diff options
| author | K.Prasad <prasad@linux.vnet.ibm.com> | 2010-06-15 11:36:12 +0530 |
|---|---|---|
| committer | Paul Mackerras <paulus@samba.org> | 2010-06-22 19:40:51 +1000 |
| commit | e3e94084adb5610987283367574ebc771e8206e1 (patch) | |
| tree | 2787caa5a5f657a218d199b7dff8c7dcd326eb7f /arch/powerpc/kernel/hw_breakpoint.c | |
| parent | 06532a6743d83fac4b79389fc8c86c88cb4e3302 (diff) | |
powerpc, hw_breakpoint: Discard extraneous interrupt due to accesses outside symbol length
Many a times, the requested breakpoint length can be less than the
fixed breakpoint length i.e. 8 bytes supported by PowerPC 64-bit
server (Book III S) processors. This could lead to extraneous
interrupts resulting in false breakpoint notifications. This
detects and discards such interrupts for non-ptrace requests.
We don't change ptrace behaviour to avoid breaking compatability.
[Suggestion from Paul Mackerras <paulus@samba.org> to add a new flag in
'struct arch_hw_breakpoint' to identify extraneous interrupts]
Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch/powerpc/kernel/hw_breakpoint.c')
| -rw-r--r-- | arch/powerpc/kernel/hw_breakpoint.c | 23 |
1 files changed, 21 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c index 7bd01a56d19..ed39805a3b8 100644 --- a/arch/powerpc/kernel/hw_breakpoint.c +++ b/arch/powerpc/kernel/hw_breakpoint.c @@ -204,6 +204,7 @@ int __kprobes hw_breakpoint_handler(struct die_args *args) int stepped = 1; struct arch_hw_breakpoint *info; unsigned int instr; + unsigned long dar = regs->dar; /* Disable breakpoints during exception handling */ set_dabr(0); @@ -234,6 +235,22 @@ int __kprobes hw_breakpoint_handler(struct die_args *args) goto out; } + /* + * Verify if dar lies within the address range occupied by the symbol + * being watched to filter extraneous exceptions. + */ + if (!((bp->attr.bp_addr <= dar) && + (dar <= (bp->attr.bp_addr + bp->attr.bp_len)))) { + /* + * This exception is triggered not because of a memory access + * on the monitored variable but in the double-word address + * range in which it is contained. We will consume this + * exception, considering it as 'noise'. + */ + info->extraneous_interrupt = true; + } else + info->extraneous_interrupt = false; + /* Do not emulate user-space instructions, instead single-step them */ if (user_mode(regs)) { bp->ctx->task->thread.last_hit_ubp = bp; @@ -261,7 +278,8 @@ int __kprobes hw_breakpoint_handler(struct die_args *args) * As a policy, the callback is invoked in a 'trigger-after-execute' * fashion */ - perf_bp_event(bp, regs); + if (!info->extraneous_interrupt) + perf_bp_event(bp, regs); set_dabr(info->address | info->type | DABR_TRANSLATION); out: @@ -292,7 +310,8 @@ int __kprobes single_step_dabr_instruction(struct die_args *args) * We shall invoke the user-defined callback function in the single * stepping handler to confirm to 'trigger-after-execute' semantics */ - perf_bp_event(bp, regs); + if (!bp_info->extraneous_interrupt) + perf_bp_event(bp, regs); /* * Do not disable MSR_SE if the process was already in |