Commit 356bd6f2 authored by Qing Zhang's avatar Qing Zhang Committed by Huacai Chen
Browse files

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: default avatarQing Zhang <zhangqing@loongson.cn>
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent 1a69f7a1

arch/loongarch/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/loongarch/include/asm/ptrace.h

+34 −0
Original line number Diff line number Diff line
@@ -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?

 */