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 patch only changes how orig_r8 is organised and nothing should
change behaviourily.
Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
arch/arc/include/asm/entry.h | 29 +++++++++++++++++------------
arch/arc/include/asm/ptrace.h | 20 ++++++++++++++++----
arch/arc/kernel/entry.S | 4 ++--
3 files changed, 35 insertions(+), 18 deletions(-)
diff --git a/arch/arc/include/asm/entry.h b/arch/arc/include/asm/entry.h
index 6b42bf5..9eada5b 100644
--- a/arch/arc/include/asm/entry.h
+++ b/arch/arc/include/asm/entry.h
@@ -343,18 +343,12 @@
*-------------------------------------------------------------*/
.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]
@@ -384,14 +378,25 @@
* 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
+ /*
+ * Setup pt_regs->orig_r8.
+ * Encode syscall number (r8) in upper short word of event type (r9)
+ * N.B. #1: This is already endian safe (see ptrace.h)
+ * #2: Only r9 can be used as scratch as it is already clobbered
+ * and it's contents are no longer needed by the latter part
+ * of exception prologue
+ */
+ lsl r9, r8, 16
+ or r9, r9, orig_r8_IS_SCALL
+
+ SAVE_ALL_EXCEPTION r9
.endm
/*--------------------------------------------------------------
@@ -442,7 +447,7 @@
ld r9, [@int1_saved_reg]
/* 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 */
diff --git a/arch/arc/include/asm/ptrace.h b/arch/arc/include/asm/ptrace.h
index 72754a2..1711d56 100644
--- a/arch/arc/include/asm/ptrace.h
+++ b/arch/arc/include/asm/ptrace.h
@@ -81,7 +81,13 @@ 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 */
+#ifdef CONFIG_CPU_BIG_ENDIAN
+ /* so that assembly code is same for LE/BE */
+ unsigned long orig_r8:16, event:16;
+#else
+ unsigned long event:16, orig_r8:16;
+#endif
};
/* Callee saved registers - need to be saved only when you are scheduled out */
@@ -126,9 +132,8 @@ struct user_regs_struct {
sp; \
})
-/* 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->event & orig_r8_IS_SCALL)
+#define in_brkpt_trap(regs) (regs->event & orig_r8_IS_BRKPT)
#define current_pt_regs() \
({ \
@@ -140,6 +145,13 @@ struct user_regs_struct {
#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 /* __KERNEL__ */
#endif /* __ASM_PTRACE_H */
diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S
index d625b77..ce8670d 100644
--- a/arch/arc/kernel/entry.S
+++ b/arch/arc/kernel/entry.S
@@ -350,8 +350,8 @@ ARC_EXIT EV_Extension
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]
--
1.7.4.1
--
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