From a823c35ff2eda73046cc1847326071de350fceda Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Fri, 12 Apr 2019 23:22:01 +0900 Subject: [PATCH] arm64: ptrace: Add function argument access API Add regs_get_argument() which returns N th argument of the function call. On arm64, it supports up to 8th argument. Note that this chooses most probably assignment, in some case it can be incorrect (e.g. passing data structure or floating point etc.) This enables ftrace kprobe events to access kernel function arguments via $argN syntax. Signed-off-by: Masami Hiramatsu [will: tidied up the comment a bit] Signed-off-by: Will Deacon --- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/ptrace.h | 22 ++++++++++++++++++++++ 2 files changed, 23 insertions(+) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 555af5035592..c383625ec02c 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -148,6 +148,7 @@ config ARM64 select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP select HAVE_REGS_AND_STACK_ACCESS_API + select HAVE_FUNCTION_ARG_ACCESS_API select HAVE_RCU_TABLE_FREE select HAVE_RCU_TABLE_INVALIDATE select HAVE_RSEQ diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h index ec60174c8c18..b2de32939ada 100644 --- a/arch/arm64/include/asm/ptrace.h +++ b/arch/arm64/include/asm/ptrace.h @@ -305,6 +305,28 @@ static inline unsigned long regs_return_value(struct pt_regs *regs) return regs->regs[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 the most likely register mapping. In very rare + * cases this may not return correct data, for example, if one of the + * function parameters is 16 bytes or bigger. In such cases, we cannot + * get access the parameter correctly and the register assignment of + * subsequent parameters will be shifted. + */ +static inline unsigned long regs_get_kernel_argument(struct pt_regs *regs, + unsigned int n) +{ +#define NR_REG_ARGUMENTS 8 + if (n < NR_REG_ARGUMENTS) + return pt_regs_read_reg(regs, n); + return 0; +} + /* We must avoid circular header include via sched.h */ struct task_struct; int valid_user_regs(struct user_pt_regs *regs, struct task_struct *task);