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ARC: Signal handling

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Includes following fixes courtesy review by Al-Viro

* Tracer poke to Callee-regs were lost

  Before going off into do_signal( ) we save the user-mode callee regs
  (as they are not saved by default as part of pt_regs). This is to make
  sure that that a Tracer (if tracing related signal) is able to do likes
  of PEEKUSR(callee-reg).

  However in return path we were simply discarding the user-mode callee
  regs, which would break a POKEUSR(callee-reg) from a tracer.

* Issue related to multiple syscall restarts are addressed in next patch

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Acked-by: Jonas Bonn <jonas@southpole.se>
This commit is contained in:
Vineet Gupta
2013-01-18 15:12:19 +05:30
parent d8005e6b95
commit c3581039b6
6 changed files with 449 additions and 3 deletions
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35
arch/arc/include/asm/entry.h
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@@ -165,6 +165,41 @@
.endm
/*--------------------------------------------------------------
* RESTORE_CALLEE_SAVED_USER:
* This is called after do_signal where tracer might have changed callee regs
* thus we need to restore the reg file.
* Special case handling is required for r25 in case it is used by kernel
* for caching task ptr. Ptrace would have modified on-kernel-stack value of
* r25, which needs to be shoved back into task->thread.user_r25 where from
* Low level exception/ISR return code will retrieve to populate with rest of
* callee reg-file.
*-------------------------------------------------------------*/
.macro RESTORE_CALLEE_SAVED_USER
add sp, sp, 4 /* skip "callee_regs->stack_place_holder" */
#ifdef CONFIG_ARC_CURR_IN_REG
ld.ab r12, [sp, 4]
st r12, [r25, TASK_THREAD + THREAD_USER_R25]
#else
ld.ab r25, [sp, 4]
#endif
ld.ab r24, [sp, 4]
ld.ab r23, [sp, 4]
ld.ab r22, [sp, 4]
ld.ab r21, [sp, 4]
ld.ab r20, [sp, 4]
ld.ab r19, [sp, 4]
ld.ab r18, [sp, 4]
ld.ab r17, [sp, 4]
ld.ab r16, [sp, 4]
ld.ab r15, [sp, 4]
ld.ab r14, [sp, 4]
ld.ab r13, [sp, 4]
.endm
/*--------------------------------------------------------------
* Super FAST Restore callee saved regs by simply re-adjusting SP
*-------------------------------------------------------------*/