misc: Add internal __getauxval2 function
Commit Message
The explicit error return value (without in-band signaling) avoids
complicated steps to detect errors based on whether errno has been
updated.
Tested on x86_64-linux-gnu.
---
include/sys/auxv.h | 5 +++++
misc/getauxval.c | 33 +++++++++++++++++++++++++++------
2 files changed, 32 insertions(+), 6 deletions(-)
Comments
On Tue, Oct 27, 2020 at 2:43 AM Florian Weimer via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> The explicit error return value (without in-band signaling) avoids
> complicated steps to detect errors based on whether errno has been
> updated.
>
> Tested on x86_64-linux-gnu.
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Alistair
>
> ---
> include/sys/auxv.h | 5 +++++
> misc/getauxval.c | 33 +++++++++++++++++++++++++++------
> 2 files changed, 32 insertions(+), 6 deletions(-)
>
> diff --git a/include/sys/auxv.h b/include/sys/auxv.h
> index 3bab6d05d4..dd0602b08d 100644
> --- a/include/sys/auxv.h
> +++ b/include/sys/auxv.h
> @@ -5,4 +5,9 @@
> extern __typeof (getauxval) __getauxval;
> libc_hidden_proto (__getauxval)
>
> +/* Like getauxval, but writes the value to *RESULT and returns true if
> + found, or returns false. Does not set errno. */
> +_Bool __getauxval2 (unsigned long int type, unsigned long int *result);
> +libc_hidden_proto (__getauxval2)
> +
> #endif /* !_ISOMAC */
> diff --git a/misc/getauxval.c b/misc/getauxval.c
> index d7f9f957d0..e96d4dfa20 100644
> --- a/misc/getauxval.c
> +++ b/misc/getauxval.c
> @@ -18,26 +18,47 @@
> #include <sys/auxv.h>
> #include <errno.h>
> #include <ldsodefs.h>
> +#include <stdbool.h>
>
> -
> -unsigned long int
> -__getauxval (unsigned long int type)
> +bool
> +__getauxval2 (unsigned long int type, unsigned long int *result)
> {
> #ifdef HAVE_AUX_VECTOR
> ElfW(auxv_t) *p;
> #endif
>
> if (type == AT_HWCAP)
> - return GLRO(dl_hwcap);
> + {
> + *result = GLRO(dl_hwcap);
> + return true;
> + }
> else if (type == AT_HWCAP2)
> - return GLRO(dl_hwcap2);
> + {
> + *result = GLRO(dl_hwcap2);
> + return true;
> + }
>
> #ifdef HAVE_AUX_VECTOR
> for (p = GLRO(dl_auxv); p->a_type != AT_NULL; p++)
> if (p->a_type == type)
> - return p->a_un.a_val;
> + {
> + *result = p->a_un.a_val;
> + return true;
> + }
> #endif
>
> + return false;
> +}
> +libc_hidden_def (__getauxval2)
> +
> +unsigned long int
> +__getauxval (unsigned long int type)
> +{
> + unsigned long int result;
> +
> + if (__getauxval2 (type, &result))
> + return result;
> +
> __set_errno (ENOENT);
> return 0;
> }
>
> --
> Red Hat GmbH, https://de.redhat.com/ , Registered seat: Grasbrunn,
> Commercial register: Amtsgericht Muenchen, HRB 153243,
> Managing Directors: Charles Cachera, Brian Klemm, Laurie Krebs, Michael O'Neill
>
@@ -5,4 +5,9 @@
extern __typeof (getauxval) __getauxval;
libc_hidden_proto (__getauxval)
+/* Like getauxval, but writes the value to *RESULT and returns true if
+ found, or returns false. Does not set errno. */
+_Bool __getauxval2 (unsigned long int type, unsigned long int *result);
+libc_hidden_proto (__getauxval2)
+
#endif /* !_ISOMAC */
@@ -18,26 +18,47 @@
#include <sys/auxv.h>
#include <errno.h>
#include <ldsodefs.h>
+#include <stdbool.h>
-
-unsigned long int
-__getauxval (unsigned long int type)
+bool
+__getauxval2 (unsigned long int type, unsigned long int *result)
{
#ifdef HAVE_AUX_VECTOR
ElfW(auxv_t) *p;
#endif
if (type == AT_HWCAP)
- return GLRO(dl_hwcap);
+ {
+ *result = GLRO(dl_hwcap);
+ return true;
+ }
else if (type == AT_HWCAP2)
- return GLRO(dl_hwcap2);
+ {
+ *result = GLRO(dl_hwcap2);
+ return true;
+ }
#ifdef HAVE_AUX_VECTOR
for (p = GLRO(dl_auxv); p->a_type != AT_NULL; p++)
if (p->a_type == type)
- return p->a_un.a_val;
+ {
+ *result = p->a_un.a_val;
+ return true;
+ }
#endif
+ return false;
+}
+libc_hidden_def (__getauxval2)
+
+unsigned long int
+__getauxval (unsigned long int type)
+{
+ unsigned long int result;
+
+ if (__getauxval2 (type, &result))
+ return result;
+
__set_errno (ENOENT);
return 0;
}