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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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2
arch/arc/kernel/asm-offsets.c
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@@ -46,7 +46,7 @@ int main(void)
BLANK();
DEFINE(PT_status32, offsetof(struct pt_regs, status32));
DEFINE(PT_orig_r8, offsetof(struct pt_regs, orig_r8));
DEFINE(PT_orig_r8, offsetof(struct pt_regs, orig_r8_word));
DEFINE(PT_sp, offsetof(struct pt_regs, sp));
DEFINE(PT_r0, offsetof(struct pt_regs, r0));
DEFINE(PT_r1, offsetof(struct pt_regs, r1));