Commit 3c88ee19 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Steven Rostedt (VMware)
Browse files

x86: ptrace: Add function argument access API 

Add regs_get_argument() which returns N th argument of the
function call.
Note that this chooses most probably assignment, in some case
it can be incorrect (e.g. passing data structure or floating
point etc.)

This is expected to be called from kprobes or ftrace with regs
where the top of stack is the return address.

Link: http://lkml.kernel.org/r/152465885737.26224.2822487520472783854.stgit@devbox



Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 40b53b77

arch/Kconfig

+7 −0
Original line number Diff line number Diff line
@@ -290,6 +290,13 @@ config HAVE_RSEQ 
	  This symbol should be selected by an architecture if it

	  supports an implementation of restartable sequences.



config HAVE_FUNCTION_ARG_ACCESS_API

	bool

	help

	  This symbol should be selected by an architecure if it supports

	  the API needed to access function arguments from pt_regs,

	  declared in asm/ptrace.h



config HAVE_CLK

	bool

	help

arch/x86/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -184,6 +184,7 @@ config X86 
	select HAVE_RCU_TABLE_INVALIDATE	if HAVE_RCU_TABLE_FREE

	select HAVE_REGS_AND_STACK_ACCESS_API

	select HAVE_RELIABLE_STACKTRACE		if X86_64 && (UNWINDER_FRAME_POINTER || UNWINDER_ORC) && STACK_VALIDATION

	select HAVE_FUNCTION_ARG_ACCESS_API

	select HAVE_STACKPROTECTOR		if CC_HAS_SANE_STACKPROTECTOR

	select HAVE_STACK_VALIDATION		if X86_64

	select HAVE_RSEQ

arch/x86/include/asm/ptrace.h

+38 −0
Original line number Diff line number Diff line
@@ -256,6 +256,44 @@ static inline unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs, 
		return 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.

 * 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[] = {

#ifdef __i386__

		offsetof(struct pt_regs, ax),

		offsetof(struct pt_regs, cx),

		offsetof(struct pt_regs, dx),

#define NR_REG_ARGUMENTS 3

#else

		offsetof(struct pt_regs, di),

		offsetof(struct pt_regs, si),

		offsetof(struct pt_regs, dx),

		offsetof(struct pt_regs, cx),

		offsetof(struct pt_regs, r8),

		offsetof(struct pt_regs, r9),

#define NR_REG_ARGUMENTS 6

#endif

	};



	if (n >= NR_REG_ARGUMENTS) {

		n -= NR_REG_ARGUMENTS - 1;

		return regs_get_kernel_stack_nth(regs, n);

	} else

		return regs_get_register(regs, argument_offs[n]);

}



#define arch_has_single_step()	(1)

#ifdef CONFIG_X86_DEBUGCTLMSR

#define arch_has_block_step()	(1)

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