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authorSteven Rostedt <srostedt@redhat.com>2009-02-11 15:45:49 -0500
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2009-02-22 18:48:54 -0500
commitbb7253403f7a4670a128e4c080fd8ea1bd4d5029 (patch)
treef2ee8c966035a67be77fad922ada4c4d52a53be9
parent465428884765b43d642a967915e16c6c7cacbe8e (diff)
powerpc64, ftrace: save toc only on modules for function graph
The TOCS used by modules are different than the one used by the core kernel code. The function graph tracer must save and restore the TOC whenever it traces a module call. But this is an added overhead to burden the majority of core kernel code being traced. Benjamin Herrenschmidt suggested in testing the entry of the call to tell if it is a core kernel function or a module. He recommended using the REGION_ID() macro to perform this test. This patch implements Benjamin's idea, and uses a different return_to_handler routine dependent on if the entry is a core kernel function or not. The module version saves the TOC, where as the core kernel version does not. Geoff Lavand tested on PS3. Tested-by: Geoff Levand <geoffrey.levand@am.sony.com> Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
-rw-r--r--arch/powerpc/kernel/entry_64.S27
-rw-r--r--arch/powerpc/kernel/ftrace.c13
2 files changed, 37 insertions, 3 deletions
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 9f61fd61f277..abfc32330479 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -971,6 +971,28 @@ _GLOBAL(ftrace_graph_caller)
971 971
972_GLOBAL(return_to_handler) 972_GLOBAL(return_to_handler)
973 /* need to save return values */ 973 /* need to save return values */
974 std r4, -24(r1)
975 std r3, -16(r1)
976 std r31, -8(r1)
977 mr r31, r1
978 stdu r1, -112(r1)
979
980 bl .ftrace_return_to_handler
981 nop
982
983 /* return value has real return address */
984 mtlr r3
985
986 ld r1, 0(r1)
987 ld r4, -24(r1)
988 ld r3, -16(r1)
989 ld r31, -8(r1)
990
991 /* Jump back to real return address */
992 blr
993
994_GLOBAL(mod_return_to_handler)
995 /* need to save return values */
974 std r4, -32(r1) 996 std r4, -32(r1)
975 std r3, -24(r1) 997 std r3, -24(r1)
976 /* save TOC */ 998 /* save TOC */
@@ -979,7 +1001,10 @@ _GLOBAL(return_to_handler)
979 mr r31, r1 1001 mr r31, r1
980 stdu r1, -112(r1) 1002 stdu r1, -112(r1)
981 1003
982 /* update the TOC */ 1004 /*
1005 * We are in a module using the module's TOC.
1006 * Switch to our TOC to run inside the core kernel.
1007 */
983 LOAD_REG_IMMEDIATE(r4,ftrace_return_to_handler) 1008 LOAD_REG_IMMEDIATE(r4,ftrace_return_to_handler)
984 ld r2, 8(r4) 1009 ld r2, 8(r4)
985 1010
diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index 7538b944fa52..5c6dfa97e838 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -567,6 +567,10 @@ int ftrace_disable_ftrace_graph_caller(void)
567} 567}
568#endif /* CONFIG_DYNAMIC_FTRACE */ 568#endif /* CONFIG_DYNAMIC_FTRACE */
569 569
570#ifdef CONFIG_PPC64
571extern void mod_return_to_handler(void);
572#endif
573
570/* 574/*
571 * Hook the return address and push it in the stack of return addrs 575 * Hook the return address and push it in the stack of return addrs
572 * in current thread info. 576 * in current thread info.
@@ -577,12 +581,17 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
577 unsigned long long calltime; 581 unsigned long long calltime;
578 int faulted; 582 int faulted;
579 struct ftrace_graph_ent trace; 583 struct ftrace_graph_ent trace;
580 unsigned long return_hooker = (unsigned long) 584 unsigned long return_hooker = (unsigned long)&return_to_handler;
581 &return_to_handler;
582 585
583 if (unlikely(atomic_read(&current->tracing_graph_pause))) 586 if (unlikely(atomic_read(&current->tracing_graph_pause)))
584 return; 587 return;
585 588
589#if CONFIG_PPC64
590 /* non core kernel code needs to save and restore the TOC */
591 if (REGION_ID(self_addr) != KERNEL_REGION_ID)
592 return_hooker = (unsigned long)&mod_return_to_handler;
593#endif
594
586 return_hooker = GET_ADDR(return_hooker); 595 return_hooker = GET_ADDR(return_hooker);
587 596
588 /* 597 /*