From bb7253403f7a4670a128e4c080fd8ea1bd4d5029 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 11 Feb 2009 12:45:49 -0800 Subject: [PATCH] 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 Acked-by: Benjamin Herrenschmidt Signed-off-by: Steven Rostedt Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/kernel/entry_64.S | 27 ++++++++++++++++++++++++++- arch/powerpc/kernel/ftrace.c | 13 +++++++++++-- 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 @@ -970,6 +970,28 @@ _GLOBAL(ftrace_graph_caller) blr _GLOBAL(return_to_handler) + /* need to save return values */ + std r4, -24(r1) + std r3, -16(r1) + std r31, -8(r1) + mr r31, r1 + stdu r1, -112(r1) + + bl .ftrace_return_to_handler + nop + + /* return value has real return address */ + mtlr r3 + + ld r1, 0(r1) + ld r4, -24(r1) + ld r3, -16(r1) + ld r31, -8(r1) + + /* Jump back to real return address */ + blr + +_GLOBAL(mod_return_to_handler) /* need to save return values */ std r4, -32(r1) std r3, -24(r1) @@ -979,7 +1001,10 @@ _GLOBAL(return_to_handler) mr r31, r1 stdu r1, -112(r1) - /* update the TOC */ + /* + * We are in a module using the module's TOC. + * Switch to our TOC to run inside the core kernel. + */ LOAD_REG_IMMEDIATE(r4,ftrace_return_to_handler) ld r2, 8(r4) 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) } #endif /* CONFIG_DYNAMIC_FTRACE */ +#ifdef CONFIG_PPC64 +extern void mod_return_to_handler(void); +#endif + /* * Hook the return address and push it in the stack of return addrs * in current thread info. @@ -577,12 +581,17 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr) unsigned long long calltime; int faulted; struct ftrace_graph_ent trace; - unsigned long return_hooker = (unsigned long) - &return_to_handler; + unsigned long return_hooker = (unsigned long)&return_to_handler; if (unlikely(atomic_read(¤t->tracing_graph_pause))) return; +#if CONFIG_PPC64 + /* non core kernel code needs to save and restore the TOC */ + if (REGION_ID(self_addr) != KERNEL_REGION_ID) + return_hooker = (unsigned long)&mod_return_to_handler; +#endif + return_hooker = GET_ADDR(return_hooker); /* -- GitLab