Messages in this thread | | | Date | Wed, 3 Apr 2019 13:06:49 +0100 | From | Will Deacon <> | Subject | Re: [PATCH] arm64: ptrace: Add function argument access API |
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On Mon, Mar 18, 2019 at 04:59:02PM +0900, Masami Hiramatsu wrote: > 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 <mhiramat@kernel.org> > --- > arch/arm64/Kconfig | 1 + > arch/arm64/include/asm/ptrace.h | 18 ++++++++++++++++++ > 2 files changed, 19 insertions(+) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 117b2541ef3d..6ba0da4be73c 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..cfa1bc9b8b70 100644 > --- a/arch/arm64/include/asm/ptrace.h > +++ b/arch/arm64/include/asm/ptrace.h > @@ -305,6 +305,24 @@ 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 most probably assignment, in some case > + * it can be incorrect.
In which cases would it be incorrect? I can imagine varargs causing problems, but are there others?
> +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 regs_get_register(regs, n << 3);
You can use pt_regs_read_reg() to avoid the shift here.
Will
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