Add regs_get_argument() which returns N th argument of the function
call, t show This enables ftrace kprobe events to access kernel function
arguments via $argN syntax.
eg:
echo 'p bio_add_page arg1=$arg1' > kprobe_events
bash: echo: write error: Invalid argument
Signed-off-by: Qing Zhang <[email protected]>
---
arch/loongarch/Kconfig | 1 +
arch/loongarch/include/asm/ptrace.h | 33 +++++++++++++++++++++++++++++
2 files changed, 34 insertions(+)
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index e3eba2eb4b44..103046966893 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -97,6 +97,7 @@ 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 66a0e6c480a3..f6ffcc00753c 100644
--- a/arch/loongarch/include/asm/ptrace.h
+++ b/arch/loongarch/include/asm/ptrace.h
@@ -120,6 +120,39 @@ static inline long regs_return_value(struct pt_regs *regs)
return regs->regs[4];
}
+/**
+ * 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[] = {
+ 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]),
+#define NR_REG_ARGUMENTS 8
+ };
+
+ if (n >= NR_REG_ARGUMENTS) {
+ n -= NR_REG_ARGUMENTS;
+ return regs_get_kernel_stack_nth(regs, n);
+ } else
+ return regs_get_register(regs, argument_offs[n]);
+}
+
#define instruction_pointer(regs) ((regs)->csr_era)
#define profile_pc(regs) instruction_pointer(regs)
--
2.36.0
On Sat, Feb 11, 2023 at 4:44 PM Qing Zhang <[email protected]> wrote:
>
> Add regs_get_argument() which returns N th argument of the function
> call, t show This enables ftrace kprobe events to access kernel function
> arguments via $argN syntax.
Sadly, I think this message should be rewritten.
>
> eg:
> echo 'p bio_add_page arg1=$arg1' > kprobe_events
> bash: echo: write error: Invalid argument
>
> Signed-off-by: Qing Zhang <[email protected]>
> ---
> arch/loongarch/Kconfig | 1 +
> arch/loongarch/include/asm/ptrace.h | 33 +++++++++++++++++++++++++++++
> 2 files changed, 34 insertions(+)
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index e3eba2eb4b44..103046966893 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -97,6 +97,7 @@ 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 66a0e6c480a3..f6ffcc00753c 100644
> --- a/arch/loongarch/include/asm/ptrace.h
> +++ b/arch/loongarch/include/asm/ptrace.h
> @@ -120,6 +120,39 @@ static inline long regs_return_value(struct pt_regs *regs)
> return regs->regs[4];
> }
>
> +/**
> + * 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[] = {
> + 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]),
> +#define NR_REG_ARGUMENTS 8
> + };
> +
> + if (n >= NR_REG_ARGUMENTS) {
> + n -= NR_REG_ARGUMENTS;
> + return regs_get_kernel_stack_nth(regs, n);
> + } else
> + return regs_get_register(regs, argument_offs[n]);
> +}
> +
> #define instruction_pointer(regs) ((regs)->csr_era)
> #define profile_pc(regs) instruction_pointer(regs)
>
> --
> 2.36.0
>