Commit-ID: aa512a27e9e8ed32f31b15eec67ab1ceca33839b Gitweb: http://git.kernel.org/tip/aa512a27e9e8ed32f31b15eec67ab1ceca33839b Author: Steven Rostedt <srostedt@xxxxxxxxxx> AuthorDate: Wed, 13 May 2009 13:52:19 -0400 Committer: Steven Rostedt <rostedt@xxxxxxxxxxx> CommitDate: Wed, 13 May 2009 13:52:19 -0400 x86/function-graph: fix constraint for recording old return value After upgrading from gcc 4.2.2 to 4.4.0, the function graph tracer broke. Investigating, I found that in the asm that replaces the return value, gcc was using the same register for the old value as it was for the new value. mov (addr), old mov new, (addr) But if old and new are the same register, we clobber new with old! I first thought this was a bug in gcc 4.4.0 and reported it: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40132 Andrew Pinski responded (quickly), saying that it was correct gcc behavior and the code needed to denote old as an "early clobber". Instead of "=r"(old), we need "=&r"(old). [Impact: keep function graph tracer from breaking with gcc 4.4.0 ] Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx> --- arch/x86/kernel/ftrace.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 18dfa30..b79c553 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -442,7 +442,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr) _ASM_EXTABLE(1b, 4b) _ASM_EXTABLE(2b, 4b) - : [old] "=r" (old), [faulted] "=r" (faulted) + : [old] "=&r" (old), [faulted] "=r" (faulted) : [parent] "r" (parent), [return_hooker] "r" (return_hooker) : "memory" ); -- 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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