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| author | Qing Zhang <zhangqing@loongson.cn> | 2023-02-25 15:52:57 +0800 |
|---|---|---|
| committer | Huacai Chen <chenhuacai@loongson.cn> | 2023-02-25 22:12:17 +0800 |
| commit | 356bd6f23682f11f7afe923d86c7f5f852b97fb2 (patch) | |
| tree | ec88f7e3445613d5e304f22d3f6e9840f88139ef | |
| parent | 1a69f7a161a78aead07cd4b811d796950e892fa4 (diff) | |
| download | lwn-356bd6f23682f11f7afe923d86c7f5f852b97fb2.tar.gz lwn-356bd6f23682f11f7afe923d86c7f5f852b97fb2.zip | |
LoongArch: ptrace: Add function argument access API
Add regs_get_argument() which returns N th argument of the function
call, This enables ftrace kprobe events to access kernel function
arguments via $argN syntax for later use.
E.g.:
echo 'p bio_add_page arg1=$arg1' > kprobe_events
bash: echo: write error: Invalid argument
Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
| -rw-r--r-- | arch/loongarch/Kconfig | 1 | ||||
| -rw-r--r-- | arch/loongarch/include/asm/ptrace.h | 34 |
2 files changed, 35 insertions, 0 deletions
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig index 97423f86384b..277ce9b9414e 100644 --- a/arch/loongarch/Kconfig +++ b/arch/loongarch/Kconfig @@ -98,6 +98,7 @@ config LOONGARCH select HAVE_EXIT_THREAD select HAVE_FAST_GUP select HAVE_FTRACE_MCOUNT_RECORD + select HAVE_FUNCTION_ARG_ACCESS_API select HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_TRACER select HAVE_GENERIC_VDSO diff --git a/arch/loongarch/include/asm/ptrace.h b/arch/loongarch/include/asm/ptrace.h index 59c4608de91d..5d3872131866 100644 --- a/arch/loongarch/include/asm/ptrace.h +++ b/arch/loongarch/include/asm/ptrace.h @@ -109,6 +109,40 @@ static inline unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs, unsi struct task_struct; +/** + * 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) +{ +#define NR_REG_ARGUMENTS 8 + static const unsigned int args[] = { + offsetof(struct pt_regs, regs[4]), + offsetof(struct pt_regs, regs[5]), + offsetof(struct pt_regs, regs[6]), + offsetof(struct pt_regs, regs[7]), + offsetof(struct pt_regs, regs[8]), + offsetof(struct pt_regs, regs[9]), + offsetof(struct pt_regs, regs[10]), + offsetof(struct pt_regs, regs[11]), + }; + + if (n < NR_REG_ARGUMENTS) + return regs_get_register(regs, args[n]); + else { + n -= NR_REG_ARGUMENTS; + return regs_get_kernel_stack_nth(regs, n); + } +} + /* * Does the process account for user or for system time? */ |