[PATCH 1/2] ARC: [Review] Preparing to fix incorrect syscall restarts due to signals
From: Vineet Gupta
Date: Fri Dec 28 2012 - 07:47:06 EST
To avoid multiple syscall restarts (multiple signals) or no restart at
all (sigreturn), we need just an extra bit of state "literally 1 bit" in
struct pt_regs. orig_r8 is the best place to do this, however given the
way it is encoded currently, we can't add anything simplistically.
Current orig_r8:
* syscalls -> 1 to NR_SYSCALLS
* Exceptions -> NR_SYSCALLS + 1
* Break-point-> NR_SYSCALLS + 2
In new scheme it is a bit-field
* lower short word contains the exact event type (and a new bit to represent
restart semantics : if syscall was already / can't be restarted)
* upper short word optionally containing the syscall num - needed by
likes of tracehooks etc
This change only changes the value orig_r8 is organised and nothing
should change behaviourily.
Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
---
arch/arc/include/asm/entry.h | 31 ++++++++++++++++++-------------
arch/arc/include/asm/ptrace.h | 17 ++++++++++++-----
arch/arc/kernel/entry.S | 10 +++++-----
3 files changed, 35 insertions(+), 23 deletions(-)
diff --git a/arch/arc/include/asm/entry.h b/arch/arc/include/asm/entry.h
index 4b8619e..414007a 100644
--- a/arch/arc/include/asm/entry.h
+++ b/arch/arc/include/asm/entry.h
@@ -415,18 +415,12 @@
*-------------------------------------------------------------*/
.macro SAVE_ALL_EXCEPTION marker
+ st \marker, [sp, 8]
+ st r0, [sp, 4] /* orig_r0, needed only for sys calls */
+
/* Restore r9 used to code the early prologue */
EXCPN_PROLOG_RESTORE_REG r9
- /* Save the complete regfile now */
-
- /* orig_r8 marker:
- * syscalls -> 1 to NR_SYSCALLS
- * Exceptions -> NR_SYSCALLS + 1
- * Break-point-> NR_SYSCALLS + 2
- */
- st \marker, [sp, 8]
- st r0, [sp, 4] /* orig_r0, needed only for sys calls */
SAVE_CALLER_SAVED
st.a r26, [sp, -4] /* gp */
st.a fp, [sp, -4]
@@ -456,14 +450,25 @@
* Save scratch regs for exceptions
*-------------------------------------------------------------*/
.macro SAVE_ALL_SYS
- SAVE_ALL_EXCEPTION (NR_syscalls + 1)
+ SAVE_ALL_EXCEPTION orig_r8_IS_EXCPN
.endm
/*--------------------------------------------------------------
* Save scratch regs for sys calls
*-------------------------------------------------------------*/
.macro SAVE_ALL_TRAP
- SAVE_ALL_EXCEPTION r8
+ /*
+ * Encode syscall number (r8) in upper short word of event type (r9)
+ * (r9 is already clobbered when we land here)
+ */
+#ifndef CONFIG_CPU_BIG_ENDIAN
+ lsl r9, r8, 16
+ or r9, r9, orig_r8_IS_SCALL
+#else
+ lsl r9, orig_r8_IS_SCALL, 16
+ or r9, r9, r8
+#endif
+ SAVE_ALL_EXCEPTION r9
.endm
/*--------------------------------------------------------------
@@ -518,7 +523,7 @@
#endif
/* now we are ready to save the remaining context :) */
- st -1, [sp, 8] /* orig_r8, -1 for interuppt level one */
+ st orig_r8_IS_IRQ1, [sp, 8] /* Event Type */
st 0, [sp, 4] /* orig_r0 , N/A for IRQ */
