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Message-ID: <cff7274d-e423-9ac9-7d15-cedad7d85701@huawei.com>
Date: Tue, 23 Jul 2024 09:40:21 +0800
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: <bjorn@...nel.org>, <paul.walmsley@...ive.com>, <palmer@...belt.com>,
<aou@...s.berkeley.edu>, <peterz@...radead.org>, <mingo@...hat.com>,
<acme@...nel.org>, <namhyung@...nel.org>, <mark.rutland@....com>,
<alexander.shishkin@...ux.intel.com>, <jolsa@...nel.org>,
<irogers@...gle.com>, <adrian.hunter@...el.com>, <kan.liang@...ux.intel.com>,
<dev.mbstr@...il.com>, <samuel.holland@...ive.com>,
<linux-riscv@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
<linux-perf-users@...r.kernel.org>
Subject: Re: [PATCH v3 2/2] riscv: stacktrace: Add USER_STACKTRACE support
On 2024/7/8 11:28, Jinjie Ruan wrote:
> 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
Gentle ping.
>
> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
> Tested-by: Jinjie Ruan <ruanjinjie@...wei.com>
> Cc: Björn Töpel <bjorn@...nel.org>
> ---
> v3:
> - Remove the LTP message as Björn suggested.
> - Keep fp 16-bytes aligned in arch_stack_walk_user().
> - Add the test info.
> v2:
> - Fix the cocci warning, !A || A && B is equivalent to !A || B.
> ---
> ---
> arch/riscv/Kconfig | 1 +
> arch/riscv/kernel/perf_callchain.c | 46 ++----------------------------
> arch/riscv/kernel/stacktrace.c | 43 ++++++++++++++++++++++++++++
> 3 files changed, 47 insertions(+), 43 deletions(-)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 3b44e7b51436..46121dbcf750 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -194,6 +194,7 @@ 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
> diff --git a/arch/riscv/kernel/perf_callchain.c b/arch/riscv/kernel/perf_callchain.c
> index 2932791e9388..c7468af77c66 100644
> --- a/arch/riscv/kernel/perf_callchain.c
> +++ b/arch/riscv/kernel/perf_callchain.c
> @@ -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,
> diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
> index 0d3f00eb0bae..5480cc11b523 100644
> --- a/arch/riscv/kernel/stacktrace.c
> +++ b/arch/riscv/kernel/stacktrace.c
> @@ -161,3 +161,46 @@ 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);
> +}
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