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Date: Thu, 24 Jan 2013 16:20:23 +0530
From: Vineet Gupta <Vineet.Gupta1@...opsys.com>
To: <linux-arch@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <arnd@...db.de>, Vineet Gupta <Vineet.Gupta1@...opsys.com>,
Al Viro <viro@...IV.linux.org.uk>
Subject: [PATCH v3 21/71] ARC: [Review] Preparing to fix incorrect syscall restarts due to signals
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@...opsys.com>
Cc: Al Viro <viro@...IV.linux.org.uk>
---
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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