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Re: [PATCH 4/5 v3] ftrace/x86_32: Clean up ftrace_regs_caller

From Linus Torvalds <torvalds@linux-foundation.org>
Newsgroups linux.kernel
Subject Re: [PATCH 4/5 v3] ftrace/x86_32: Clean up ftrace_regs_caller
Date 2017-03-16 19:30 +0100
Message-ID <tlIjV-2f6-53@gated-at.bofh.it> (permalink)
References <tlHnP-1ze-5@gated-at.bofh.it> <tlHnQ-1ze-15@gated-at.bofh.it> <tlHHc-1ID-17@gated-at.bofh.it> <tlI0y-25v-33@gated-at.bofh.it>
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On Thu, Mar 16, 2017 at 11:09 AM, Steven Rostedt <rostedt@goodmis.org> wrote:
> +
> +       /* Since we don't care about cs, move flags there to simplify return */
> +       movl    14*4(%esp), %eax
> +       movl    %eax, 13*4(%esp)
> +
> +       /* Move return ip back to its original location */
> +       movl    12*4(%esp), %eax
> +       movl    %eax, 14*4(%esp)

Could this perhaps be removed entirely?

The return code could instead do:

        ... restore all the normal registers ..

        # Now restore flags that is under the return address and our
fake __KERNEL_CS
        pushl 8(%esp)
        popfl

        # and then return, skipping __KERNEL_CS and %flasg
        ret $8

which is smaller and simpler than (again) playing games with stack entries.

                Linus

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Thread

[PATCH 4/5 v2] ftrace/x86_32: Clean up ftrace_regs_caller Steven Rostedt <rostedt@goodmis.org> - 2017-03-16 18:30 +0100
  Re: [PATCH 4/5 v2] ftrace/x86_32: Clean up ftrace_regs_caller Linus Torvalds <torvalds@linux-foundation.org> - 2017-03-16 18:50 +0100
    Re: [PATCH 4/5 v2] ftrace/x86_32: Clean up ftrace_regs_caller Steven Rostedt <rostedt@goodmis.org> - 2017-03-16 19:00 +0100
    [PATCH 4/5 v3] ftrace/x86_32: Clean up ftrace_regs_caller Steven Rostedt <rostedt@goodmis.org> - 2017-03-16 19:10 +0100
      Re: [PATCH 4/5 v3] ftrace/x86_32: Clean up ftrace_regs_caller Linus Torvalds <torvalds@linux-foundation.org> - 2017-03-16 19:30 +0100
        Re: [PATCH 4/5 v3] ftrace/x86_32: Clean up ftrace_regs_caller Linus Torvalds <torvalds@linux-foundation.org> - 2017-03-16 20:30 +0100
          Re: [PATCH 4/5 v3] ftrace/x86_32: Clean up ftrace_regs_caller Steven Rostedt <rostedt@goodmis.org> - 2017-03-16 20:50 +0100
        Re: [PATCH 4/5 v3] ftrace/x86_32: Clean up ftrace_regs_caller Steven Rostedt <rostedt@goodmis.org> - 2017-03-16 20:30 +0100
          Re: [PATCH 4/5 v3] ftrace/x86_32: Clean up ftrace_regs_caller Linus Torvalds <torvalds@linux-foundation.org> - 2017-03-16 20:40 +0100
            Re: [PATCH 4/5 v3] ftrace/x86_32: Clean up ftrace_regs_caller Steven Rostedt <rostedt@goodmis.org> - 2017-03-16 21:00 +0100
        Re: [PATCH 4/5 v3] ftrace/x86_32: Clean up ftrace_regs_caller Steven Rostedt <rostedt@goodmis.org> - 2017-03-16 20:30 +0100
        [PATCH 4/5 v3.1] ftrace/x86_32: Clean up ftrace_regs_caller Steven Rostedt <rostedt@goodmis.org> - 2017-03-16 21:20 +0100

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