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| author | Matt Evans <matt@ozlabs.org> | 2018-03-26 17:55:21 +0100 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2018-04-01 22:15:33 +1000 |
| commit | 0e524e761fc2157f1037e0f5d616cd39e468d89c (patch) | |
| tree | eb7c275ed3c776f36de13f59fb65c2d4023f83af /arch/powerpc/kernel/traps.c | |
| parent | 4b7e5532d2113d002aa54bfe581f35b3f1f72306 (diff) | |
| download | linux-0e524e761fc2157f1037e0f5d616cd39e468d89c.tar.gz | |
powerpc: Clear branch trap (MSR.BE) before delivering SIGTRAP
When using SIG_DBG_BRANCH_TRACING, MSR.BE is left enabled in the
user context when single_step_exception() prepares the SIGTRAP
delivery. The resulting branch-trap-within-the-SIGTRAP-handler
isn't healthy.
Commit 2538c2d08f46141550a1e68819efa8fe31c6e3dc broke this, by
replacing an MSR mask operation of ~(MSR_SE | MSR_BE) with a call
to clear_single_step() which only clears MSR_SE.
This patch adds a new helper, clear_br_trace(), which clears the
debug trap before invoking the signal handler. This helper is a
NOP for BookE as SIG_DBG_BRANCH_TRACING isn't supported on BookE.
Signed-off-by: Matt Evans <matt@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/kernel/traps.c')
| -rw-r--r-- | arch/powerpc/kernel/traps.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c index 2c1a1d24f0abb4..a2ef0c0e6c315b 100644 --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c @@ -471,7 +471,7 @@ static inline int check_io_access(struct pt_regs *regs) /* single-step stuff */ #define single_stepping(regs) (current->thread.debug.dbcr0 & DBCR0_IC) #define clear_single_step(regs) (current->thread.debug.dbcr0 &= ~DBCR0_IC) - +#define clear_br_trace(regs) do {} while(0) #else /* On non-4xx, the reason for the machine check or program exception is in the MSR. */ @@ -484,6 +484,7 @@ static inline int check_io_access(struct pt_regs *regs) #define single_stepping(regs) ((regs)->msr & MSR_SE) #define clear_single_step(regs) ((regs)->msr &= ~MSR_SE) +#define clear_br_trace(regs) ((regs)->msr &= ~MSR_BE) #endif #if defined(CONFIG_E500) @@ -999,6 +1000,7 @@ void single_step_exception(struct pt_regs *regs) enum ctx_state prev_state = exception_enter(); clear_single_step(regs); + clear_br_trace(regs); if (kprobe_post_handler(regs)) return; |