Messages in this thread Patch in this message | | | From | Jiri Olsa <> | Subject | [PATCH 2/2] perf/hw_breakpoint: Modify breakpoint even if the new attr has disabled set | Date | Mon, 6 Aug 2018 12:12:41 +0200 |
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We need to change the breakpoint even if the attr with new fields has disabled set to true.
Current code prevents following user code to change the breakpoint address:
ptrace(PTRACE_POKEUSER, child, offsetof(struct user, u_debugreg[0]), addr_1) ptrace(PTRACE_POKEUSER, child, offsetof(struct user, u_debugreg[0]), addr_2) ptrace(PTRACE_POKEUSER, child, offsetof(struct user, u_debugreg[7]), dr7)
The first PTRACE_POKEUSER creates the breakpoint with attr.disabled set to true:
ptrace_set_breakpoint_addr(nr = 0) struct perf_event *bp = t->ptrace_bps[nr];
ptrace_register_breakpoint(..., disabled = true) ptrace_fill_bp_fields(..., disabled) register_user_hw_breakpoint
So the second PTRACE_POKEUSER will be omitted:
ptrace_set_breakpoint_addr(nr = 0) struct perf_event *bp = t->ptrace_bps[nr]; struct perf_event_attr attr = bp->attr;
modify_user_hw_breakpoint(bp, &attr) if (!attr->disabled) modify_user_hw_breakpoint_check
Cc: Milind Chabbi <chabbi.milind@gmail.com> Link: http://lkml.kernel.org/n/tip-yjhgplc28gk5gfzt7ceooe6z@git.kernel.org Signed-off-by: Jiri Olsa <jolsa@kernel.org> --- kernel/events/hw_breakpoint.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c index b3814fce5ecb..fb229d9c7f3c 100644 --- a/kernel/events/hw_breakpoint.c +++ b/kernel/events/hw_breakpoint.c @@ -509,6 +509,8 @@ modify_user_hw_breakpoint_check(struct perf_event *bp, struct perf_event_attr *a */ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr) { + int err; + /* * modify_user_hw_breakpoint can be invoked with IRQs disabled and hence it * will not be possible to raise IPIs that invoke __perf_event_disable. @@ -520,11 +522,11 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att else perf_event_disable(bp); - if (!attr->disabled) { - int err = modify_user_hw_breakpoint_check(bp, attr, false); + err = modify_user_hw_breakpoint_check(bp, attr, false); + if (err) + return err; - if (err) - return err; + if (!attr->disabled) { perf_event_enable(bp); bp->attr.disabled = 0; } -- 2.17.1
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