From: Florian Weimer <fweimer@redhat.com>
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Cc: libc-alpha@sourceware.org,
Luca Boccassi <luca.boccassi@gmail.com>,
Philip Withnall <bugzilla@tecnocode.co.uk>
Subject: Re: [PATCH v4 3/3] linux: Add pidfd_getpid
Date: Mon, 22 May 2023 15:00:13 +0200 [thread overview]
Message-ID: <87h6s44j36.fsf@oldenburg3.str.redhat.com> (raw)
In-Reply-To: <20230517173516.1988283-4-adhemerval.zanella@linaro.org> (Adhemerval Zanella's message of "Wed, 17 May 2023 14:35:16 -0300")
* Adhemerval Zanella:
> This interface allows to obtain the associated pid ID from the
“process ID”
> process file descriptor. It is done by parsing the procps fdinfo
> information. Its prototype is:
>
> pid_t pidfd_getpid (int fd)
>
> It returns the associated pid or -1 in case of an error and set the
> errno accordingly. The possible errno values are the smae from
Typos: “and set[s] [] errno accordingly.”
“are [those] from”
> open, read, and close (used on procps parsing), along with:
>
> - EINVAL if the FP is negative (similar to fexecve).
>
> - EBADF if the FD does not have a PID associated of if the fdinfo
“associated o[r] if”
> fields contains a value larger than pid_t.
>
> - EREMOTE if the PID is in a separate namespace.
>
> - ESRCH if the process is already terminated.
> diff --git a/sysdeps/unix/sysv/linux/pidfd_getpid.c b/sysdeps/unix/sysv/linux/pidfd_getpid.c
> new file mode 100644
> index 0000000000..ae5fa100eb
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/pidfd_getpid.c
> @@ -0,0 +1,122 @@
> +pid_t
> +pidfd_getpid (int fd)
> +{
> + if (__glibc_unlikely (fd < 0))
> + {
> + __set_errno (EINVAL);
> + return -1;
> + }
> +
> + char fdinfoname[FDINFO_FILENAME_LEN];
> +
> + char *p = mempcpy (fdinfoname, FDINFO_TO_FILENAME_PREFIX,
> + strlen (FDINFO_TO_FILENAME_PREFIX));
> + *_fitoa_word (fd, p, 10, 0) = '\0';
> +
> + struct parse_fdinfo_t fdinfo = { .found = false, .pid = -1 };
> + if (procutils_read_file (fdinfoname, parse_fdinfo, &fdinfo) == -1)
> + /* The fdinfo contains an invalid 'Pid:' value. */
> + return INLINE_SYSCALL_ERROR_RETURN_VALUE (EBADF);
> +
> + /* The FD does not have a 'Pid:' entry associated. */
> + if (!fdinfo.found)
> + return INLINE_SYSCALL_ERROR_RETURN_VALUE (EBADF);
> +
> + /* The pidfd cannot be resolved because it is in a separate pid
> + namespace. */
> + if (fdinfo.pid == 0)
> + return INLINE_SYSCALL_ERROR_RETURN_VALUE (EREMOTE);
> +
> + /* A negative value means the process is terminated. */
> + if (fdinfo.pid < 0)
> + return INLINE_SYSCALL_ERROR_RETURN_VALUE (ESRCH);
> +
> + return fdinfo.pid;
We are making a ot of error codes here. How likely is it that they
match what a future ioctl will do?
> diff --git a/sysdeps/unix/sysv/linux/tst-pidfd.c b/sysdeps/unix/sysv/linux/tst-pidfd.c
> index 64d8a2ef40..a03de4b290 100644
> --- a/sysdeps/unix/sysv/linux/tst-pidfd.c
> +++ b/sysdeps/unix/sysv/linux/tst-pidfd.c
> + /* Check if pidfd_getpid returns ESRCH for exited subprocess. */
> + {
> + int pidfd = pidfd_fork (0);
> + if (pidfd == 0)
> + exit (EXIT_SUCCESS);
Should be _exit, so that the atexit handlers do not run.
I think the main remaining question is errno alignment with a future
direct kernel interface for this.
Thanks,
Florian
next prev parent reply other threads:[~2023-05-22 13:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-17 17:35 [PATCH v4 0/3] Add pidfd_spawn, pidfd_spawnp, pidfd_fork, and pidfd_getpid Adhemerval Zanella
2023-05-17 17:35 ` [PATCH v4 1/3] posix: Add pidfd_spawn and pidfd_spawnp (BZ# 30349) Adhemerval Zanella
2023-05-22 10:41 ` Florian Weimer
2023-05-22 10:46 ` Andreas Schwab
2023-05-22 14:18 ` Adhemerval Zanella Netto
2023-05-17 17:35 ` [PATCH v4 2/3] posix: Add pidfd_fork Adhemerval Zanella
2023-05-22 10:12 ` Florian Weimer
2023-05-22 12:44 ` Christian Brauner
2023-05-22 14:48 ` Adhemerval Zanella Netto
2023-05-17 17:35 ` [PATCH v4 3/3] linux: Add pidfd_getpid Adhemerval Zanella
2023-05-22 13:00 ` Florian Weimer [this message]
2023-05-22 17:13 ` Adhemerval Zanella Netto
2023-05-22 13:53 ` Joe Simmons-Talbott
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