powerpc, hw_breakpoint: Fix off-by-one in checking access address
The code would accept an access to an address one byte past the end
of the requested range as legitimate, due to having a "<=" rather than
a "<". This fixes that and cleans up the code a bit.
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c
index ed39805..241e097 100644
--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -197,7 +197,6 @@
*/
int __kprobes hw_breakpoint_handler(struct die_args *args)
{
- bool is_ptrace_bp = false;
int rc = NOTIFY_STOP;
struct perf_event *bp;
struct pt_regs *regs = args->regs;
@@ -208,6 +207,7 @@
/* Disable breakpoints during exception handling */
set_dabr(0);
+
/*
* The counter may be concurrently released but that can only
* occur from a call_rcu() path. We can then safely fetch
@@ -220,8 +220,6 @@
if (!bp)
goto out;
info = counter_arch_bp(bp);
- is_ptrace_bp = (bp->overflow_handler == ptrace_triggered) ?
- true : false;
/*
* Return early after invoking user-callback function without restoring
@@ -229,7 +227,7 @@
* one-shot mode. The ptrace-ed process will receive the SIGTRAP signal
* generated in do_dabr().
*/
- if (is_ptrace_bp) {
+ if (bp->overflow_handler == ptrace_triggered) {
perf_bp_event(bp, regs);
rc = NOTIFY_DONE;
goto out;
@@ -237,19 +235,12 @@
/*
* Verify if dar lies within the address range occupied by the symbol
- * being watched to filter extraneous exceptions.
+ * being watched to filter extraneous exceptions. If it doesn't,
+ * we still need to single-step the instruction, but we don't
+ * generate an event.
*/
- 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;
+ info->extraneous_interrupt = !((bp->attr.bp_addr <= dar) &&
+ (dar - bp->attr.bp_addr < bp->attr.bp_len));
/* Do not emulate user-space instructions, instead single-step them */
if (user_mode(regs)) {