SAVE_CALLER_SAVED
st.a r26, [sp, -4] /* gp */
@@ -553,7 +558,7 @@
ld r9, [@int2_saved_reg]
/* now we are ready to save the remaining context :) */
- st -2, [sp, 8] /* orig_r8, -2 for interrupt level 2 */
+ st orig_r8_IS_IRQ2, [sp, 8] /* Event Type */
st 0, [sp, 4] /* orig_r0 , N/A for IRQ */
SAVE_CALLER_SAVED
st.a r26, [sp, -4] /* gp */
diff --git a/arch/arc/include/asm/ptrace.h b/arch/arc/include/asm/ptrace.h
index f38580c..7daa3a6 100644
--- a/arch/arc/include/asm/ptrace.h
+++ b/arch/arc/include/asm/ptrace.h
@@ -50,7 +50,8 @@ struct pt_regs {
long r0;
long sp; /* user/kernel sp depending on where we came from */
long orig_r0;
- long orig_r8; /*to distinguish bet excp, sys call, int1 or int2 */
+ /*to distinguish bet excp, syscall, irq */
+ unsigned long event_type:16, orig_r8:16;
};
/* Callee saved registers - need to be saved only when you are scheduled out */
@@ -89,9 +90,8 @@ struct user_regs_struct {
/* return 1 if PC in delay slot */
#define delay_mode(regs) ((regs->status32 & STATUS_DE_MASK) == STATUS_DE_MASK)
-/* return 1 if in syscall, 0 if Intr or Exception */
-#define in_syscall(regs) (((regs->orig_r8) >= 0 && \
- (regs->orig_r8 <= NR_syscalls)) ? 1 : 0)
+#define in_syscall(regs) (regs->orig_r8 & orig_r8_IS_SCALL)
+#define in_brkpt_trap(regs) (regs->orig_r8 & orig_r8_IS_BRKPT)
#define current_pt_regs() \
({ \
@@ -101,7 +101,6 @@ struct user_regs_struct {
(struct pt_regs *)(pg_start + THREAD_SIZE - 4) - 1; \
})
-#define in_brkpt_trap(regs) (((regs->orig_r8) == (NR_syscalls + 2)) ? 1 : 0)
#define user_stack_pointer(regs)\
({ unsigned int sp; \
@@ -112,6 +111,14 @@ struct user_regs_struct {
sp; \
})
+
#endif /* !__ASSEMBLY__ */
+#define orig_r8_IS_SCALL 0x0001
+#define orig_r8_IS_SCALL_RESTARTED 0x0002
+#define orig_r8_IS_BRKPT 0x0004
+#define orig_r8_IS_EXCPN 0x0004
+#define orig_r8_IS_IRQ1 0x0010
+#define orig_r8_IS_IRQ2 0x0020
+
#endif /* __ASM_PTRACE_H */
diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S
index 365a01b..f509306 100644
--- a/arch/arc/kernel/entry.S
+++ b/arch/arc/kernel/entry.S
@@ -500,8 +500,8 @@ tracesys_exit:
trap_with_param:
- ;make sure orig_r8 is a positive value
- st NR_syscalls + 2, [sp, PT_orig_r8]
+ ; stop_pc info by gdb needs this info
+ st orig_r8_IS_BRKPT, [sp, PT_orig_r8]
mov r0, r12
lr r1, [efa]
@@ -727,10 +727,10 @@ not_exception:
;----------------------------------------------------------------
ld r9, [sp, PT_orig_r8] ; get orig_r8 to make sure it is
- brne r9, -2, 149f ; infact a L2 ISR ret path
+ brne r9, orig_r8_IS_IRQ2, 149f ; infact a L2 ISR ret path
- ld r9, [sp, PT_status32] ; get statu32_l2 (saved in pt_regs)
- bbit0 r9, STATUS_A1_BIT, 149f ; L1 not active when L2 IRQ, so normal
+ ld r9, [sp, PT_status32] ; get statu32_l2 (saved in pt_regs)
+ bbit0 r9, STATUS_A1_BIT, 149f ; L1 not active when L2 IRQ, so normal
; A1 is set in status32_l2
; decrement thread_info->preempt_count (re-enable preemption)
--
1.7.4.1
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