From: Heiko Carstens <hca@linux.ibm.com>
To: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Florent Revest <revest@chromium.org>,
linux-trace-kernel@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
bpf <bpf@vger.kernel.org>, Sven Schnelle <svens@linux.ibm.com>,
Alexei Starovoitov <ast@kernel.org>, Jiri Olsa <jolsa@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Alan Maguire <alan.maguire@oracle.com>,
Mark Rutland <mark.rutland@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>, Guo Ren <guoren@kernel.org>,
linux-arch@vger.kernel.org
Subject: Re: [PATCH v15 09/19] tracing: Add ftrace_fill_perf_regs() for perf event
Date: Wed, 9 Oct 2024 12:05:02 +0200 [thread overview]
Message-ID: <20241009100502.8007-E-hca@linux.ibm.com> (raw)
In-Reply-To: <172639147435.366111.834128908630424679.stgit@devnote2>
On Sun, Sep 15, 2024 at 06:11:14PM +0900, Masami Hiramatsu (Google) wrote:
> From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>
> Add ftrace_fill_perf_regs() which should be compatible with the
> perf_fetch_caller_regs(). In other words, the pt_regs returned from the
> ftrace_fill_perf_regs() must satisfy 'user_mode(regs) == false' and can be
> used for stack tracing.
>
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
...
> arch/s390/include/asm/ftrace.h | 5 +++++
...
> diff --git a/arch/s390/include/asm/ftrace.h b/arch/s390/include/asm/ftrace.h
> index 9cdd48a46bf7..0d9f6df21f81 100644
> --- a/arch/s390/include/asm/ftrace.h
> +++ b/arch/s390/include/asm/ftrace.h
> @@ -84,6 +84,11 @@ ftrace_regs_get_frame_pointer(struct ftrace_regs *fregs)
> return sp[0]; /* return backchain */
> }
>
> +#define arch_ftrace_fill_perf_regs(fregs, _regs) do { \
> + (_regs)->psw.addr = (fregs)->regs.psw.addr; \
> + (_regs)->gprs[15] = (fregs)->regs.gprs[15]; \
> + } while (0)
After reading your commit description and looking at the code I think the
s390 implementation of perf_arch_fetch_caller_regs() is at least
suboptimal: it is not possible to tell if an address belongs to user or
kernel space by looking only at the address (psw.addr); this also requires
to look at psw.mask. It _looks_ like all current callers of
perf_arch_fetch_caller_regs() initialize the passed in pt_regs to zero,
which of course also sets psw.mask to zero, and therefore
user_mode(regs) == false is satisfied.
However I'd rather make that explicit and don't want to rely on
callers. Therefore the above arch_ftrace_fill_perf_regs() should
set the mask to zero
(_regs)->psw.mask = 0;
I will change perf_arch_fetch_caller_regs() accordingly.
next prev parent reply other threads:[~2024-10-09 10:05 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-15 9:09 [PATCH v15 00/19] tracing: fprobe: function_graph: Multi-function graph and fprobe on fgraph Masami Hiramatsu (Google)
2024-09-15 9:09 ` [PATCH v15 01/19] tracing: Add a comment about ftrace_regs definition Masami Hiramatsu (Google)
2024-09-15 9:09 ` [PATCH v15 02/19] tracing: Rename ftrace_regs_return_value to ftrace_regs_get_return_value Masami Hiramatsu (Google)
2024-09-15 9:10 ` [PATCH v15 03/19] function_graph: Pass ftrace_regs to entryfunc Masami Hiramatsu (Google)
2024-09-15 9:10 ` [PATCH v15 04/19] function_graph: Replace fgraph_ret_regs with ftrace_regs Masami Hiramatsu (Google)
2024-09-15 9:10 ` [PATCH v15 05/19] function_graph: Pass ftrace_regs to retfunc Masami Hiramatsu (Google)
2024-09-15 9:10 ` [PATCH v15 06/19] fprobe: Use ftrace_regs in fprobe entry handler Masami Hiramatsu (Google)
2024-09-15 9:10 ` [PATCH v15 07/19] fprobe: Use ftrace_regs in fprobe exit handler Masami Hiramatsu (Google)
2024-09-15 9:11 ` [PATCH v15 08/19] tracing: Add ftrace_partial_regs() for converting ftrace_regs to pt_regs Masami Hiramatsu (Google)
2024-09-15 9:11 ` [PATCH v15 09/19] tracing: Add ftrace_fill_perf_regs() for perf event Masami Hiramatsu (Google)
2024-10-09 10:05 ` Heiko Carstens [this message]
2024-09-15 9:11 ` [PATCH v15 10/19] tracing/fprobe: Enable fprobe events with CONFIG_DYNAMIC_FTRACE_WITH_ARGS Masami Hiramatsu (Google)
2024-09-15 9:11 ` [PATCH v15 11/19] bpf: Enable kprobe_multi feature if CONFIG_FPROBE is enabled Masami Hiramatsu (Google)
2024-09-15 9:11 ` [PATCH v15 12/19] ftrace: Add CONFIG_HAVE_FTRACE_GRAPH_FUNC Masami Hiramatsu (Google)
2024-09-15 9:12 ` [PATCH v15 13/19] fprobe: Rewrite fprobe on function-graph tracer Masami Hiramatsu (Google)
2024-09-23 8:08 ` Sven Schnelle
2024-09-15 9:12 ` [PATCH v15 14/19] tracing: Fix function timing profiler to initialize hashtable Masami Hiramatsu (Google)
2024-09-15 9:12 ` [PATCH v15 15/19] tracing/fprobe: Remove nr_maxactive from fprobe Masami Hiramatsu (Google)
2024-09-15 9:12 ` [PATCH v15 16/19] selftests: ftrace: Remove obsolate maxactive syntax check Masami Hiramatsu (Google)
2024-09-15 9:12 ` [PATCH v15 17/19] selftests/ftrace: Add a test case for repeating register/unregister fprobe Masami Hiramatsu (Google)
2024-09-15 9:12 ` [PATCH v15 18/19] Documentation: probes: Update fprobe on function-graph tracer Masami Hiramatsu (Google)
2024-09-15 9:13 ` [PATCH v15 19/19] bpf: Add get_entry_ip() for arm64 Masami Hiramatsu (Google)
2024-09-18 21:22 ` [PATCH v15 00/19] tracing: fprobe: function_graph: Multi-function graph and fprobe on fgraph Andrii Nakryiko
2024-09-20 11:26 ` Masami Hiramatsu
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