf_fd->fd);
>> > | ^~~~~~~~~~~~~~~~~
>> > elf.c: In function ‘elf_find_func_offset_from_file’:
>> > elf.c:377:23: note: ‘elf_fd.fd’ was declared here
>> > 377 | struct elf_fd elf_fd;
>> > | ^~~~~~
>> > ```
>> >
>> > In reality, our use is fine, it's just that GCC doesn't model errno
>> > here (see linked GCC bug). Suppress -Wmaybe-uninitialized accordingly
>> > by initializing elf_fd.elf to -1.
>> >
>> > I've done this in two other functions as well given it could easily
>> > occur there too (same access/use pattern).
>> >
>>
>> hmm, looking at this again - given that there are multiple consumers -
>
> yes, I don't like that each caller has to remember to initialize the
> struct that is clearly initialized by elf_open() itself, so see below.
>
> pw-bot: cr
>
>> I suppose another option would perhaps be to
>>
>> - have elf_open() to init int fd = -1, Elf *elf = NULL.
>
> I'd do just
>
> elf_fd->elf = NULL;
> elf_fd->fd = -1;
>
> and do nothing else. This should be enough for compiler to not trigger this.
OK.
>
>> - have error paths in elf_open() "goto out"; at out: we set elf_fd->fd,
>> elf_fd->elf to fd, elf
>> - have elf_close() exit it elf_fd < 0 (since 0 is a valid fd), as it
>> will for the error cases
>>
>
> Let's not touch anything else, this should be enough.
>
>
>> Might all be bit excessive, and might not even fix the false positive
>> issue here, so
>>
>> > Link: https://gcc.gnu.org/PR114952
>> > Signed-off-by: Sam James <sam@gentoo.org>
>>
>> Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
>>
>> > ---
>> > v3: Initialize to -1 instead of using a pragma.
>> >
>> > Range-diff against v2:
>> > 1: 8f5c3b173e4cb < -: ------------- libbpf: workaround -Wmaybe-uninitialized false positive
>> > -: ------------- > 1: 12cec1262be71 libbpf: workaround -Wmaybe-uninitialized false positive
>> >
>> > tools/lib/bpf/elf.c | 6 +++---
>> > 1 file changed, 3 insertions(+), 3 deletions(-)
>> >
>> > diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
>> > index c92e02394159e..00ea3f867bbc8 100644
>> > --- a/tools/lib/bpf/elf.c
>> > +++ b/tools/lib/bpf/elf.c
>> > @@ -374,7 +374,7 @@ long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name)
>> > */
>> > long elf_find_func_offset_from_file(const char *binary_path, const char *name)
>> > {
>> > - struct elf_fd elf_fd;
>> > + struct elf_fd elf_fd = { .fd = -1 };
>> > long ret = -ENOENT;
>> >
>> > ret = elf_open(binary_path, &elf_fd);
>> > @@ -412,7 +412,7 @@ int elf_resolve_syms_offsets(const char *binary_path, int cnt,
>> > int err = 0, i, cnt_done = 0;
>> > unsigned long *offsets;
>> > struct symbol *symbols;
>> > - struct elf_fd elf_fd;
>> > + struct elf_fd elf_fd = { .fd = -1 };
>> >
>> > err = elf_open(binary_path, &elf_fd);
>> > if (err)
>> > @@ -507,7 +507,7 @@ int elf_resolve_pattern_offsets(const char *binary_path, const char *pattern,
>> > int sh_types[2] = { SHT_SYMTAB, SHT_DYNSYM };
>> > unsigned long *offsets = NULL;
>> > size_t cap = 0, cnt = 0;
>> > - struct elf_fd elf_fd;
>> > + struct elf_fd elf_fd = { .fd = -1 };
>> > int err = 0, i;
>> >
>> > err = elf_open(binary_path, &elf_fd);
On Mon, Aug 12, 2024 at 11:37:59AM +0100, Sam James wrote:
> In `elf_close`, we get this with GCC 15 -O3 (at least):
> ```
> In function ‘elf_close’,
> inlined from ‘elf_close’ at elf.c:53:6,
> inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2:
> elf.c:57:9: warning: ‘elf_fd.elf’ may be used uninitialized [-Wmaybe-uninitialized]
> 57 | elf_end(elf_fd->elf);
> | ^~~~~~~~~~~~~~~~~~~~
> elf.c: In function ‘elf_find_func_offset_from_file’:
> elf.c:377:23: note: ‘elf_fd.elf’ was declared here
> 377 | struct elf_fd elf_fd;
> | ^~~~~~
> In function ‘elf_close’,
> inlined from ‘elf_close’ at elf.c:53:6,
> inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2:
> elf.c:58:9: warning: ‘elf_fd.fd’ may be used uninitialized [-Wmaybe-uninitialized]
> 58 | close(elf_fd->fd);
> | ^~~~~~~~~~~~~~~~~
> elf.c: In function ‘elf_find_func_offset_from_file’:
> elf.c:377:23: note: ‘elf_fd.fd’ was declared here
> 377 | struct elf_fd elf_fd;
> | ^~~~~~
> ```
>
> In reality, our use is fine, it's just that GCC doesn't model errno
> here (see linked GCC bug). Suppress -Wmaybe-uninitialized accordingly
> by initializing elf_fd.elf to -1.
>
> I've done this in two other functions as well given it could easily
> occur there too (same access/use pattern).
>
> Link: https://gcc.gnu.org/PR114952
> Signed-off-by: Sam James <sam@gentoo.org>
> ---
> v3: Initialize to -1 instead of using a pragma.
it's false positive, but I wonder we could still add Fixes tag
Acked-by: Jiri Olsa <jolsa@kernel.org>
jirka
>
> Range-diff against v2:
> 1: 8f5c3b173e4cb < -: ------------- libbpf: workaround -Wmaybe-uninitialized false positive
> -: ------------- > 1: 12cec1262be71 libbpf: workaround -Wmaybe-uninitialized false positive
>
> tools/lib/bpf/elf.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
> index c92e02394159e..00ea3f867bbc8 100644
> --- a/tools/lib/bpf/elf.c
> +++ b/tools/lib/bpf/elf.c
> @@ -374,7 +374,7 @@ long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name)
> */
> long elf_find_func_offset_from_file(const char *binary_path, const char *name)
> {
> - struct elf_fd elf_fd;
> + struct elf_fd elf_fd = { .fd = -1 };
> long ret = -ENOENT;
>
> ret = elf_open(binary_path, &elf_fd);
> @@ -412,7 +412,7 @@ int elf_resolve_syms_offsets(const char *binary_path, int cnt,
> int err = 0, i, cnt_done = 0;
> unsigned long *offsets;
> struct symbol *symbols;
> - struct elf_fd elf_fd;
> + struct elf_fd elf_fd = { .fd = -1 };
>
> err = elf_open(binary_path, &elf_fd);
> if (err)
> @@ -507,7 +507,7 @@ int elf_resolve_pattern_offsets(const char *binary_path, const char *pattern,
> int sh_types[2] = { SHT_SYMTAB, SHT_DYNSYM };
> unsigned long *offsets = NULL;
> size_t cap = 0, cnt = 0;
> - struct elf_fd elf_fd;
> + struct elf_fd elf_fd = { .fd = -1 };
> int err = 0, i;
>
> err = elf_open(binary_path, &elf_fd);
> --
> 2.45.2
>
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