[PATCH 1/2] powerpc/hw_brk: Fix setting of length for exact mode breakpoints

[PATCH 1/2] powerpc/hw_brk: Fix setting of length for exact mode breakpoints

[Michael Neuling]

The smallest match region for both the DABR and DAWR is 8 bytes, so the
kernel needs to filter matches when users want to look at regions smaller than
this.

Currently we set the length of PPC_BREAKPOINT_MODE_EXACT breakpoints to 8.
This is wrong as in exact mode we should only match on 1 address, hence the
length should be 1.

This ensures that the kernel will filter out any exact mode hardware breakpoint
matches on any addresses other than the requested one.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Reported-by: Edjunior Barbosa Machado <emachado@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
---
 arch/powerpc/kernel/ptrace.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index 98c2fc1..64f7bd5 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -1449,7 +1449,9 @@ static long ppc_set_hwdebug(struct task_struct *child,
 	 */
 	if (bp_info->addr_mode == PPC_BREAKPOINT_MODE_RANGE_INCLUSIVE) {
 		len = bp_info->addr2 - bp_info->addr;
-	} else if (bp_info->addr_mode != PPC_BREAKPOINT_MODE_EXACT) {
+	} else if (bp_info->addr_mode == PPC_BREAKPOINT_MODE_EXACT)
+		len = 1;
+	else {
 		ptrace_put_breakpoints(child);
 		return -EINVAL;
 	}
-- 
1.7.10.4

[PATCH 2/2] powerpc/hw_brk: Fix clearing of extraneous IRQ

[Michael Neuling]

In 9422de3 "powerpc: Hardware breakpoints rewrite to handle non DABR breakpoint
registers" we changed the way we mark extraneous irqs with this:

-	info->extraneous_interrupt = !((bp->attr.bp_addr <= dar) &&
-			(dar - bp->attr.bp_addr < bp->attr.bp_len));
+	if (!((bp->attr.bp_addr <= dar) &&
+	      (dar - bp->attr.bp_addr < bp->attr.bp_len)))
+		info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;

Unfortunately this is bogus as it never clears extraneous IRQ if it's already
set.

This correctly clears extraneous IRQ before possibly setting it.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Reported-by: Edjunior Barbosa Machado <emachado@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
---
 arch/powerpc/kernel/hw_breakpoint.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c
index a949bdf..1150ae7 100644
--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -250,6 +250,7 @@ int __kprobes hw_breakpoint_handler(struct die_args *args)
 	 * we still need to single-step the instruction, but we don't
 	 * generate an event.
 	 */
+	info->type &= ~HW_BRK_TYPE_EXTRANEOUS_IRQ;
 	if (!((bp->attr.bp_addr <= dar) &&
 	      (dar - bp->attr.bp_addr < bp->attr.bp_len)))
 		info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
-- 
1.7.10.4

Re: [PATCH 2/2] powerpc/hw_brk: Fix clearing of extraneous IRQ

[Anshuman Khandual]

On 06/24/2013 11:17 AM, Michael Neuling wrote:
> In 9422de3 "powerpc: Hardware breakpoints rewrite to handle non DABR breakpoint
> registers" we changed the way we mark extraneous irqs with this:
> 
> -	info->extraneous_interrupt = !((bp->attr.bp_addr <= dar) &&
> -			(dar - bp->attr.bp_addr < bp->attr.bp_len));
> +	if (!((bp->attr.bp_addr <= dar) &&
> +	      (dar - bp->attr.bp_addr < bp->attr.bp_len)))
> +		info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
> 
> Unfortunately this is bogus as it never clears extraneous IRQ if it's already
> set.
> 
> This correctly clears extraneous IRQ before possibly setting it.
> 
> Signed-off-by: Michael Neuling <mikey@neuling.org>
Reviewed-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>

Re: [PATCH 1/2] powerpc/hw_brk: Fix setting of length for exact mode breakpoints

[Anshuman Khandual]

On 06/24/2013 11:17 AM, Michael Neuling wrote:
> The smallest match region for both the DABR and DAWR is 8 bytes, so the
> kernel needs to filter matches when users want to look at regions smaller than
> this.
> 
> Currently we set the length of PPC_BREAKPOINT_MODE_EXACT breakpoints to 8.
> This is wrong as in exact mode we should only match on 1 address, hence the
> length should be 1.
> 
> This ensures that the kernel will filter out any exact mode hardware breakpoint
> matches on any addresses other than the requested one.
> 
> Signed-off-by: Michael Neuling <mikey@neuling.org>

Reviewed-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>