From 153086644fd1fb07fb3af84d9f11542a19b1e8b6 Mon Sep 17 00:00:00 2001 From: Torsten Duwe Date: Thu, 3 Mar 2016 15:26:59 +1100 Subject: powerpc/ftrace: Add support for -mprofile-kernel ftrace ABI The gcc switch -mprofile-kernel defines a new ABI for calling _mcount() very early in the function with minimal overhead. Although mprofile-kernel has been available since GCC 3.4, there were bugs which were only fixed recently. Currently it is known to work in GCC 4.9, 5 and 6. Additionally there are two possible code sequences generated by the flag, the first uses mflr/std/bl and the second is optimised to omit the std. Currently only gcc 6 has the optimised sequence. This patch supports both sequences. Initial work started by Vojtech Pavlik, used with permission. Key changes: - rework _mcount() to work for both the old and new ABIs. - implement new versions of ftrace_caller() and ftrace_graph_caller() which deal with the new ABI. - updates to __ftrace_make_nop() to recognise the new mcount calling sequence. - updates to __ftrace_make_call() to recognise the nop'ed sequence. - implement ftrace_modify_call(). - updates to the module loader to surpress the toc save in the module stub when calling mcount with the new ABI. Reviewed-by: Balbir Singh Signed-off-by: Torsten Duwe Signed-off-by: Michael Ellerman --- arch/powerpc/include/asm/code-patching.h | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'arch/powerpc/include/asm/code-patching.h') diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h index 840a5509b3f1..994c60a857ce 100644 --- a/arch/powerpc/include/asm/code-patching.h +++ b/arch/powerpc/include/asm/code-patching.h @@ -99,4 +99,25 @@ static inline unsigned long ppc_global_function_entry(void *func) #endif } +#ifdef CONFIG_PPC64 +/* + * Some instruction encodings commonly used in dynamic ftracing + * and function live patching. + */ + +/* This must match the definition of STK_GOT in */ +#if defined(_CALL_ELF) && _CALL_ELF == 2 +#define R2_STACK_OFFSET 24 +#else +#define R2_STACK_OFFSET 40 +#endif + +#define PPC_INST_LD_TOC (PPC_INST_LD | ___PPC_RT(__REG_R2) | \ + ___PPC_RA(__REG_R1) | R2_STACK_OFFSET) + +/* usually preceded by a mflr r0 */ +#define PPC_INST_STD_LR (PPC_INST_STD | ___PPC_RS(__REG_R0) | \ + ___PPC_RA(__REG_R1) | PPC_LR_STKOFF) +#endif /* CONFIG_PPC64 */ + #endif /* _ASM_POWERPC_CODE_PATCHING_H */ -- cgit v1.2.3