ARM: entry: rejig register allocation in exception entry handlers

This allows us to avoid moving registers twice to work around the
clobbered registers when we add calls to trace_hardirqs_{on,off}.

Ensure that all SVC handlers return with SPSR in r5 for consistency.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 43 insertions, 38 deletions

diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index fd42e667a81..582bb231044 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -45,7 +45,7 @@
         .endm
 
         .macro  pabt_helper
-        mov     r0, r2                  @ pass address of aborted instruction.
+        mov     r0, r4                  @ pass address of aborted instruction.
 #ifdef MULTI_PABORT
         ldr     ip, .LCprocfns
         mov     lr, pc
@@ -56,6 +56,8 @@
         .endm
 
         .macro  dabt_helper
+        mov     r2, r4
+        mov     r3, r5
 
         @
         @ Call the processor-specific abort handler:
@@ -157,26 +159,26 @@ ENDPROC(__und_invalid)
  SPFIX( subeq   sp, sp, #4      )
         stmia   sp, {r1 - r12}
 
-        ldmia   r0, {r1 - r3}
-        add     r5, sp, #S_SP - 4       @ here for interlock avoidance
-        mov     r4, #-1                 @  ""  ""      ""       ""
-        add     r0, sp, #(S_FRAME_SIZE + \stack_hole - 4)
- SPFIX( addeq   r0, r0, #4      )
-        str     r1, [sp, #-4]!          @ save the "real" r0 copied
+        ldmia   r0, {r3 - r5}
+        add     r7, sp, #S_SP - 4       @ here for interlock avoidance
+        mov     r6, #-1                 @  ""  ""      ""       ""
+        add     r2, sp, #(S_FRAME_SIZE + \stack_hole - 4)
+ SPFIX( addeq   r2, r2, #4      )
+        str     r3, [sp, #-4]!          @ save the "real" r0 copied
                                         @ from the exception stack
 
-        mov     r1, lr
+        mov     r3, lr
 
         @
         @ We are now ready to fill in the remaining blanks on the stack:
         @
-        @  r0 - sp_svc
-        @  r1 - lr_svc
-        @  r2 - lr_<exception>, already fixed up for correct return/restart
-        @  r3 - spsr_<exception>
-        @  r4 - orig_r0 (see pt_regs definition in ptrace.h)
+        @  r2 - sp_svc
+        @  r3 - lr_svc
+        @  r4 - lr_<exception>, already fixed up for correct return/restart
+        @  r5 - spsr_<exception>
+        @  r6 - orig_r0 (see pt_regs definition in ptrace.h)
         @
-        stmia   r5, {r0 - r4}
+        stmia   r7, {r2 - r6}
         .endm
 
         .align  5
@@ -187,7 +189,7 @@ __dabt_svc:
         @ get ready to re-enable interrupts if appropriate
         @
         mrs     r9, cpsr
-        tst     r3, #PSR_I_BIT
+        tst     r5, #PSR_I_BIT
         biceq   r9, r9, #PSR_I_BIT
 
         dabt_helper
@@ -208,8 +210,8 @@ __dabt_svc:
         @
         @ restore SPSR and restart the instruction
         @
-        ldr     r2, [sp, #S_PSR]
-        svc_exit r2                             @ return from exception
+        ldr     r5, [sp, #S_PSR]
+        svc_exit r5                             @ return from exception
  UNWIND(.fnend          )
 ENDPROC(__dabt_svc)
 
@@ -232,13 +234,13 @@ __irq_svc:
         tst     r0, #_TIF_NEED_RESCHED
         blne    svc_preempt
 #endif
-        ldr     r4, [sp, #S_PSR]                @ irqs are already disabled
+        ldr     r5, [sp, #S_PSR]
 #ifdef CONFIG_TRACE_IRQFLAGS
         @ The parent context IRQs must have been enabled to get here in
         @ the first place, so there's no point checking the PSR I bit.
         bl      trace_hardirqs_on
 #endif
-        svc_exit r4                             @ return from exception
+        svc_exit r5                             @ return from exception
  UNWIND(.fnend          )
 ENDPROC(__irq_svc)
 
