ARM: 7748/1: oabi: handle faults when loading swi instruction from userspace

[cascardo/linux.git] / arch / arm / kernel / entry-common.S

diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index bc5bc0a..4bc816a 100644 (file)
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -362,6 +362,16 @@ ENTRY(vector_swi)
        str     r0, [sp, #S_OLD_R0]             @ Save OLD_R0
        zero_fp
 
+#ifdef CONFIG_ALIGNMENT_TRAP
+       ldr     ip, __cr_alignment
+       ldr     ip, [ip]
+       mcr     p15, 0, ip, c1, c0              @ update control register
+#endif
+
+       enable_irq
+       ct_user_exit
+       get_thread_info tsk
+
        /*
         * Get the system call number.
         */
@@ -375,9 +385,9 @@ 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 +402,13 @@ 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
+ USER( 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
-#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 +443,21 @@ 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 failed to handle a fault trying to access the page
+        * containing the swi instruction, but we're not really in a
+        * position to return -EFAULT. Instead, return back to the
+        * instruction and re-enter the user fault handling path trying
+        * to page it in. This will likely result in sending SEGV to the
+        * current task.
+        */
+9001:
+       sub     lr, lr, #4
+       str     lr, [sp, #S_PC]
+       b       ret_fast_syscall
+#endif
 ENDPROC(vector_swi)
 
        /*