diff mbox

??: A bug about system call on ARM

Message ID ih0015wu30o5nq4ajf437rl7.1369916575726@email.android.com (mailing list archive)
State New, archived
Headers show

Commit Message

Wang, Yalin May 30, 2013, 12:22 p.m. UTC 
Hi Will,

i see your solution,
i Will test it tomorrow,
and report the result to you ASAP!

Thank for your help very much.

Sent from Moxier Mail
(http://www.moxier.com)


----- ???? -----
???: Will Deacon <will.deacon@arm.com>
???: "Wang, Yalin" <Yalin.Wang@sonymobile.com>
??: 'richard -rw- weinberger' <richard.weinberger@gmail.com>, "'linux-arch@vger.kernel.org'" <linux-arch@vger.kernel.org>, "'linux-kernel@vger.kernel.org'" <linux-kernel@vger.kernel.org>, "'linux-arm-kernel@lists.infradead.org'" <linux-arm-kernel@lists.infradead.org>
????: 2013-5-30 19:41
??: Re: A bug about system call on ARM



On Thu, May 30, 2013 at 10:09:49AM +0100, Will Deacon wrote:
> On Thu, May 30, 2013 at 02:41:42AM +0100, Wang, Yalin wrote:

> > If you have some patch for this issue,

> > I can do the test for it .

>

> I'll have a look at cooking something which uses an exception table entry

> to rewind the PC and retry the system call. That's simpler than directly

> injecting a user page fault from the system call path.


Ok, please can you try the following?

Will

--->8

Comments

Nicolas Pitre May 31, 2013, 4:03 a.m. UTC | #1 
On Thu, 30 May 2013, Wang, Yalin wrote:

> Hi Will,
> 
> i see your solution,
> i Will test it tomorrow,
> and report the result to you ASAP!

This is good if you can report success without changing any of your 
current configuration.  This issue is worth fixing.

However, as others have mentioned already, you most likely can set 
CONFIG_OABI_COMPAT to n afterwards.  Not only will this make you immune 
to the bug you reported, but that will also make the syscall path more 
efficient as well.


Nicolas
diff mbox

Patch

diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index bc5bc0a..855926e 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -361,6 +361,15 @@  ENTRY(vector_swi)
        str     r8, [sp, #S_PSR]                @ Save CPSR
        str     r0, [sp, #S_OLD_R0]             @ Save OLD_R0
        zero_fp
+       enable_irq
+       ct_user_exit
+
+#ifdef CONFIG_ALIGNMENT_TRAP
+       ldr     ip, __cr_alignment
+       ldr     ip, [ip]
+       mcr     p15, 0, ip, c1, c0              @ update control register
+#endif
+       get_thread_info tsk

        /*
         * Get the system call number.
@@ -375,9 +384,9 @@  ENTRY(vector_swi)
 #ifdef CONFIG_ARM_THUMB
        tst     r8, #PSR_T_BIT
        movne   r10, #0                         @ no thumb OABI emulation
-       ldreq   r10, [lr, #-4]                  @ get SWI instruction
+ USER( ldreq   r10, [lr, #-4]          )       @ get SWI instruction
 #else
-       ldr     r10, [lr, #-4]                  @ get SWI instruction
+ USER( ldr     r10, [lr, #-4]          )       @ get SWI instruction
 #endif
 #ifdef CONFIG_CPU_ENDIAN_BE8
        rev     r10, r10                        @ little endian instruction
@@ -392,22 +401,13 @@  ENTRY(vector_swi)
        /* Legacy ABI only, possibly thumb mode. */
        tst     r8, #PSR_T_BIT                  @ this is SPSR from save_user_regs
        addne   scno, r7, #__NR_SYSCALL_BASE    @ put OS number in
-       ldreq   scno, [lr, #-4]
+ USER( ldreq   scno, [lr, #-4]         )

 #else
        /* Legacy ABI only. */
-       ldr     scno, [lr, #-4]                 @ get SWI instruction
-#endif
-
-#ifdef CONFIG_ALIGNMENT_TRAP
-       ldr     ip, __cr_alignment
-       ldr     ip, [ip]
-       mcr     p15, 0, ip, c1, c0              @ update control register
+ USER( ldr     scno, [lr, #-4]         )       @ get SWI instruction
 #endif
-       enable_irq
-       ct_user_exit

-       get_thread_info tsk
        adr     tbl, sys_call_table             @ load syscall table pointer

 #if defined(CONFIG_OABI_COMPAT)
@@ -442,6 +442,18 @@  local_restart:
        eor     r0, scno, #__NR_SYSCALL_BASE    @ put OS number back
        bcs     arm_syscall
        b       sys_ni_syscall                  @ not private func
+
+#if defined(CONFIG_OABI_COMPAT) || !defined(CONFIG_AEABI)
+       /*
+        * We may have faulted trying to load the SWI instruction due to
+        * concurrent page aging on another CPU. In this case, return
+        * back to the swi instruction and fault the page back.
+        */
+9001:
+       sub     lr, lr, #4
+       str     lr, [sp, #S_PC]
+       b       ret_fast_syscall
+#endif
 ENDPROC(vector_swi)

        /*