@@ -273,15 +275,16 @@ __und_svc:
         @  r0 - instruction
         @
 #ifndef CONFIG_THUMB2_KERNEL
-        ldr     r0, [r2, #-4]
+        ldr     r0, [r4, #-4]
 #else
-        ldrh    r0, [r2, #-2]                   @ Thumb instruction at LR - 2
+        ldrh    r0, [r4, #-2]                   @ Thumb instruction at LR - 2
         and     r9, r0, #0xf800
         cmp     r9, #0xe800                     @ 32-bit instruction if xx >= 0
-        ldrhhs  r9, [r2]                        @ bottom 16 bits
+        ldrhhs  r9, [r4]                        @ bottom 16 bits
         orrhs   r0, r9, r0, lsl #16
 #endif
         adr     r9, BSYM(1f)
+        mov     r2, r4
         bl      call_fpe
 
         mov     r0, sp                          @ struct pt_regs *regs
@@ -295,8 +298,8 @@ __und_svc:
         @
         @ restore SPSR and restart the instruction
         @
-        ldr     r2, [sp, #S_PSR]                @ Get SVC cpsr
-        svc_exit r2                             @ return from exception
+        ldr     r5, [sp, #S_PSR]                @ Get SVC cpsr
+        svc_exit r5                             @ return from exception
  UNWIND(.fnend          )
 ENDPROC(__und_svc)
 
@@ -308,7 +311,7 @@ __pabt_svc:
         @ re-enable interrupts if appropriate
         @
         mrs     r9, cpsr
-        tst     r3, #PSR_I_BIT
+        tst     r5, #PSR_I_BIT
         biceq   r9, r9, #PSR_I_BIT
 
         pabt_helper
@@ -325,8 +328,8 @@ __pabt_svc:
         @
         @ restore SPSR and restart the instruction
         @
-        ldr     r2, [sp, #S_PSR]
-        svc_exit r2                             @ return from exception
+        ldr     r5, [sp, #S_PSR]
+        svc_exit r5                             @ return from exception
  UNWIND(.fnend          )
 ENDPROC(__pabt_svc)
 
@@ -357,23 +360,23 @@ ENDPROC(__pabt_svc)
  ARM(   stmib   sp, {r1 - r12}  )
  THUMB( stmia   sp, {r0 - r12}  )
 
-        ldmia   r0, {r1 - r3}
+        ldmia   r0, {r3 - r5}
         add     r0, sp, #S_PC           @ here for interlock avoidance
-        mov     r4, #-1                 @  ""  ""     ""        ""
+        mov     r6, #-1                 @  ""  ""     ""        ""
 
-        str     r1, [sp]                @ save the "real" r0 copied
+        str     r3, [sp]                @ save the "real" r0 copied
                                         @ from the exception stack
 
         @
         @ We are now ready to fill in the remaining blanks on the stack:
         @
-        @  r2 - lr_<exception>, already fixed up for correct return/restart
-        @  r3 - spsr_<exception>
-        @  r4 - orig_r0 (see pt_regs definition in ptrace.h)
+        @  r4 - lr_<exception>, already fixed up for correct return/restart
+        @  r5 - spsr_<exception>
+        @  r6 - orig_r0 (see pt_regs definition in ptrace.h)
         @
         @ Also, separately save sp_usr and lr_usr
         @
-        stmia   r0, {r2 - r4}
+        stmia   r0, {r4 - r6}
  ARM(   stmdb   r0, {sp, lr}^                   )
  THUMB( store_user_sp_lr r0, r1, S_SP - S_PC    )
 
@@ -397,7 +400,7 @@ ENDPROC(__pabt_svc)
         @ if it was interrupted in a critical region.  Here we
         @ perform a quick test inline since it should be false
         @ 99.9999% of the time.  The rest is done out of line.
-        cmp     r2, #TASK_SIZE
+        cmp     r4, #TASK_SIZE
         blhs    kuser_cmpxchg_fixup
 #endif
 #endif
@@ -441,6 +444,8 @@ ENDPROC(__irq_usr)
         .align  5
 __und_usr:
         usr_entry
+        mov     r2, r4
+        mov     r3, r5
 
         @
         @ fall through to the emulation code, which returns using r9 if
@@ -894,13 +899,13 @@ __kuser_cmpxchg:				@ 0xffff0fc0
         .text
 kuser_cmpxchg_fixup:
         @ Called from kuser_cmpxchg_check macro.
-        @ r2 = address of interrupted insn (must be preserved).
+        @ r4 = address of interrupted insn (must be preserved).
         @ sp = saved regs. r7 and r8 are clobbered.
         @ 1b = first critical insn, 2b = last critical insn.
-        @ If r2 >= 1b and r2 <= 2b then saved pc_usr is set to 1b.
+        @ If r4 >= 1b and r4 <= 2b then saved pc_usr is set to 1b.
         mov     r7, #0xffff0fff
         sub     r7, r7, #(0xffff0fff - (0xffff0fc0 + (1b - __kuser_cmpxchg)))
-        subs    r8, r2, r7
+        subs    r8, r4, r7
         rsbcss  r8, r8, #(2b - 1b)
         strcs   r7, [sp, #S_PC]
         mov     pc, lr