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From: Thomas Garnier <thgarnie@chromium.org>
To: 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>,
	"H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Juergen Gross <jgross@suse.com>,
	Feng Tang <feng.tang@intel.com>,
	Maran Wilson <maran.wilson@oracle.com>,
	Jan Beulich <JBeulich@suse.com>,
	Andy Lutomirski <luto@kernel.org>,
	linux-kernel@vger.kernel.org
Subject: [PATCH v7 09/12] x86/boot/64: Adapt assembly for PIE support
Date: Mon, 20 May 2019 16:19:34 -0700	[thread overview]
Message-ID: <20190520231948.49693-10-thgarnie@chromium.org> (raw)
In-Reply-To: <20190520231948.49693-1-thgarnie@chromium.org>

From: Thomas Garnier <thgarnie@google.com>

Change the assembly code to use only relative references of symbols for the
kernel to be PIE compatible.

Early at boot, the kernel is mapped at a temporary address while preparing
the page table. To know the changes needed for the page table with KASLR,
the boot code calculate the difference between the expected address of the
kernel and the one chosen by KASLR. It does not work with PIE because all
symbols in code are relatives. Instead of getting the future relocated
virtual address, you will get the current temporary mapping.
Instructions were changed to have absolute 64-bit references.

Position Independent Executable (PIE) support will allow to extend the
KASLR randomization range below 0xffffffff80000000.

Signed-off-by: Thomas Garnier <thgarnie@google.com>
---
 arch/x86/kernel/head_64.S | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index bcd206c8ac90..64a4f0a22b20 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -90,8 +90,10 @@ startup_64:
 	popq	%rsi
 
 	/* Form the CR3 value being sure to include the CR3 modifier */
-	addq	$(early_top_pgt - __START_KERNEL_map), %rax
+	movabs  $(early_top_pgt - __START_KERNEL_map), %rcx
+	addq    %rcx, %rax
 	jmp 1f
+
 ENTRY(secondary_startup_64)
 	UNWIND_HINT_EMPTY
 	/*
@@ -120,7 +122,8 @@ ENTRY(secondary_startup_64)
 	popq	%rsi
 
 	/* Form the CR3 value being sure to include the CR3 modifier */
-	addq	$(init_top_pgt - __START_KERNEL_map), %rax
+	movabs	$(init_top_pgt - __START_KERNEL_map), %rcx
+	addq    %rcx, %rax
 1:
 
 	/* Enable PAE mode, PGE and LA57 */
@@ -138,7 +141,7 @@ ENTRY(secondary_startup_64)
 	movq	%rax, %cr3
 
 	/* Ensure I am executing from virtual addresses */
-	movq	$1f, %rax
+	movabs  $1f, %rax
 	ANNOTATE_RETPOLINE_SAFE
 	jmp	*%rax
 1:
@@ -235,11 +238,12 @@ ENTRY(secondary_startup_64)
 	 *	REX.W + FF /5 JMP m16:64 Jump far, absolute indirect,
 	 *		address given in m16:64.
 	 */
-	pushq	$.Lafter_lret	# put return address on stack for unwinder
+	movabs  $.Lafter_lret, %rax
+	pushq	%rax		# put return address on stack for unwinder
 	xorl	%ebp, %ebp	# clear frame pointer
-	movq	initial_code(%rip), %rax
+	leaq	initial_code(%rip), %rax
 	pushq	$__KERNEL_CS	# set correct cs
-	pushq	%rax		# target address in negative space
+	pushq	(%rax)		# target address in negative space
 	lretq
 .Lafter_lret:
 END(secondary_startup_64)
-- 
2.21.0.1020.gf2820cf01a-goog


  parent reply	other threads:[~2019-05-20 23:20 UTC|newest]

Thread overview: 34+ 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 ` 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
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 ` Thomas Garnier [this message]
2019-06-10 22:26   ` [PATCH v7 09/12] x86/boot/64: " 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
2019-05-20 23:19   ` Thomas Garnier
2019-05-27  5:47   ` Juergen Gross
2019-05-27  5:47   ` Juergen Gross
2019-05-29 15:48     ` Thomas Garnier
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
2019-06-10 21:32 ` Kees Cook

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