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Message-ID: <87wmm2y22u.fsf@all.your.base.are.belong.to.us>
Date: Wed, 03 Jul 2024 16:36:41 +0200
From: Björn Töpel <bjorn@...nel.org>
To: Jinjie Ruan <ruanjinjie@...wei.com>, 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
Cc: ruanjinjie@...wei.com
Subject: Re: [PATCH v2] riscv: stacktrace: Add USER_STACKTRACE support
Jinjie Ruan <ruanjinjie@...wei.com> writes:
> 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().
>
> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202406012109.PDAjXm2i-lkp@intel.com/
For future reference: The LTP tags shouldn't be used when you're
spinning a new version.
> ---
> 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 0525ee2d63c7..6ed96d935b8f 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -193,6 +193,7 @@ 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 3348a61de7d9..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 & 0x3) && 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 528ec7cc9a62..9685a2baa5d9 100644
> --- a/arch/riscv/kernel/stacktrace.c
> +++ b/arch/riscv/kernel/stacktrace.c
> @@ -161,3 +161,46 @@ noinline void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie
> {
> 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 & 0x3))
Just an observation that the "entry->nr < entry->max_stack" check was
removed in this generalization, but that's OK since it's checked in
perf_callchain_store().
Not really part of your change, but shouldn't the check be 0x7 (checking
for 16B sp/fp alignment), rather than 0x3?
Björn
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