Le 09/04/2020 à 17:27, Alex Bennée a écrit :
> Brice Goglin <brice.gog...@inria.fr> writes:
>
>> When the program name is very long, qemu-user may truncate it in
>> /proc/self/stat. However the truncation must keep the ending ") "
>> to conform to the proc manpage which says:
>> (2) comm %s
>> The filename of the executable, in parentheses. This
>> is visible whether or not the executable is swapped
>> out.
>>
>> To reproduce:
>> $ ln -s /bin/cat <filenamewithmorethan128chars>
>> $ qemu-x86_64 ./<filenamewithmorethan128chars> /proc/self/stat
>>
>> Before the patch, you get:
>> 1134631 (<filenametruncated>0 0 0 0 0 0 0 0 ...
>> After the patch:
>> 1134631 (<filenametruncat>) 0 0 0 0 0 0 0 0 ...
>>
>> This fixes an issue with hwloc failing to parse /proc/self/stat
>> when Ludovic Courtes was testing it in Guix over qemu-aarch64.
>>
>> Signed-off-by: Philippe_Mathieu-Daudé <phi...@redhat.com>
>> Signed-off-by: Brice Goglin <brice.gog...@inria.fr>
>>
>> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
>> --- a/linux-user/syscall.c
>> +++ b/linux-user/syscall.c
>> @@ -7305,7 +7305,11 @@ static int open_self_stat(void *cpu_env, int fd)
>> snprintf(buf, sizeof(buf), "%"PRId64 " ", val);
>> } else if (i == 1) {
>> /* app name */
>> - snprintf(buf, sizeof(buf), "(%s) ", ts->bprm->argv[0]);
>> + char *ptr = buf;
>> +
>> + *ptr++ = '(';
>> + ptr = stpncpy(ptr, ts->bprm->argv[0], sizeof(buf) - 3);
>> + strcpy(ptr, ") ");
> why not just use a format string:
>
> snprintf(buf, sizeof(buf), "(%.125s) ", ts->bprm->argv[0]);
>
Go ahead and apply what you want (maybe 124 instead of 125 because of
the ending \0).
My commit message above explains how to test things very quickly.
I don't use qemu-user or Guix myself, and I can't spend time
debugging/testing this further.
Thank you
Brice
