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Commit 34360f08 authored by John David Anglin's avatar John David Anglin Committed by Helge Deller
Browse files

parisc: improve ptrace support for gdb single-step 



Various GCC tests use gdb to simulate a multithreaded application. Many of
these tests have been failing on parisc linux.

GCC does this by using gdb to single-step the application, then gdb is used to
call other test specific code. Where this fails is when the application is
stepped into the delay slot of a taken branch. This sets the PSW B bit. When
the test specific code is executed, this usually clears the PSW B bit.
Currently, gdb is not allowed to set the B bit. So, the code falls through what
should be a taken branch.

The attached patch adds the PSW B bit to the set of bits that gdb is allowed to
set. In order to set the B bit, the trace system call must return using an
interrupt restore. The patch also modifies this code to use the saved IAOQ
values when they are saved by a ptrace syscall or interruption.

Signed-off-by: default avatarJohn David Anglin <dave.anglin@bell.net>
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
parent cac1f12b

arch/parisc/kernel/entry.S

+13 −5
Original line number Diff line number Diff line
@@ -1865,7 +1865,7 @@ syscall_restore: 


	/* Are we being ptraced? */

	ldw	TASK_FLAGS(%r1),%r19

	ldi	(_TIF_SINGLESTEP|_TIF_BLOCKSTEP),%r2

	ldi	_TIF_SYSCALL_TRACE_MASK,%r2

	and,COND(=)	%r19,%r2,%r0

	b,n	syscall_restore_rfi
@@ -1978,15 +1978,23 @@ syscall_restore_rfi: 
	/* sr2 should be set to zero for userspace syscalls */

	STREG	%r0,TASK_PT_SR2(%r1)



pt_regs_ok:

	LDREG	TASK_PT_GR31(%r1),%r2

	depi	3,31,2,%r2		   /* ensure return to user mode. */

	STREG   %r2,TASK_PT_IAOQ0(%r1)

	ldo	4(%r2),%r2

	STREG	%r2,TASK_PT_IAOQ1(%r1)

	b	intr_restore

	copy	%r25,%r16



pt_regs_ok:

	LDREG	TASK_PT_IAOQ0(%r1),%r2

	depi	3,31,2,%r2		   /* ensure return to user mode. */

	STREG	%r2,TASK_PT_IAOQ0(%r1)

	LDREG	TASK_PT_IAOQ1(%r1),%r2

	depi	3,31,2,%r2

	STREG	%r2,TASK_PT_IAOQ1(%r1)

	b	intr_restore

	nop

	copy	%r25,%r16



	.import schedule,code

syscall_do_resched:

arch/parisc/kernel/ptrace.c

+1 −1
Original line number Diff line number Diff line
@@ -26,7 +26,7 @@ 
#include <asm/asm-offsets.h>



/* PSW bits we allow the debugger to modify */

#define USER_PSW_BITS	(PSW_N | PSW_V | PSW_CB)

#define USER_PSW_BITS	(PSW_N | PSW_B | PSW_V | PSW_CB)



/*

 * Called by kernel/ptrace.c when detaching..