Hello Alex, Shawn, and Nora,
@Nora, thanks for the bug report.
On 7/28/21 10:20 PM, Alejandro Colomar wrote:
> From: Shawn Landden <shawn@xxxxxxx>
>
> The absolute pathname is available in the Linux-specific
> auxiliary-vector feature.
@Shawn
But this isn't true, as far as I can see. See the following:
[[
$ cat auxv.c
#include <link.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
extern char **environ;
int
main(int argc, char *argv[])
{
char **p;
/* Walk through the array of pointers in environ */
for (p = environ; *p != NULL; p++)
continue;
/* The auxiliary vector sits just above environ */
p++; /* Step past NULL pointer at end of 'environ' */
printf("auxvec %12p\n", (void *) p);
ElfW(auxv_t) *auxv = (ElfW(auxv_t) *) p;
while (auxv->a_type != 0) {
switch (auxv->a_type) {
case AT_PLATFORM:
/* String identifying hardware platform */
printf("AT_PLATFORM: 0x%llx (string: %s)\n",
(long long) auxv->a_un.a_val, (char *) auxv->a_un.a_val);
break;
case AT_SECURE: /* Was secure-execution mode triggered for dynamic
linker? See ld.so(8). */
printf("AT_SECURE: %lld\n", (long long) auxv->a_un.a_val);
break;
case AT_EXECFN: /* Pathname used to execute program */
printf("AT_EXECFN: 0x%llx (string: %s)\n",
(long long) auxv->a_un.a_val, (char *) auxv->a_un.a_val);
break;
default:
/* We ignore other types of entries in auxiliary vector */
break;
}
auxv++;
}
exit(EXIT_SUCCESS);
}
$ ./auxv
auxvec 0x7ffd5c6eb708
AT_SECURE: 0
AT_EXECFN: 0x7ffd5c6ecff1 (string: ./auxv)
AT_PLATFORM: 0x7ffd5c6eb859 (string: x86_64)
]]
>
> Reported-by: Nora Platiel <nplatiel@xxxxxx>
> Signed-off-by: Shawn Landden <shawn@xxxxxxx>
> Reviewed-by: Nora Platiel <nplatiel@xxxxxx>
> Signed-off-by: Alejandro Colomar <alx.manpages@xxxxxxxxx>
> ---
> man2/execve.2 | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/man2/execve.2 b/man2/execve.2
> index c18ca5412..7fe12ab42 100644
> --- a/man2/execve.2
> +++ b/man2/execve.2
> @@ -346,7 +346,9 @@ will be invoked with the following arguments:
> .PP
> where
> .I pathname
> -is the absolute pathname of the file specified as the first argument of
> +is the absolute pathname of the file specified (may be relative to
> +.BR getcwd (3)
> +of the caller) as the first argument of
> .BR execve (),
I find the "(may be relative...)" piece confusing.
It's simpler just to s/absolute pathname/pathname/, and that's the
change I made.
> and
> .I arg...
> @@ -356,6 +358,11 @@ argument of
> .BR execve (),
> starting at
> .IR argv[1] .
> +The absolute pathname of the script is also available
> +in the same auxiliary vector the environment and argument variables are in, as
> +.BR AT_EXECFN .
> +See
> +.BR getauxval (3).
> Note that there is no way to get the
> .IR argv[0]
> that was passed to the
I applied the patch below.
Cheers,
Michael
diff --git a/man2/execve.2 b/man2/execve.2
index 435a6b363..4eaf1967e 100644
--- a/man2/execve.2
+++ b/man2/execve.2
@@ -346,7 +346,7 @@ will be invoked with the following arguments:
.PP
where
.I pathname
-is the absolute pathname of the file specified as the first argument of
+is the pathname of the file specified as the first argument of
.BR execve (),
and
.I arg...
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
