[PATCH 5/6] x86-64: Omit frame pointers on vread_tsc

[Andy Lutomirski]

vread_tsc is short and hot, and it's userspace code so the usual
reasons to keep frame pointers around don't apply.

Signed-off-by: Andy Lutomirski <luto@xxxxxxx>
---

It might be nicer to move vread_tsc into a separate file and change
the options directly.

 arch/x86/kernel/tsc.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index a159fba..1aea4a6 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -764,6 +764,8 @@ static cycle_t read_tsc(struct clocksource *cs)
 }
 
 #ifdef CONFIG_X86_64
+#pragma GCC push_options
+#pragma GCC optimize ("omit-frame-pointer")
 static cycle_t __vsyscall_fn vread_tsc(void)
 {
 	cycle_t ret;
@@ -807,6 +809,7 @@ static cycle_t __vsyscall_fn vread_tsc(void)
 	asm volatile ("");
 	return last;
 }
+#pragma GCC pop_options
 #endif
 
 static void resume_tsc(struct clocksource *cs)
-- 
1.7.4

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