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From: Steven Rostedt <rostedt@goodmis.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Wang ShaoBo <bobo.shaobowang@huawei.com>,
	cj.chengjian@huawei.com, huawei.libin@huawei.com,
	xiexiuqi@huawei.com, liwei391@huawei.com,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com,
	will@kernel.org, zengshun.wu@outlook.com,
	Masami Hiramatsu <mhiramat@kernel.org>
Subject: Re: [RFC PATCH -next v2 3/4] arm64/ftrace: support dynamically allocated trampolines
Date: Fri, 22 Apr 2022 11:45:41 -0400	[thread overview]
Message-ID: <20220422114541.34d71ad9@gandalf.local.home> (raw)
In-Reply-To: <YmJ/l4vJoEpFt68l@FVFF77S0Q05N>

On Fri, 22 Apr 2022 11:12:39 +0100
Mark Rutland <mark.rutland@arm.com> wrote:

> As an aside, I'd also love to remove the REGS/!REGs distinction, and always
> save a minimum amount of state (like ARGS, but never saving a full pt_regs),
> since on arm64 the extra state stored for the REGS case isn't useful (and we
> can't reliably capture all of the pt_regs state anyway, so bits of it are made
> up or not filled in).

Note, the reason for the addition of REGS was a requirement of kprobes.
Because before ftrace, kprobes would be triggered at the start of a
function by a breakpoint that would load in all the regs. And for backward
compatibility, Masami wanted to make sure that kprobes coming from ftrace
had all the regs just like it had when coming from a breakpoint.

IIUC, kprobes is the only reason we have the "regs" variant (all other use
cases could get by with the ARGS version).

-- Steve

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  reply	other threads:[~2022-04-22 15:50 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-16 10:01 [RFC PATCH -next v2 0/4] arm64/ftrace: support dynamic trampoline Wang ShaoBo
2022-03-16 10:01 ` [RFC PATCH -next v2 1/4] arm64: introduce aarch64_insn_gen_load_literal Wang ShaoBo
2022-03-16 10:01 ` [RFC PATCH -next v2 2/4] arm64/ftrace: introduce ftrace dynamic trampoline entrances Wang ShaoBo
2022-03-16 10:01 ` [RFC PATCH -next v2 3/4] arm64/ftrace: support dynamically allocated trampolines Wang ShaoBo
2022-04-21 13:10   ` Mark Rutland
2022-04-21 14:06     ` Steven Rostedt
2022-04-21 14:08       ` Steven Rostedt
2022-04-21 15:14       ` Mark Rutland
2022-04-21 15:42         ` Steven Rostedt
2022-04-21 16:27           ` Mark Rutland
2022-04-21 17:06             ` Steven Rostedt
2022-04-22 10:12               ` Mark Rutland
2022-04-22 15:45                 ` Steven Rostedt [this message]
2022-04-22 17:27                   ` Mark Rutland
2022-04-26  8:47                     ` Masami Hiramatsu
2022-05-04 10:24                       ` Mark Rutland
2022-05-05  3:15                         ` Masami Hiramatsu
2022-05-09 18:22                           ` Steven Rostedt
2022-05-10  9:10                             ` Masami Hiramatsu
2022-05-10 14:44                               ` Steven Rostedt
2022-05-11 14:34                                 ` Masami Hiramatsu
2022-05-11 15:12                                   ` Steven Rostedt
2022-05-12 12:02                                     ` Masami Hiramatsu
2022-05-12 13:50                                       ` Steven Rostedt
2022-05-25 12:17                                       ` Mark Rutland
2022-05-25 13:43                                         ` Steven Rostedt
2022-05-25 17:12                                           ` Mark Rutland
2022-05-30  1:03                                         ` Masami Hiramatsu
2022-05-30 12:38                                           ` Jiri Olsa
2022-05-31  1:00                                             ` Masami Hiramatsu
2022-05-04 12:43               ` Mark Rutland
2022-05-05  2:57             ` Wangshaobo (bobo)
2022-05-25 12:27               ` Mark Rutland
2022-04-27  8:54       ` Wangshaobo (bobo)
2022-03-16 10:01 ` [RFC PATCH -next v2 4/4] arm64/ftrace: implement long jump for dynamic trampolines Wang ShaoBo
2022-04-21 13:47   ` Mark Rutland
2022-03-16 14:29 ` [RFC PATCH -next v2 0/4] arm64/ftrace: support dynamic trampoline Steven Rostedt
2022-04-20 18:11 ` Steven Rostedt
2022-04-21  1:13   ` Wangshaobo (bobo)
2022-04-21 12:37     ` Steven Rostedt
2022-05-25 12:45       ` Mark Rutland
2022-05-25 13:58         ` Steven Rostedt
2022-05-25 17:26           ` Mark Rutland
2022-04-21 12:53 ` Mark Rutland

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