ptrace/x86: dont delay "disable" till second pass in ptrace_write_dr7()
ptrace_write_dr7() skips ptrace_modify_breakpoint(disabled => true) unless second_pass, this buys nothing but complicates the code and means that we always do the main loop twice even if "disabled" was never true. The comment says: Don't unregister the breakpoints right-away, unless all register_user_hw_breakpoint() requests have succeeded. Firstly, we do not do register_user_hw_breakpoint(), it was removed by commit24f1e32c60
("hw-breakpoints: Rewrite the hw-breakpoints layer on top of perf events"). We are going to restore register_user_hw_breakpoint() (see the next patch) but this doesn't matter: after commit44234adcdc
("hw-breakpoints: Modify breakpoints without unregistering them") perf_event_disable() can not hurt, hw_breakpoint_del() does not free the slot. Remove the "second_pass" check from the main loop and simplify the code. Since we have to check "bp != NULL" anyway, the patch also removes the same check in ptrace_modify_breakpoint() and moves the comment into ptrace_write_dr7(). With this patch the second pass is only needed to restore the saved old_dr7. This should never fail, so the patch adds WARN_ON() to catch the potential problems as Frederic suggested. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Jan Kratochvil <jan.kratochvil@redhat.com> Cc: Michael Neuling <mikey@neuling.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Paul Mundt <lethal@linux-sh.org> Cc: Will Deacon <will.deacon@arm.com> Cc: Prasad <prasad@linux.vnet.ibm.com> Cc: Russell King <linux@arm.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
e6a7d60771
commit
29a5551341
|
@ -609,14 +609,6 @@ ptrace_modify_breakpoint(struct perf_event *bp, int len, int type,
|
|||
int gen_len, gen_type;
|
||||
struct perf_event_attr attr;
|
||||
|
||||
/*
|
||||
* We should have at least an inactive breakpoint at this
|
||||
* slot. It means the user is writing dr7 without having
|
||||
* written the address register first
|
||||
*/
|
||||
if (!bp)
|
||||
return -EINVAL;
|
||||
|
||||
err = arch_bp_generic_fields(len, type, &gen_len, &gen_type);
|
||||
if (err)
|
||||
return err;
|
||||
|
@ -634,52 +626,47 @@ ptrace_modify_breakpoint(struct perf_event *bp, int len, int type,
|
|||
*/
|
||||
static int ptrace_write_dr7(struct task_struct *tsk, unsigned long data)
|
||||
{
|
||||
struct thread_struct *thread = &(tsk->thread);
|
||||
struct thread_struct *thread = &tsk->thread;
|
||||
unsigned long old_dr7;
|
||||
int i, orig_ret = 0, rc = 0;
|
||||
int second_pass = 0;
|
||||
bool second_pass = false;
|
||||
int i, rc, ret = 0;
|
||||
|
||||
data &= ~DR_CONTROL_RESERVED;
|
||||
old_dr7 = ptrace_get_dr7(thread->ptrace_bps);
|
||||
|
||||
restore:
|
||||
/*
|
||||
* Loop through all the hardware breakpoints, making the
|
||||
* appropriate changes to each.
|
||||
*/
|
||||
rc = 0;
|
||||
for (i = 0; i < HBP_NUM; i++) {
|
||||
unsigned len, type;
|
||||
bool disabled = !decode_dr7(data, i, &len, &type);
|
||||
struct perf_event *bp = thread->ptrace_bps[i];
|
||||
|
||||
if (disabled) {
|
||||
/*
|
||||
* Don't unregister the breakpoints right-away, unless
|
||||
* all register_user_hw_breakpoint() requests have
|
||||
* succeeded. This prevents any window of opportunity
|
||||
* for debug register grabbing by other users.
|
||||
*/
|
||||
if (!bp || !second_pass)
|
||||
if (!bp) {
|
||||
if (disabled)
|
||||
continue;
|
||||
/*
|
||||
* We should have at least an inactive breakpoint at
|
||||
* this slot. It means the user is writing dr7 without
|
||||
* having written the address register first.
|
||||
*/
|
||||
rc = -EINVAL;
|
||||
break;
|
||||
}
|
||||
|
||||
rc = ptrace_modify_breakpoint(bp, len, type, tsk, disabled);
|
||||
if (rc)
|
||||
break;
|
||||
}
|
||||
/*
|
||||
* Make a second pass to free the remaining unused breakpoints
|
||||
* or to restore the original breakpoints if an error occurred.
|
||||
*/
|
||||
if (!second_pass) {
|
||||
second_pass = 1;
|
||||
if (rc < 0) {
|
||||
orig_ret = rc;
|
||||
|
||||
/* Restore if the first pass failed, second_pass shouldn't fail. */
|
||||
if (rc && !WARN_ON(second_pass)) {
|
||||
ret = rc;
|
||||
data = old_dr7;
|
||||
}
|
||||
second_pass = true;
|
||||
goto restore;
|
||||
}
|
||||
|
||||
return orig_ret < 0 ? orig_ret : rc;
|
||||
return ret;
|
||||
}
|
||||
|
||||
/*
|
||||
|
|
Loading…
Reference in New Issue