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parisc: improve ptrace support for gdb single-step

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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: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>
This commit is contained in:
John David Anglin 2012-12-28 23:18:01 +00:00 committed by Helge Deller
parent cac1f12b9f
commit 34360f080c
2 changed files with 15 additions and 7 deletions
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20
arch/parisc/kernel/entry.S
View file

@ -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)
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)
copy %r25,%r16
b intr_restore
nop
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
copy %r25,%r16
.import schedule,code
syscall_do_resched:

2
arch/parisc/kernel/ptrace.c
View file

@ -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..