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From: hpa@zytor.com
To: Thomas Garnier <thgarnie@chromium.org>,
	kernel-hardening@lists.openwall.com
Cc: kristen@linux.intel.com, Thomas Garnier <thgarnie@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
	Nadav Amit <namit@vmware.com>, Jann Horn <jannh@google.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v7 03/12] x86: Add macro to get symbol address for PIE support
Date: Mon, 20 May 2019 20:12:55 -0700	[thread overview]
Message-ID: <FF111368-9173-4AC2-9A79-E79A52B104DD@zytor.com> (raw)
In-Reply-To: <20190520231948.49693-4-thgarnie@chromium.org>

On May 20, 2019 4:19:28 PM PDT, Thomas Garnier <thgarnie@chromium.org> wrote:
>From: Thomas Garnier <thgarnie@google.com>
>
>Add a new _ASM_MOVABS macro to fetch a symbol address. It will be used
>to replace "_ASM_MOV $<symbol>, %dst" code construct that are not
>compatible with PIE.
>
>Signed-off-by: Thomas Garnier <thgarnie@google.com>
>---
> arch/x86/include/asm/asm.h | 1 +
> 1 file changed, 1 insertion(+)
>
>diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
>index 3ff577c0b102..3a686057e882 100644
>--- a/arch/x86/include/asm/asm.h
>+++ b/arch/x86/include/asm/asm.h
>@@ -30,6 +30,7 @@
> #define _ASM_ALIGN	__ASM_SEL(.balign 4, .balign 8)
> 
> #define _ASM_MOV	__ASM_SIZE(mov)
>+#define _ASM_MOVABS	__ASM_SEL(movl, movabsq)
> #define _ASM_INC	__ASM_SIZE(inc)
> #define _ASM_DEC	__ASM_SIZE(dec)
> #define _ASM_ADD	__ASM_SIZE(add)

This is just about *always* wrong on x86-86. We should be using leaq sym(%rip),%reg. If it isn't reachable by leaq, then it is a non-PIE symbol like percpu. You do have to keep those distinct!
-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.

  reply	other threads:[~2019-05-21  3:13 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-20 23:19 [PATCH v7 00/12] x86: PIE support to extend KASLR randomization Thomas Garnier
2019-05-20 23:19 ` [PATCH v7 01/12] x86/crypto: Adapt assembly for PIE support Thomas Garnier
2019-05-21  4:06   ` Eric Biggers
2019-05-22 20:47     ` Thomas Garnier
2019-05-22 20:55       ` Eric Biggers
2019-05-29 15:48         ` Thomas Garnier
2019-05-20 23:19 ` [PATCH v7 02/12] x86: Use symbol name in jump table " Thomas Garnier
2019-05-20 23:23   ` Thomas Garnier
2019-05-20 23:19 ` [PATCH v7 03/12] x86: Add macro to get symbol address " Thomas Garnier
2019-05-21  3:12   ` hpa [this message]
2019-05-22 15:57     ` Thomas Garnier
2019-05-20 23:19 ` [PATCH v7 04/12] x86: relocate_kernel - Adapt assembly " Thomas Garnier
2019-06-10 21:33   ` Kees Cook
2019-05-20 23:19 ` [PATCH v7 05/12] x86/entry/64: " Thomas Garnier
2019-06-10 21:34   ` Kees Cook
2019-05-20 23:19 ` [PATCH v7 06/12] x86: pm-trace - " Thomas Garnier
2019-06-10 21:34   ` Kees Cook
2019-05-20 23:19 ` [PATCH v7 07/12] x86/CPU: " Thomas Garnier
2019-05-20 23:19 ` [PATCH v7 08/12] x86/acpi: " Thomas Garnier
2019-06-10 23:52   ` Kees Cook
2019-05-20 23:19 ` [PATCH v7 09/12] x86/boot/64: " Thomas Garnier
2019-06-10 22:26   ` Kees Cook
2019-05-20 23:19 ` [PATCH v7 10/12] x86/power/64: " Thomas Garnier
2019-06-10 23:52   ` Kees Cook
2019-05-20 23:19 ` [PATCH v7 11/12] x86/paravirt: " Thomas Garnier
2019-05-27  5:47   ` Juergen Gross
2019-05-29 15:48     ` Thomas Garnier
2019-05-20 23:19 ` [PATCH v7 12/12] x86/alternatives: " Thomas Garnier
2019-06-10 21:32 ` [PATCH v7 00/12] x86: PIE support to extend KASLR randomization Kees Cook

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