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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>
This commit is contained in:
Qing Zhang 2023-02-25 15:52:57 +08:00 committed by Huacai Chen
parent 1a69f7a161
commit 356bd6f236
2 changed files with 35 additions and 0 deletions
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1
arch/loongarch/Kconfig
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@ -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

34
arch/loongarch/include/asm/ptrace.h
View File

@ -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?
*/