[ A while ago I posted an RFC patchset for dynamic function based events. But Masami pointed out that this could be done with kprobes with minimal changes. He posted a patch set back in March http://lkml.kernel.org/r/152049860385.7289.14079393589900496424.stgit@devbox I've pulled this in locally, but haven't had the time until recently to look at it seriously. I even plan to talk about these changes in my talk at Open Source Summit in Edinburgh less than two weeks away (talk about conference driven development!). Anyway, the one patch that really needs external approval is the one that creates a new architecture dependent API to retrieve function arguments from pt_regs if the ip is at the start of the function call (via a breakpoint or ftrace fentry). That's this patch.
Anyone have any issues with it? If not, I'm going to start doing some serious testing of this code and try to get it into the next merge window. Thanks! -- Steve ] From: Masami Hiramatsu <mhira...@kernel.org> Add regs_get_argument() which returns N th argument of the function call. Note that this chooses most probably assignment, in some case it can be incorrect (e.g. passing data structure or floating point etc.) This is expected to be called from kprobes or ftrace with regs where the top of stack is the return address. Link: http://lkml.kernel.org/r/152465885737.26224.2822487520472783854.stgit@devbox Signed-off-by: Masami Hiramatsu <mhira...@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org> --- arch/Kconfig | 7 +++++++ arch/x86/Kconfig | 1 + arch/x86/include/asm/ptrace.h | 38 +++++++++++++++++++++++++++++++++++ 3 files changed, 46 insertions(+) diff --git a/arch/Kconfig b/arch/Kconfig index 6801123932a5..facace0c90fc 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -290,6 +290,13 @@ config HAVE_RSEQ This symbol should be selected by an architecture if it supports an implementation of restartable sequences. +config HAVE_FUNCTION_ARG_ACCESS_API + bool + help + This symbol should be selected by an architecure if it supports + the API needed to access function arguments from pt_regs, + declared in asm/ptrace.h + config HAVE_CLK bool help diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 1a0be022f91d..972973851779 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -184,6 +184,7 @@ config X86 select HAVE_RCU_TABLE_INVALIDATE if HAVE_RCU_TABLE_FREE select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_RELIABLE_STACKTRACE if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION + select HAVE_FUNCTION_ARG_ACCESS_API select HAVE_STACKPROTECTOR if CC_HAS_SANE_STACKPROTECTOR select HAVE_STACK_VALIDATION if X86_64 select HAVE_RSEQ diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h index 6de1fd3d0097..c2304b25e2fd 100644 --- a/arch/x86/include/asm/ptrace.h +++ b/arch/x86/include/asm/ptrace.h @@ -256,6 +256,44 @@ static inline unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs, return 0; } +/** + * regs_get_kernel_argument() - get Nth function argument in kernel + * @regs: pt_regs of that context + * @n: function argument number (start from 0) + * + * regs_get_argument() returns @n th argument of the function call. + * Note that this chooses most probably assignment, in some case + * it can be incorrect. + * This is expected to be called from kprobes or ftrace with regs + * where the top of stack is the return address. + */ +static inline unsigned long regs_get_kernel_argument(struct pt_regs *regs, + unsigned int n) +{ + static const unsigned int argument_offs[] = { +#ifdef __i386__ + offsetof(struct pt_regs, ax), + offsetof(struct pt_regs, cx), + offsetof(struct pt_regs, dx), +#define NR_REG_ARGUMENTS 3 +#else + offsetof(struct pt_regs, di), + offsetof(struct pt_regs, si), + offsetof(struct pt_regs, dx), + offsetof(struct pt_regs, cx), + offsetof(struct pt_regs, r8), + offsetof(struct pt_regs, r9), +#define NR_REG_ARGUMENTS 6 +#endif + }; + + if (n >= NR_REG_ARGUMENTS) { + n -= NR_REG_ARGUMENTS - 1; + return regs_get_kernel_stack_nth(regs, n); + } else + return regs_get_register(regs, argument_offs[n]); +} + #define arch_has_single_step() (1) #ifdef CONFIG_X86_DEBUGCTLMSR #define arch_has_block_step() (1) -- 2.19.0
