From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [for-next][PATCH 04/18] x86/ftrace: Do not jump to direct code in created trampolines
Date: Fri, 3 Jul 2020 10:10:00 +0200 [thread overview]
Message-ID: <20200703081000.GT4800@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200702215832.049969400@goodmis.org>
On Thu, Jul 02, 2020 at 05:58:16PM -0400, Steven Rostedt wrote:
> + /* No need to test direct calls on created trampolines */
> + if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
> + /* NOP the jnz 1f; but make sure it's a 2 byte jnz */
> + ip = trampoline + (jmp_offset - start_offset);
> + if (WARN_ON(*(char *)ip != 0x75))
> + goto fail;
> + ret = copy_from_kernel_nofault(ip, ideal_nops[2], 2);
I really don't get this paranoia, what's wrong with memcpy() ?
> + if (ret < 0)
> + goto fail;
> + }
How about something like this?
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -359,17 +359,11 @@ create_trampoline(struct ftrace_ops *ops
npages = DIV_ROUND_UP(*tramp_size, PAGE_SIZE);
/* Copy ftrace_caller onto the trampoline memory */
- ret = copy_from_kernel_nofault(trampoline, (void *)start_offset, size);
- if (WARN_ON(ret < 0))
- goto fail;
-
- ip = trampoline + size;
+ memcpy(trampoline, (void *)start_offset, size);
/* The trampoline ends with ret(q) */
- retq = (unsigned long)ftrace_stub;
- ret = copy_from_kernel_nofault(ip, (void *)retq, RET_SIZE);
- if (WARN_ON(ret < 0))
- goto fail;
+ ip = trampoline + size;
+ memcpy(ip, text_gen_insn(RET_INSN_OPCODE, NULL, NULL), RET_INSN_SIZE);
/* No need to test direct calls on created trampolines */
if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
@@ -377,9 +371,7 @@ create_trampoline(struct ftrace_ops *ops
ip = trampoline + (jmp_offset - start_offset);
if (WARN_ON(*(char *)ip != 0x75))
goto fail;
- ret = copy_from_kernel_nofault(ip, ideal_nops[2], 2);
- if (ret < 0)
- goto fail;
+ memcpy(ip, ideal_nops[2], 2);
}
/*
next prev parent reply other threads:[~2020-07-03 8:10 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-02 21:58 [for-next][PATCH 00/18] tracing: Updatse for 5.9 Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 01/18] tracing: Only allow trace_array_printk() to be used by instances Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 02/18] x86/ftrace: Make non direct case the default in ftrace_regs_caller Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 03/18] x86/ftrace: Only have the builtin ftrace_regs_caller call direct hooks Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 04/18] x86/ftrace: Do not jump to direct code in created trampolines Steven Rostedt
2020-07-03 8:10 ` Peter Zijlstra [this message]
2020-07-14 3:24 ` Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 05/18] tracing: not necessary to undefine DEFINE_EVENT again Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 06/18] tracing: not necessary re-define DEFINE_EVENT_PRINT Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 07/18] tracing: define DEFINE_EVENT_PRINT not related to DEFINE_EVENT Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 08/18] tracing: not necessary to define DEFINE_EVENT_PRINT to be empty again Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 09/18] tracing: Move pipe reference to trace array instead of current_tracer Steven Rostedt
2020-07-31 19:33 ` dann frazier
2020-07-31 21:16 ` Steven Rostedt
2020-07-31 21:17 ` dann frazier
2020-07-02 21:58 ` [for-next][PATCH 10/18] ring-buffer: Have nested events still record running time stamp Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 11/18] ring-buffer: Incorporate absolute timestamp into add_timestamp logic Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 12/18] ring-buffer: Add rb_time_t 64 bit operations for speeding up 32 bit Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 13/18] ring-buffer: speed up buffer resets by avoiding synchronize_rcu for each CPU Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 14/18] ring-buffer: Mark the !tail (crossing a page) as unlikely Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 15/18] ring-buffer: Consolidate add_timestamp to remove some branches Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 16/18] ring-buffer: Move the add_timestamp into its own function Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 17/18] ring-buffer: Call trace_clock_local() directly for RETPOLINE kernels Steven Rostedt
2020-07-02 21:58 ` [for-next][PATCH 18/18] ring-buffer: Do not trigger a WARN if clock going backwards is detected Steven Rostedt
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200703081000.GT4800@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=akpm@linux-foundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=rostedt@goodmis.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).