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ARC: [Review] Preparing to fix incorrect syscall restarts due to signals

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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@synopsys.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
This commit is contained in:
Vineet Gupta
2013-02-11 20:01:24 +05:30
parent c3581039b6
commit 5c39c0ab5e
4 changed files with 40 additions and 19 deletions
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24
arch/arc/include/asm/ptrace.h
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@@ -50,7 +50,17 @@ 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 */
union {
#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
long orig_r8_word;
};
};
/* Callee saved registers - need to be saved only when you are scheduled out */
@@ -87,9 +97,8 @@ struct callee_regs {
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() \
({ \
@@ -101,6 +110,13 @@ struct callee_regs {
#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__ */
#ifndef __ASSEMBLY__