From: Borislav Petkov <bp@alien8.de>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Garnier <thgarnie@chromium.org>,
kernel-hardening@lists.openwall.com, kristen@linux.intel.com,
keescook@chromium.org, Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v9 04/11] x86/entry/64: Adapt assembly for PIE support
Date: Tue, 6 Aug 2019 17:35:30 +0200 [thread overview]
Message-ID: <20190806153530.GC25897@zn.tnic> (raw)
In-Reply-To: <20190806135942.xnuovr4vbanbxneb@home.goodmis.org>
On Tue, Aug 06, 2019 at 09:59:42AM -0400, Steven Rostedt wrote:
> As Peter stated later in this thread, we only have the IRQ stack frame saved
> here, because we just took an NMI, and this is the logic to determine if it
> was a nested NMI or not (where we have to be *very* careful about touching the
> stack!)
>
> That said, the code modified here is to test the NMI nesting logic (only
> enabled with CONFIG_DEBUG_ENTRY), and what it is doing is re-enabling NMIs
> before calling the first NMI handler, to help trigger nested NMIs without the
> need of a break point or page fault (iret enables NMIs again).
>
> This code is in the path of the "first nmi" (we confirmed that this is not
> nested), which means that it should be safe to push onto the stack.
Thanks for the explanation!
> Yes, we need to save and restore whatever reg we used. The only comment I
> would make is to use %rdx instead of %rax as that has been our "scratch"
> register used before saving pt_regs. Just to be consistent.
Yap, makes sense.
Thx.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
next prev parent reply other threads:[~2019-08-06 15:35 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-30 19:12 [PATCH v9 00/11] x86: PIE support to extend KASLR randomization Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 01/11] x86/crypto: Adapt assembly for PIE support Thomas Garnier
2019-08-05 16:32 ` Borislav Petkov
2019-08-05 16:54 ` Kees Cook
2019-08-05 17:27 ` Borislav Petkov
2019-08-05 17:53 ` Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 02/11] x86: Add macro to get symbol address " Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 03/11] x86: relocate_kernel - Adapt assembly " Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 04/11] x86/entry/64: " Thomas Garnier
2019-08-05 17:28 ` Borislav Petkov
2019-08-05 17:50 ` Thomas Garnier
2019-08-06 5:08 ` Borislav Petkov
2019-08-06 8:30 ` Peter Zijlstra
2019-08-06 12:35 ` Borislav Petkov
2019-08-06 13:59 ` Steven Rostedt
2019-08-06 15:35 ` Borislav Petkov [this message]
2019-07-30 19:12 ` [PATCH v9 05/11] x86: pm-trace - " Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 06/11] x86/CPU: " Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 07/11] x86/acpi: " Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 08/11] x86/boot/64: " Thomas Garnier
2019-08-09 17:30 ` Borislav Petkov
2019-10-29 21:29 ` Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 09/11] x86/power/64: " Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 10/11] x86/paravirt: " Thomas Garnier
2019-07-31 12:53 ` Peter Zijlstra
2019-08-12 12:55 ` Borislav Petkov
2019-10-29 21:30 ` Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 11/11] x86/alternatives: " Thomas Garnier
2019-08-12 13:57 ` Borislav Petkov
2019-10-29 21:31 ` Thomas Garnier
2019-08-06 15:43 ` [PATCH v9 00/11] x86: PIE support to extend KASLR randomization Borislav Petkov
2019-08-06 15:50 ` Peter Zijlstra
2019-08-29 19:55 ` Thomas Garnier
2019-09-06 23:22 ` Thomas Garnier
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