perf, trace: Fix !x86 build bug

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From: Linux Kernel Mailing List
Date: Thursday, May 27, 2010 - 4:00 pm

Gitweb:     http://git.kernel.org/linus/87f44bbc246c5244c76a701f8eefba7788bce64a
Commit:     87f44bbc246c5244c76a701f8eefba7788bce64a
Parent:     d67f088e084755bdceb4f15bc6e05e309db1eea7
Author:     Peter Zijlstra <peterz@infradead.org>
AuthorDate: Tue May 25 11:02:55 2010 +0200
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Tue May 25 11:28:49 2010 +0200

    perf, trace: Fix !x86 build bug
    
    Patch b7e2ecef92 (perf, trace: Optimize tracepoints by removing
    IRQ-disable from perf/tracepoint interaction) made the
    unfortunate mistake of assuming the world is x86 only, correct
    this.
    
    The problem was that perf_fetch_caller_regs() did
    local_save_flags() into regs->flags, and I re-used that to
    remove another local_save_flags(), forgetting !x86 doesn't have
    regs->flags.
    
    Do the reverse, remove the local_save_flags() from
    perf_fetch_caller_regs() and let the ftrace site do the
    local_save_flags() instead.
    
    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Acked-by: Paul Mackerras <paulus@samba.org>
    Cc: acme@redhat.com
    Cc: efault@gmx.de
    Cc: fweisbec@gmail.com
    Cc: rostedt@goodmis.org
    LKML-Reference: <1274778175.5882.623.camel@twins>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/kernel/cpu/perf_event.c |    6 +++++-
 kernel/trace/trace_event_perf.c  |    4 +++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index fd4db0d..c775860 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1717,7 +1717,11 @@ void perf_arch_fetch_caller_regs(struct pt_regs *regs, unsigned long ip, int ski
 	 */
 	regs->bp = rewind_frame_pointer(skip + 1);
 	regs->cs = __KERNEL_CS;
-	local_save_flags(regs->flags);
+	/*
+	 * We abuse bit 3 to pass exact information, see perf_misc_flags
+	 * and the comment with PERF_EFLAGS_EXACT.
+	 */
+	regs->flags = 0;
 }
 
 unsigned long perf_instruction_pointer(struct pt_regs *regs)
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index 26b8607..cb6f365 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -157,6 +157,7 @@ __kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
 				       struct pt_regs *regs, int *rctxp)
 {
 	struct trace_entry *entry;
+	unsigned long flags;
 	char *raw_data;
 	int pc;
 
@@ -174,7 +175,8 @@ __kprobes void *perf_trace_buf_prepare(int size, unsigned short type,
 	memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));
 
 	entry = (struct trace_entry *)raw_data;
-	tracing_generic_entry_update(entry, regs->flags, pc);
+	local_save_flags(flags);
+	tracing_generic_entry_update(entry, flags, pc);
 	entry->type = type;
 
 	return raw_data;
--
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perf, trace: Fix !x86 build bug, Linux Kernel Mailing ..., (Thu May 27, 4:00 pm)