Re: [Qemu-devel] [PATCH v2 1/2] util: Introduce qemu_get_pid_name

["Daniel P. Berrange" <berrange@redhat.com>]

On Wed, Sep 21, 2016 at 01:26:02PM +0200, Michal Privoznik wrote:
> This is a small helper that tries to fetch binary name for given
> PID.
> 
> Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
> ---
>  include/qemu/osdep.h | 10 ++++++++++
>  util/oslib-posix.c   | 37 +++++++++++++++++++++++++++++++++++++
>  util/oslib-win32.c   |  7 +++++++
>  3 files changed, 54 insertions(+)
> 
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 9e9fa61..384bfe2 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -388,6 +388,16 @@ void os_mem_prealloc(int fd, char *area, size_t sz, Error **errp);
>  int qemu_read_password(char *buf, int buf_size);
>  
>  /**
> + * qemu_get_pid_name:
> + * @pid: pid of a process
> + *
> + * For given @pid fetch its name. Caller is responsible for
> + * freeing the string when no longer needed.
> + * Returns allocated string on success, NULL on failure.
> + */
> +char *qemu_get_pid_name(pid_t pid);
> +
> +/**
>   * qemu_fork:
>   *
>   * A version of fork that avoids signal handler race
> diff --git a/util/oslib-posix.c b/util/oslib-posix.c
> index f2d4e9e..0555425 100644
> --- a/util/oslib-posix.c
> +++ b/util/oslib-posix.c
> @@ -46,6 +46,7 @@
>  
>  #ifdef __FreeBSD__
>  #include <sys/sysctl.h>
> +#include <libutil.h>
>  #endif
>  
>  #include "qemu/mmap-alloc.h"
> @@ -430,6 +431,42 @@ int qemu_read_password(char *buf, int buf_size)
>  }
>  
>  
> +char *qemu_get_pid_name(pid_t pid)
> +{
> +    char *name = NULL;
> +    char *pid_path;
> +    char buf[PATH_MAX];
> +    size_t len;
> +
> +#if defined(__FreeBSD__)
> +    /* BSDs don't have /proc, but they provide a nice substitute */
> +    struct kinfo_proc *proc = kinfo_getproc(pid);
> +    if (proc) {
> +        name = g_strdup(proc->ki_comm);
> +        free(proc);
> +    }
> +#else
> +    /* Assume a system with reasonable procfs */
> +    FILE *f;
> +
> +    pid_path = g_strdup_printf("/proc/%d/cmdline", pid);
> +    f = fopen(pid_path, "r");
> +    if (!f) {
> +        return NULL;
> +    }
> +
> +    len = fread(buf, 1, sizeof(buf), f);
> +    if (len) {
> +        name = g_strdup(buf);
> +    }
> +    fclose(f);

This use of fixed length buffer and the calling of multiple stdio
functions can be replaced by g_file_get_contents() which will be
much clearer.


Regards,
Daniel
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