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powerpc, hw_breakpoint: Fix off-by-one in checking access address

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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>
This commit is contained in:
Paul Mackerras 2010-06-23 15:42:43 +10:00
parent e3e94084ad
commit 574cb24899
1 changed files with 7 additions and 16 deletions
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23
arch/powerpc/kernel/hw_breakpoint.c
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@ -197,7 +197,6 @@ void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs)
*/
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 @@ int __kprobes hw_breakpoint_handler(struct die_args *args)
/* 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 @@ int __kprobes hw_breakpoint_handler(struct die_args *args)
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 @@ int __kprobes hw_breakpoint_handler(struct die_args *args)
* 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 @@ int __kprobes hw_breakpoint_handler(struct die_args *args)
/*
* 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)) {