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[2/4] Consolidate off_t/off64_t syscall argument passing

Message ID 1456431555-14182-3-git-send-email-adhemerval.zanella@linaro.org
State New
Headers show

Commit Message

Adhemerval Zanella Netto Feb. 25, 2016, 8:19 p.m. UTC
From: Adhemerval Zanella <adhemerval.zanella@linaro.com>

This patch add three new macros (SYSCALL_LL, SYSCALL_LL64, and
__ASSUME_WORDSIZE64_ILP32) to use along with off_t and off64_t argument
syscalls.  The rationale for this change is:

1. Remove multiple implementations for the same syscall for different
   architectures (for instance, pread have 6 different implementations).

2. Also remove the requirement to use syscall wrappers for cancellable
   entrypoints.

The macro usage should be used along __ALIGNMENT_ARG to follow ABI constrains
for architecture where it applies.  For instance, pread can be rewritten as:

  return SYSCALL_CANCEL (pread, fd, buf, count,
                         __ALIGNMENT_ARG SYSCALL_LL (offset));

Another macro, SYSCALL_LL64, is provided for off64_t.  The macro
__ASSUME_WORDSIZE64_ILP32 is used by the ABI to define is uses 64-bit register
even if ABI is ILP32 (for instance x32 and mips64-n32).

The changes itself are not currently used in any implementation, so no
code change is expected.

	* sysdeps/unix/sysv/linux/generic/sysdep.h (__ALIGNMENT_ARG): Move
	definition.
	(__ALIGNMENT_COUNT): Likewise.
	* sysdeps/unix/sysv/linux/sysdep.h (__ALIGNMENT_ARG): To here.
	(__ALIGNMENT_COUNT): Likewise.
	(SYSCALL_LL): New define.
	(SYSCALL_LL64): Likewise.
	* sysdeps/unix/sysv/linux/mips/kernel-features.h:
	[_MIPS_SIM == _ABIO32] (__ASSUME_WORDSIZE64_ILP32): Define.
	* sysdeps/unix/sysv/linux/x86_64/kernel-features.h:
	[ILP32] (__ASUME_WORDSIZE64_ILP32): Likewise.
---
 sysdeps/unix/sysv/linux/generic/sysdep.h         | 10 ----------
 sysdeps/unix/sysv/linux/mips/kernel-features.h   |  6 ++++++
 sysdeps/unix/sysv/linux/sysdep.h                 | 23 +++++++++++++++++++++++
 sysdeps/unix/sysv/linux/x86_64/kernel-features.h |  6 ++++++
 5 files changed, 47 insertions(+), 10 deletions(-)

Comments

Mike Frysinger April 10, 2016, 4:14 a.m. UTC | #1
On 25 Feb 2016 17:19, Adhemerval Zanella wrote:
> --- a/sysdeps/unix/sysv/linux/sysdep.h
> +++ b/sysdeps/unix/sysv/linux/sysdep.h
>
> +/* Provide a dummy argument that can be used to force register
> +   alignment for register pairs if required by the syscall ABI.  */
> +#ifdef __ASSUME_ALIGNED_REGISTER_PAIRS
> +#define __ALIGNMENT_ARG 0,
> +#define __ALIGNMENT_COUNT(a,b) b
> +#else
> +#define __ALIGNMENT_ARG
> +#define __ALIGNMENT_COUNT(a,b) a
> +#endif

while not a new issue, should the return be parenthesized ?
i.e. (b) and (a) ?
-mike
Adhemerval Zanella Netto April 11, 2016, 12:17 p.m. UTC | #2
On 10-04-2016 01:14, Mike Frysinger wrote:
> On 25 Feb 2016 17:19, Adhemerval Zanella wrote:
>> --- a/sysdeps/unix/sysv/linux/sysdep.h
>> +++ b/sysdeps/unix/sysv/linux/sysdep.h
>>
>> +/* Provide a dummy argument that can be used to force register
>> +   alignment for register pairs if required by the syscall ABI.  */
>> +#ifdef __ASSUME_ALIGNED_REGISTER_PAIRS
>> +#define __ALIGNMENT_ARG 0,
>> +#define __ALIGNMENT_COUNT(a,b) b
>> +#else
>> +#define __ALIGNMENT_ARG
>> +#define __ALIGNMENT_COUNT(a,b) a
>> +#endif
> 
> while not a new issue, should the return be parenthesized ?
> i.e. (b) and (a) ?
> -mike
> 

I will change that, thanks.
Adhemerval Zanella Netto April 11, 2016, 1:07 p.m. UTC | #3
On 11-04-2016 09:17, Adhemerval Zanella wrote:
> 
> 
> On 10-04-2016 01:14, Mike Frysinger wrote:
>> On 25 Feb 2016 17:19, Adhemerval Zanella wrote:
>>> --- a/sysdeps/unix/sysv/linux/sysdep.h
>>> +++ b/sysdeps/unix/sysv/linux/sysdep.h
>>>
>>> +/* Provide a dummy argument that can be used to force register
>>> +   alignment for register pairs if required by the syscall ABI.  */
>>> +#ifdef __ASSUME_ALIGNED_REGISTER_PAIRS
>>> +#define __ALIGNMENT_ARG 0,
>>> +#define __ALIGNMENT_COUNT(a,b) b
>>> +#else
>>> +#define __ALIGNMENT_ARG
>>> +#define __ALIGNMENT_COUNT(a,b) a
>>> +#endif
>>
>> while not a new issue, should the return be parenthesized ?
>> i.e. (b) and (a) ?
>> -mike
>>
> 
> I will change that, thanks.

