Commit 8564c315 authored by Florent Revest's avatar Florent Revest Committed by Steven Rostedt (Google)
Browse files

samples: ftrace: Save required argument registers in sample trampolines 

The ftrace-direct-too sample traces the handle_mm_fault function whose
signature changed since the introduction of the sample. Since:
commit bce617ed ("mm: do page fault accounting in handle_mm_fault")
handle_mm_fault now has 4 arguments. Therefore, the sample trampoline
should save 4 argument registers.

s390 saves all argument registers already so it does not need a change
but x86_64 needs an extra push and pop.

This also evolves the signature of the tracing function to make it
mirror the signature of the traced function.

Link: https://lkml.kernel.org/r/20230427140700.625241-2-revest@chromium.org



Cc: stable@vger.kernel.org
Fixes: bce617ed ("mm: do page fault accounting in handle_mm_fault")
Reviewed-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarFlorent Revest <revest@chromium.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 06c2afb8

samples/ftrace/ftrace-direct-too.c

+8 −6
Original line number Diff line number Diff line
@@ -5,14 +5,14 @@ 
#include <linux/ftrace.h>

#include <asm/asm-offsets.h>



extern void my_direct_func(struct vm_area_struct *vma,

			   unsigned long address, unsigned int flags);

extern void my_direct_func(struct vm_area_struct *vma, unsigned long address,

			   unsigned int flags, struct pt_regs *regs);



void my_direct_func(struct vm_area_struct *vma,

			unsigned long address, unsigned int flags)

void my_direct_func(struct vm_area_struct *vma, unsigned long address,

		    unsigned int flags, struct pt_regs *regs)

{

	trace_printk("handle mm fault vma=%p address=%lx flags=%x\n",

		     vma, address, flags);

	trace_printk("handle mm fault vma=%p address=%lx flags=%x regs=%p\n",

		     vma, address, flags, regs);

}



extern void my_tramp(void *);
@@ -34,7 +34,9 @@ asm ( 
"	pushq %rdi\n"

"	pushq %rsi\n"

"	pushq %rdx\n"

"	pushq %rcx\n"

"	call my_direct_func\n"

"	popq %rcx\n"

"	popq %rdx\n"

"	popq %rsi\n"

"	popq %rdi\n"