diff mbox

[07/15] Use semget syscall for Linux implementation

Message ID 1478010323-13076-8-git-send-email-adhemerval.zanella@linaro.org
State Dropped
Headers

Commit Message

Adhemerval Zanella Nov. 1, 2016, 2:25 p.m. UTC 
  This patch add a direct call to semget syscall if it is defined by
kernel headers.

hecked on x86_64, i686, powerpc64le, aarch64, and armhf.

	* sysdeps/unix/sysv/linux/semget.c (semget): Use semget syscall
	if it is defined.
---
 ChangeLog                        |  3 +++
 sysdeps/unix/sysv/linux/semget.c | 11 ++++++-----
 2 files changed, 9 insertions(+), 5 deletions(-)

Comments

Andreas Schwab Nov. 1, 2016, 3:34 p.m. UTC | #1 
On Nov 01 2016, Adhemerval Zanella <adhemerval.zanella@linaro.org> wrote:

> This patch add a direct call to semget syscall if it is defined by
> kernel headers.

That does not mean that the running kernel provides it.

Andreas.
Joseph Myers Nov. 1, 2016, 4:40 p.m. UTC | #2 
On Tue, 1 Nov 2016, Andreas Schwab wrote:

> On Nov 01 2016, Adhemerval Zanella <adhemerval.zanella@linaro.org> wrote:
> 
> > This patch add a direct call to semget syscall if it is defined by
> > kernel headers.
> 
> That does not mean that the running kernel provides it.

Specifically, this sort of patch series needs to be accompanied by an 
analysis of when the relevant syscalls were added for each supported 
architecture (and subarchitecture for cases with multiple syscall tables 
for different ABNs).  If present (in the syscall table as well as in 
asm/unistd.h) in the minimum kernel version, OK, otherwise you need 
appropriate __ASSUME_* conditionals (even if not present in the latest 
kernel, it might be added in future, so you should have those conditionals 
now to avoid breaking things when current glibc is compiled with future 
kernel headers).
Adhemerval Zanella Nov. 1, 2016, 5:16 p.m. UTC | #3 
On 01/11/2016 14:40, Joseph Myers wrote:
> On Tue, 1 Nov 2016, Andreas Schwab wrote:
> 
>> On Nov 01 2016, Adhemerval Zanella <adhemerval.zanella@linaro.org> wrote:
>>
>>> This patch add a direct call to semget syscall if it is defined by
>>> kernel headers.
>>
>> That does not mean that the running kernel provides it.
> 
> Specifically, this sort of patch series needs to be accompanied by an 
> analysis of when the relevant syscalls were added for each supported 
> architecture (and subarchitecture for cases with multiple syscall tables 
> for different ABNs).  If present (in the syscall table as well as in 
> asm/unistd.h) in the minimum kernel version, OK, otherwise you need 
> appropriate __ASSUME_* conditionals (even if not present in the latest 
> kernel, it might be added in future, so you should have those conditionals 
> now to avoid breaking things when current glibc is compiled with future 
> kernel headers).

Indeed, I did not consider the case of latest kernel headers.  Based
on current Linux approach and historical implementation for sysv IPC
I think we can assume that either the kernel only supports the old
'ipc' syscall or all the sysvipc syscall wire-up.  Do you know if we
do require an __ASSUME for each syscall?
Zack Weinberg Nov. 1, 2016, 5:27 p.m. UTC | #4 
On Tue, Nov 1, 2016 at 1:16 PM, Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
> On 01/11/2016 14:40, Joseph Myers wrote:
>> On Tue, 1 Nov 2016, Andreas Schwab wrote:
>>
>>> On Nov 01 2016, Adhemerval Zanella <adhemerval.zanella@linaro.org> wrote:
>>>
>>>> This patch add a direct call to semget syscall if it is defined by
>>>> kernel headers.
>>>
>>> That does not mean that the running kernel provides it.
>>
>> Specifically, this sort of patch series needs to be accompanied by an
>> analysis of when the relevant syscalls were added for each supported
>> architecture (and subarchitecture for cases with multiple syscall tables
>> for different ABNs).  If present (in the syscall table as well as in
>> asm/unistd.h) in the minimum kernel version, OK, otherwise you need
>> appropriate __ASSUME_* conditionals (even if not present in the latest
>> kernel, it might be added in future, so you should have those conditionals
>> now to avoid breaking things when current glibc is compiled with future
>> kernel headers).
>
> Indeed, I did not consider the case of latest kernel headers.  Based
> on current Linux approach and historical implementation for sysv IPC
> I think we can assume that either the kernel only supports the old
> 'ipc' syscall or all the sysvipc syscall wire-up.  Do you know if we
> do require an __ASSUME for each syscall?

It wouldn't have made sense to add direct syscalls for some but not
all of the APIs that were multiplexed, so I would think one __ASSUME
is enough.

zw
Joseph Myers Nov. 1, 2016, 5:35 p.m. UTC | #5 
On Tue, 1 Nov 2016, Adhemerval Zanella wrote:

> Indeed, I did not consider the case of latest kernel headers.  Based
> on current Linux approach and historical implementation for sysv IPC
> I think we can assume that either the kernel only supports the old
> 'ipc' syscall or all the sysvipc syscall wire-up.  Do you know if we
> do require an __ASSUME for each syscall?

If your analysis shows that all the syscalls were always wired up (in both 
places, syscall table and asm/unistd.h) at the same time, you can just use 
a single __ASSUME (or if by mistake some architectures were only partially 
wired up, you could still use a single __ASSUME if it's conservatively 
safe).
diff mbox

Patch

diff --git a/sysdeps/unix/sysv/linux/semget.c b/sysdeps/unix/sysv/linux/semget.c
index 52189fd..739346b 100644
--- a/sysdeps/unix/sysv/linux/semget.c
+++ b/sysdeps/unix/sysv/linux/semget.c
@@ -16,13 +16,10 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <errno.h>
 #include <sys/sem.h>
 #include <ipc_priv.h>
-#include <stdlib.h>		/* for definition of NULL */
-
 #include <sysdep.h>
-#include <sys/syscall.h>
+#include <errno.h>
 
 /* Return identifier for array of NSEMS semaphores associated with
    KEY.  */
@@ -30,5 +27,9 @@ 
 int
 semget (key_t key, int nsems, int semflg)
 {
-  return INLINE_SYSCALL (ipc, 5, IPCOP_semget, key, nsems, semflg, NULL);
+#ifdef __NR_semget
+  return INLINE_SYSCALL_CALL (semget, key, nsems, semflg);
+#else
+  return INLINE_SYSCALL_CALL (ipc, IPCOP_semget, key, nsems, semflg, NULL);
+#endif
 }