Unverified Commit 1a748331 authored by Jinjie Ruan's avatar Jinjie Ruan Committed by Palmer Dabbelt
Browse files

riscv: stacktrace: Add USER_STACKTRACE support 



Currently, userstacktrace is unsupported for riscv. So use the
perf_callchain_user() code as blueprint to implement the
arch_stack_walk_user() which add userstacktrace support on riscv.
Meanwhile, we can use arch_stack_walk_user() to simplify the implementation
of perf_callchain_user().

A ftrace test case is shown as below:

	# cd /sys/kernel/debug/tracing
	# echo 1 > options/userstacktrace
	# echo 1 > options/sym-userobj
	# echo 1 > events/sched/sched_process_fork/enable
	# cat trace
	......
	            bash-178     [000] ...1.    97.968395: sched_process_fork: comm=bash pid=178 child_comm=bash child_pid=231
	            bash-178     [000] ...1.    97.970075: <user stack trace>
	 => /lib/libc.so.6[+0xb5090]

Also a simple perf test is ok as below:

	# perf record -e cpu-clock --call-graph fp top
	# perf report --call-graph

	.....
	[[31m  66.54%[[m     0.00%  top      [kernel.kallsyms]            [k] ret_from_exception
            |
            ---ret_from_exception
               |
               |--[[31m58.97%[[m--do_trap_ecall_u
               |          |
               |          |--[[31m17.34%[[m--__riscv_sys_read
               |          |          ksys_read
               |          |          |
               |          |           --[[31m16.88%[[m--vfs_read
               |          |                     |
               |          |                     |--[[31m10.90%[[m--seq_read

Signed-off-by: default avatarJinjie Ruan <ruanjinjie@huawei.com>
Tested-by: default avatarJinjie Ruan <ruanjinjie@huawei.com>
Cc: Björn Töpel <bjorn@kernel.org>
Link: https://lore.kernel.org/r/20240708032847.2998158-3-ruanjinjie@huawei.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent 22ab0895

arch/riscv/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -200,6 +200,7 @@ config RISCV 
	select THREAD_INFO_IN_TASK

	select TRACE_IRQFLAGS_SUPPORT

	select UACCESS_MEMCPY if !MMU

	select USER_STACKTRACE_SUPPORT

	select ZONE_DMA32 if 64BIT



config CLANG_SUPPORTS_DYNAMIC_FTRACE

arch/riscv/kernel/perf_callchain.c

+3 −43
Original line number Diff line number Diff line
@@ -6,37 +6,9 @@ 


#include <asm/stacktrace.h>



/*

 * 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)

static bool fill_callchain(void *entry, unsigned long pc)

{

	struct stackframe buftail;

	unsigned long ra = 0;

	unsigned long __user *user_frame_tail =

		(unsigned long __user *)(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;

	return perf_callchain_store(entry, pc) == 0;

}



/*
@@ -56,19 +28,7 @@ static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry, 
void perf_callchain_user(struct perf_callchain_entry_ctx *entry,

			 struct pt_regs *regs)

{

	unsigned long fp = 0;



	fp = regs->s0;

	perf_callchain_store(entry, regs->epc);



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

	while (fp && !(fp & 0x7) && entry->nr < entry->max_stack)

		fp = user_backtrace(entry, fp, 0);

}



static bool fill_callchain(void *entry, unsigned long pc)

{

	return perf_callchain_store(entry, pc) == 0;

	arch_stack_walk_user(fill_callchain, entry, regs);

}



void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,

arch/riscv/kernel/stacktrace.c

+43 −0
Original line number Diff line number Diff line
@@ -162,3 +162,46 @@ noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry, void 
{

	walk_stackframe(task, regs, consume_entry, cookie);

}



/*

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

 * next frame tail.

 */

static unsigned long unwind_user_frame(stack_trace_consume_fn consume_entry,

				       void *cookie, unsigned long fp,

				       unsigned long reg_ra)

{

	struct stackframe buftail;

	unsigned long ra = 0;

	unsigned long __user *user_frame_tail =

		(unsigned long __user *)(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;



	ra = reg_ra ? : buftail.ra;



	fp = buftail.fp;

	if (!ra || !consume_entry(cookie, ra))

		return 0;



	return fp;

}



void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,

			  const struct pt_regs *regs)

{

	unsigned long fp = 0;



	fp = regs->s0;

	if (!consume_entry(cookie, regs->epc))

		return;



	fp = unwind_user_frame(consume_entry, cookie, fp, regs->ra);

	while (fp && !(fp & 0x7))

		fp = unwind_user_frame(consume_entry, cookie, fp, 0);

}