Messages in this thread | | | From | Linus Torvalds <> | Date | Mon, 24 Oct 2022 11:19:31 -0700 | Subject | Re: [PATCH] x86/mm: Do not verify W^X at boot up |
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On Mon, Oct 24, 2022 at 8:45 AM Steven Rostedt <rostedt@goodmis.org> wrote: > > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > Adding on the kernel command line "ftrace=function" triggered: > > CPA detected W^X violation: 8000000000000063 -> 0000000000000063 range:
Hmm.
The cause of this actually seems to be this
if (likely(system_state != SYSTEM_BOOTING)) set_memory_ro((unsigned long)trampoline, npages); set_memory_x((unsigned long)trampoline, npages); return (unsigned long)trampoline;
in create_trampoline().
And that in turn is because of commit 59566b0b622e ("x86/ftrace: Have ftrace trampolines turn read-only at the end of system boot up"), which in turn is because of
if (unlikely(system_state == SYSTEM_BOOTING)) { text_poke_early(addr, opcode, len); return; }
in text_poke_bp(). And that, in turn, is because PeterZ ended up special-casing this all in commit 768ae4406a5c ("x86/ftrace: Use text_poke()")
Maybe we should just strive to get rid of all these SYSTEM_BOOTING special cases, instead of adding yet another a new one.
There's presumably "it slows down boot" reason to avoid the full text_poke_bp() dance, but do we really care for the "ftrace=function" case?
Linus
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