Commit-ID: eb1e79611cc9bfe21978230e3521e77ea2d7874a Gitweb: http://git.kernel.org/tip/eb1e79611cc9bfe21978230e3521e77ea2d7874a Author: Frederic Weisbecker <fweisbec@xxxxxxxxx> AuthorDate: Tue, 23 Mar 2010 00:08:59 +0100 Committer: Frederic Weisbecker <fweisbec@xxxxxxxxx> CommitDate: Thu, 1 Apr 2010 08:26:30 +0200 perf: Correctly align perf event tracing buffer The trace event buffer used by perf to record raw sample events is typed as an array of char and may then not be aligned to 8 by alloc_percpu(). But we need it to be aligned to 8 in sparc64 because we cast this buffer into a random structure type built by the TRACE_EVENT() macro to store the traces. So if a random 64 bits field is accessed inside, it may be not under an expected good alignment. Use an array of long instead to force the appropriate alignment, and perform a compile time check to ensure the size in byte of the buffer is a multiple of sizeof(long) so that its actual size doesn't get shrinked under us. This fixes unaligned accesses reported while using perf lock in sparc 64. Suggested-by: David Miller <davem@xxxxxxxxxxxxx> Suggested-by: Tejun Heo <htejun@xxxxxxxxx> Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxx> Cc: David Miller <davem@xxxxxxxxxxxxx> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> --- kernel/trace/trace_event_perf.c | 11 +++++++++-- 1 files changed, 9 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c index 81f691e..0565bb4 100644 --- a/kernel/trace/trace_event_perf.c +++ b/kernel/trace/trace_event_perf.c @@ -17,7 +17,12 @@ EXPORT_SYMBOL_GPL(perf_arch_fetch_caller_regs); static char *perf_trace_buf; static char *perf_trace_buf_nmi; -typedef typeof(char [PERF_MAX_TRACE_SIZE]) perf_trace_t ; +/* + * Force it to be aligned to unsigned long to avoid misaligned accesses + * suprises + */ +typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)]) + perf_trace_t; /* Count the events in use (per event id, not per instance) */ static int total_ref_count; @@ -130,6 +135,8 @@ __kprobes void *perf_trace_buf_prepare(int size, unsigned short type, char *trace_buf, *raw_data; int pc, cpu; + BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long)); + pc = preempt_count(); /* Protect the per cpu buffer, begin the rcu read side */ @@ -152,7 +159,7 @@ __kprobes void *perf_trace_buf_prepare(int size, unsigned short type, raw_data = per_cpu_ptr(trace_buf, cpu); /* zero the dead bytes from align to not leak stack to user */ - *(u64 *)(&raw_data[size - sizeof(u64)]) = 0ULL; + memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64)); entry = (struct trace_entry *)raw_data; tracing_generic_entry_update(entry, *irq_flags, pc); -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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