2023-07-25 11:44:07

by James Clark

Subject: [PATCH v2] scripts/kallsyms: Fix build failure by setting errno before calling getline()

getline() returns -1 at EOF as well as on error. It also doesn't set
errno to 0 on success, so initialize it to 0 before using errno to check
for an error condition. See the paragraph here [1]:

For some system calls and library functions (e.g., getpriority(2)),
-1 is a valid return on success. In such cases, a successful return
can be distinguished from an error return by setting errno to zero
before the call, and then, if the call returns a status that indicates
that an error may have occurred, checking to see if errno has a
nonzero value.

Bear has a bug [2] that launches processes with errno set and causes the
following build failure:

$ bear -- make LLVM=1
...
LD .tmp_vmlinux.kallsyms1
NM .tmp_vmlinux.kallsyms1.syms
KSYMS .tmp_vmlinux.kallsyms1.S
read_symbol: Invalid argument

[1]: https://linux.die.net/man/3/errno
[2]: https://github.com/rizsotto/Bear/issues/469

Fixes: 1c975da56a6f ("scripts/kallsyms: remove KSYM_NAME_LEN_BUFFER")
Reviewed-by: Miguel Ojeda <[email protected]>
Signed-off-by: James Clark <[email protected]>
---
scripts/kallsyms.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index 16c87938b316..653b92f6d4c8 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -129,6 +129,7 @@ static struct sym_entry *read_symbol(FILE *in, char **buf, size_t *buf_len)
ssize_t readlen;
struct sym_entry *sym;

+ errno = 0;
readlen = getline(buf, buf_len, in);
if (readlen < 0) {
if (errno) {
--
2.34.1

2023-07-29 07:54:24

by Masahiro Yamada

Subject: Re: [PATCH v2] scripts/kallsyms: Fix build failure by setting errno before calling getline()

On Tue, Jul 25, 2023 at 7:58 PM James Clark <[email protected]> wrote:
>
> getline() returns -1 at EOF as well as on error. It also doesn't set
> errno to 0 on success, so initialize it to 0 before using errno to check
> for an error condition. See the paragraph here [1]:
>
> For some system calls and library functions (e.g., getpriority(2)),
> -1 is a valid return on success. In such cases, a successful return
> can be distinguished from an error return by setting errno to zero
> before the call, and then, if the call returns a status that indicates
> that an error may have occurred, checking to see if errno has a
> nonzero value.
>
> Bear has a bug [2] that launches processes with errno set and causes the
> following build failure:
>
> $ bear -- make LLVM=1
> ...
> LD .tmp_vmlinux.kallsyms1
> NM .tmp_vmlinux.kallsyms1.syms
> KSYMS .tmp_vmlinux.kallsyms1.S
> read_symbol: Invalid argument
>
> [1]: https://linux.die.net/man/3/errno
> [2]: https://github.com/rizsotto/Bear/issues/469
>
> Fixes: 1c975da56a6f ("scripts/kallsyms: remove KSYM_NAME_LEN_BUFFER")
> Reviewed-by: Miguel Ojeda <[email protected]>
> Signed-off-by: James Clark <[email protected]>

Applied to linux-kbuild/fixes.
Thanks.


> ---
> scripts/kallsyms.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
> index 16c87938b316..653b92f6d4c8 100644
> --- a/scripts/kallsyms.c
> +++ b/scripts/kallsyms.c
> @@ -129,6 +129,7 @@ static struct sym_entry *read_symbol(FILE *in, char **buf, size_t *buf_len)
> ssize_t readlen;
> struct sym_entry *sym;
>
> + errno = 0;
> readlen = getline(buf, buf_len, in);
> if (readlen < 0) {
> if (errno) {
> --
> 2.34.1
>


--
Best Regards
Masahiro Yamada