In fact we can not change it: some functions uses the define as
__ALIGNMENT_COUNT (3, 4) and some ports uses to correct select
the LOAD_ARGS_{3,4} in syscall generation (nios2).  Using 
parenthesis leads it to evaluate as LOAD_ARGS_(3) and this
issuing a build issue (this can be fixed I think, but it is
not the idea of this patch).
diff mbox

Patch

diff --git a/sysdeps/unix/sysv/linux/generic/sysdep.h b/sysdeps/unix/sysv/linux/generic/sysdep.h
index 4f2c65d..b0422ff 100644
--- a/sysdeps/unix/sysv/linux/generic/sysdep.h
+++ b/sysdeps/unix/sysv/linux/generic/sysdep.h
@@ -31,13 +31,3 @@ 
 #define __NR_pread __NR_pread64
 #define __NR_pwrite __NR_pwrite64
 #endif
-
-/* Provide a dummy argument that can be used to force register
-   alignment for register pairs if required by the syscall ABI.  */
-#ifdef __ASSUME_ALIGNED_REGISTER_PAIRS
-#define __ALIGNMENT_ARG 0,
-#define __ALIGNMENT_COUNT(a,b) b
-#else
-#define __ALIGNMENT_ARG
-#define __ALIGNMENT_COUNT(a,b) a
-#endif
diff --git a/sysdeps/unix/sysv/linux/mips/kernel-features.h b/sysdeps/unix/sysv/linux/mips/kernel-features.h
index ea6a914..17ab696 100644
--- a/sysdeps/unix/sysv/linux/mips/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/mips/kernel-features.h
@@ -53,3 +53,9 @@ 
 #if _MIPS_SIM == _ABIO32
 # define __ASSUME_ALIGNED_REGISTER_PAIRS	1
 #endif
+
+/* Define that mips64-n32 is a ILP32 ABI to set the correct interface to
+   pass 64-bits values through syscalls.  */
+#if _MIPS_SIM == _ABIN32
+# define __ASSUME_WORDSIZE64_ILP32	1
+#endif
diff --git a/sysdeps/unix/sysv/linux/sysdep.h b/sysdeps/unix/sysv/linux/sysdep.h
index c98fc3a..5ee73d5 100644
--- a/sysdeps/unix/sysv/linux/sysdep.h
+++ b/sysdeps/unix/sysv/linux/sysdep.h
@@ -15,6 +15,8 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#include <bits/wordsize.h>
+
 /* Set error number and return -1.  A target may choose to return the
    internal function, __syscall_error, which sets errno and returns -1.
    We use -1l, instead of -1, so that it can be casted to (void *).  */
@@ -23,3 +25,24 @@ 
     __set_errno (err);				\
     -1l;					\
   })
+
+/* Provide a dummy argument that can be used to force register
+   alignment for register pairs if required by the syscall ABI.  */
+#ifdef __ASSUME_ALIGNED_REGISTER_PAIRS
+#define __ALIGNMENT_ARG 0,
+#define __ALIGNMENT_COUNT(a,b) b
+#else
+#define __ALIGNMENT_ARG
+#define __ALIGNMENT_COUNT(a,b) a
+#endif
+
+/* Provide a common macro to pass 64-bit value on syscalls.  */
+#if __WORDSIZE == 64 || defined __ASSUME_WORDSIZE64_ILP32
+# define SYSCALL_LL(val)   (val)
+# define SYSCALL_LL64(val) (val)
+#else
+#define SYSCALL_LL(val)   \
+  __LONG_LONG_PAIR ((val) >> 31, __val)
+#define SYSCALL_LL64(val) \
+  __LONG_LONG_PAIR ((long) ((val) >> 32), (long) ((val) & 0xffffffff))
+#endif
diff --git a/sysdeps/unix/sysv/linux/x86_64/kernel-features.h b/sysdeps/unix/sysv/linux/x86_64/kernel-features.h
index 0b84f11..569e8f8 100644
--- a/sysdeps/unix/sysv/linux/x86_64/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/x86_64/kernel-features.h
@@ -35,4 +35,10 @@ 
 # define __ASSUME_GETCPU_SYSCALL	1
 #endif
 
+/* Define that x32 is a ILP32 ABI to set the correct interface to pass
+   64-bits values through syscalls.  */
+#ifdef __ILP32__
+# define __ASSUME_WORDSIZE64_ILP32	1
+#endif
+
 #include_next <kernel-features.h>