From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Kees Cook <keescook@chromium.org>
Cc: linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
PaX Team <pageexec@freemail.hu>, Jann Horn <jannh@google.com>,
Eric Biggers <ebiggers3@gmail.com>,
Christoph Hellwig <hch@infradead.org>,
"axboe@kernel.dk" <axboe@kernel.dk>,
James Bottomley <James.Bottomley@hansenpartnership.com>,
Elena Reshetova <elena.reshetova@intel.com>,
Hans Liljestrand <ishkamiel@gmail.com>,
David Windsor <dwindsor@gmail.com>,
"x86@kernel.org" <x86@kernel.org>, Ingo Molnar <mingo@kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"David S. Miller" <davem@davemloft.net>,
Rik van Riel <riel@redhat.com>,
linux-arch <linux-arch@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>
Subject: Re: [PATCH v3 2/2] x86/refcount: Implement fast refcount overflow protection
Date: Mon, 8 May 2017 17:53:08 -0500 [thread overview]
Message-ID: <20170508225308.a6uznrhdm7pgyhcg@treble> (raw)
In-Reply-To: <1494271972-140319-3-git-send-email-keescook@chromium.org>
On Mon, May 08, 2017 at 12:32:52PM -0700, Kees Cook wrote:
> +#define REFCOUNT_EXCEPTION \
> + "movl $0x7fffffff, %[counter]\n\t" \
> + "int $"__stringify(X86_REFCOUNT_VECTOR)"\n" \
> + "0:\n\t" \
> + _ASM_EXTABLE(0b, 0b)
Despite the objtool warnings going away, this still uses the exception
table in a new way, which will confuse objtool. I need to do some more
thinking about the best way to fix it, either as a change to your patch
or a change to objtool.
> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
> index 532372c6cf15..0590f384f234 100644
> --- a/include/asm-generic/sections.h
> +++ b/include/asm-generic/sections.h
> @@ -20,6 +20,8 @@
> * may be out of this range on some architectures.
> * [_sinittext, _einittext]: contains .init.text.* sections
> * [__bss_start, __bss_stop]: contains BSS sections
> + * [__refcount_overflow/underflow_start, ..._end]: contains .text sections
> + * for refcount error handling.
> *
> * Following global variables are optional and may be unavailable on some
> * architectures and/or kernel configurations.
> @@ -39,6 +41,8 @@ extern char __per_cpu_load[], __per_cpu_start[], __per_cpu_end[];
> extern char __kprobes_text_start[], __kprobes_text_end[];
> extern char __entry_text_start[], __entry_text_end[];
> extern char __start_rodata[], __end_rodata[];
> +extern char __refcount_overflow_start[], __refcount_overflow_end[];
> +extern char __refcount_underflow_start[], __refcount_underflow_end[];
I think this part is no longer needed, since you got rid of the new
sections?
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index 3558f4eb1a86..2f2f34942689 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -446,9 +446,18 @@
> ALIGN_FUNCTION(); \
> *(.text.hot .text .text.fixup .text.unlikely) \
> *(.ref.text) \
> + REFCOUNT_TEXT \
> MEM_KEEP(init.text) \
> MEM_KEEP(exit.text) \
>
> +#define __REFCOUNT_TEXT(section) \
> + VMLINUX_SYMBOL(__##section##_start) = .; \
> + *(.text.##section) \
> + VMLINUX_SYMBOL(__##section##_end) = .;
> +
> +#define REFCOUNT_TEXT \
> + __REFCOUNT_TEXT(refcount_overflow) \
> + __REFCOUNT_TEXT(refcount_underflow)
Same here.
--
Josh
next prev parent reply other threads:[~2017-05-08 22:53 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-08 19:32 [PATCH v3 0/2] x86/refcount: Implement fast refcount overflow protection Kees Cook
2017-05-08 19:32 ` [PATCH v3 1/2] x86/asm: Add suffix macro for GEN_*_RMWcc() Kees Cook
2017-05-08 19:32 ` [PATCH v3 2/2] x86/refcount: Implement fast refcount overflow protection Kees Cook
2017-05-08 22:53 ` Josh Poimboeuf [this message]
2017-05-08 23:31 ` Kees Cook
2017-05-09 1:58 ` Josh Poimboeuf
2017-05-09 17:08 ` Josh Poimboeuf
2017-05-09 17:29 ` Kees Cook
2017-05-09 17:44 ` Josh Poimboeuf
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