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Commit dbeb90b0 authored by Mao Han's avatar Mao Han Committed by Paul Walmsley
Browse files

riscv: Add perf callchain support 



This patch add support for perf callchain sampling on riscv platforms.
The return address of leaf function is retrieved from pt_regs as
it is not saved in the outmost frame.

Signed-off-by: default avatarMao Han <han_mao@c-sky.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: linux-riscv <linux-riscv@lists.infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Guo Ren <guoren@kernel.org>
Tested-by: default avatarGreentime Hu <greentime.hu@sifive.com>
[paul.walmsley@sifive.com: fixed some 'checkpatch.pl --strict' issues;
 fixed patch description spelling]
Signed-off-by: default avatarPaul Walmsley <paul.walmsley@sifive.com>
parent 909548d6

arch/riscv/Makefile

+3 −0
Original line number Original line Diff line number Diff line
@@ -54,6 +54,9 @@ endif 
ifeq ($(CONFIG_MODULE_SECTIONS),y)

ifeq ($(CONFIG_MODULE_SECTIONS),y)

	KBUILD_LDFLAGS_MODULE += -T $(srctree)/arch/riscv/kernel/module.lds

	KBUILD_LDFLAGS_MODULE += -T $(srctree)/arch/riscv/kernel/module.lds

endif

endif

ifeq ($(CONFIG_PERF_EVENTS),y)

        KBUILD_CFLAGS += -fno-omit-frame-pointer

endif





KBUILD_CFLAGS_MODULE += $(call cc-option,-mno-relax)

KBUILD_CFLAGS_MODULE += $(call cc-option,-mno-relax)

arch/riscv/kernel/Makefile

+2 −1
Original line number Original line Diff line number Diff line
@@ -39,5 +39,6 @@ obj-$(CONFIG_FUNCTION_TRACER) += mcount.o ftrace.o 
obj-$(CONFIG_DYNAMIC_FTRACE)	+= mcount-dyn.o

obj-$(CONFIG_DYNAMIC_FTRACE)	+= mcount-dyn.o





obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o

obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o

obj-$(CONFIG_PERF_EVENTS)	+= perf_callchain.o





clean:
 
clean:

arch/riscv/kernel/perf_callchain.c

0 → 100644
+94 −0
Original line number Original line Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/* Copyright (C) 2019 Hangzhou C-SKY Microsystems co.,ltd. */



#include <linux/perf_event.h>

#include <linux/uaccess.h>



/* Kernel callchain */

struct stackframe {

	unsigned long fp;

	unsigned long ra;

};



/*

 * Get the return address for a single stackframe and return a pointer to the

 * next frame tail.

 */

static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,

				    unsigned long fp, unsigned long reg_ra)

{

	struct stackframe buftail;

	unsigned long ra = 0;

	unsigned long *user_frame_tail =

			(unsigned long *)(fp - sizeof(struct stackframe));



	/* Check accessibility of one struct frame_tail beyond */

	if (!access_ok(user_frame_tail, sizeof(buftail)))

		return 0;

	if (__copy_from_user_inatomic(&buftail, user_frame_tail,

				      sizeof(buftail)))

		return 0;



	if (reg_ra != 0)

		ra = reg_ra;

	else

		ra = buftail.ra;



	fp = buftail.fp;

	if (ra != 0)

		perf_callchain_store(entry, ra);

	else

		return 0;



	return fp;

}



/*

 * This will be called when the target is in user mode

 * This function will only be called when we use

 * "PERF_SAMPLE_CALLCHAIN" in

 * kernel/events/core.c:perf_prepare_sample()

 *

 * How to trigger perf_callchain_[user/kernel] :

 * $ perf record -e cpu-clock --call-graph fp ./program

 * $ perf report --call-graph

 *

 * On RISC-V platform, the program being sampled and the C library

 * need to be compiled with -fno-omit-frame-pointer, otherwise

 * the user stack will not contain function frame.

 */

void perf_callchain_user(struct perf_callchain_entry_ctx *entry,

			 struct pt_regs *regs)

{

	unsigned long fp = 0;



	/* RISC-V does not support perf in guest mode. */

	if (perf_guest_cbs && perf_guest_cbs->is_in_guest())

		return;



	fp = regs->s0;

	perf_callchain_store(entry, regs->sepc);



	fp = user_backtrace(entry, fp, regs->ra);

	while (fp && !(fp & 0x3) && entry->nr < entry->max_stack)

		fp = user_backtrace(entry, fp, 0);

}



bool fill_callchain(unsigned long pc, void *entry)

{

	return perf_callchain_store(entry, pc);

}



void notrace walk_stackframe(struct task_struct *task,

	struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg);

void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,

			   struct pt_regs *regs)

{

	/* RISC-V does not support perf in guest mode. */

	if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {

		pr_warn("RISC-V does not support perf in guest mode!");

		return;

	}



	walk_stackframe(NULL, regs, fill_callchain, entry);

}

arch/riscv/kernel/stacktrace.c

+2 −2
Original line number Original line Diff line number Diff line
@@ -19,8 +19,8 @@ struct stackframe { 
	unsigned long ra;

	unsigned long ra;

};

};





static void notrace walk_stackframe(struct task_struct *task,

void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,

	struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg)

			     bool (*fn)(unsigned long, void *), void *arg)

{

{

	unsigned long fp, sp, pc;

	unsigned long fp, sp, pc;