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Commit c3581039 authored by Vineet Gupta's avatar Vineet Gupta
Browse files

ARC: Signal handling 



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: default avatarVineet Gupta <vgupta@synopsys.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Acked-by: default avatarJonas Bonn <jonas@southpole.se>
parent d8005e6b

arch/arc/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ config ARC 
	select GENERIC_KERNEL_EXECVE

	select GENERIC_KERNEL_THREAD

	select GENERIC_PENDING_IRQ if SMP

	select GENERIC_SIGALTSTACK

	select GENERIC_SMP_IDLE_THREAD

	select HAVE_GENERIC_HARDIRQS

	select MODULES_USE_ELF_RELA

arch/arc/include/asm/entry.h

+35 −0
Original line number Diff line number Diff line
@@ -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

 *-------------------------------------------------------------*/

arch/arc/include/asm/sigcontext.h

0 → 100644
+22 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */



#ifndef _ASM_ARC_SIGCONTEXT_H

#define _ASM_ARC_SIGCONTEXT_H



#include <asm/ptrace.h>



/*

 * Signal context structure - contains all info to do with the state

 * before the signal handler was invoked.

 */

struct sigcontext {

	struct user_regs_struct regs;

};



#endif /* _ASM_ARC_SIGCONTEXT_H */

arch/arc/include/asm/signal.h

0 → 100644
+27 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 *

 * Amit Bhor, Sameer Dhavale: Codito Technologies 2004

 */



#ifndef _ASM_ARC_SIGNAL_H

#define _ASM_ARC_SIGNAL_H



/*

 * This is much needed for ARC sigreturn optimization.

 * This allows uClibc to piggback the addr of a sigreturn stub in sigaction,

 * which allows sigreturn based re-entry into kernel after handling signal.

 * W/o this kernel needs to "synthesize" the sigreturn trampoline on user

 * mode stack which in turn forces the following:

 * -TLB Flush (after making the stack page executable)

 * -Cache line Flush (to make I/D Cache lines coherent)

 */

#define SA_RESTORER	0x04000000



#include <asm-generic/signal.h>



#endif /* _ASM_ARC_SIGNAL_H */

arch/arc/kernel/entry.S

+8 −3
Original line number Diff line number Diff line
@@ -470,7 +470,11 @@ resume_user_mode_begin: 


	bbit0  r9, TIF_SIGPENDING, .Lchk_notify_resume



	; save CALLEE Regs.

	; Normal Trap/IRQ entry only saves Scratch (caller-saved) regs

	; in pt_reg since the "C" ABI (kernel code) will automatically

	; save/restore callee-saved regs.

	;

	; However, here we need to explicitly save callee regs because

	; (i)  If this signal causes coredump - full regfile needed

	; (ii) If signal is SIGTRAP/SIGSTOP, task is being traced thus

	;      tracer might call PEEKUSR(CALLEE reg)
@@ -484,8 +488,9 @@ resume_user_mode_begin: 


	bl  @do_signal



	; unwind SP for cheap discard of Callee saved Regs

	DISCARD_CALLEE_SAVED_USER

	; Ideally we want to discard the Callee reg above, however if this was

	; a tracing signal, tracer could have done a POKEUSR(CALLEE reg)

	RESTORE_CALLEE_SAVED_USER



	b      resume_user_mode_begin	; loop back to start of U mode ret