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x86: ptrace: Add function argument access API

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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: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Masami Hiramatsu 2018-04-25 21:20:57 +09:00 committed by Steven Rostedt (VMware)
parent 40b53b7718
commit 3c88ee194c
3 changed files with 46 additions and 0 deletions
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7
arch/Kconfig
View File

@ -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

1
arch/x86/Kconfig
View File

@ -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

38
arch/x86/include/asm/ptrace.h
View File

@ -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)