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From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: [PATCH v4 36/45] powerpc/mm: Don't be too strict with _etext alignment on PPC32
Date: Tue, 19 May 2020 05:49:19 +0000 (UTC)	[thread overview]
Message-ID: <8c4a0d89d944eed984dd941e509614031a5ace2b.1589866984.git.christophe.leroy@csgroup.eu> (raw)
In-Reply-To: <cover.1589866984.git.christophe.leroy@csgroup.eu>

Similar to PPC64, accept to map RO data as ROX as a trade off between
between security and memory usage.

Having RO data executable is not a high risk as RO data can't be
modified to forge an exploit.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/Kconfig              | 26 --------------------------
 arch/powerpc/kernel/vmlinux.lds.S |  3 +--
 2 files changed, 1 insertion(+), 28 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 1d4ef4f27dec..d147d379b1b9 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -778,32 +778,6 @@ config THREAD_SHIFT
 	  Used to define the stack size. The default is almost always what you
 	  want. Only change this if you know what you are doing.
 
-config ETEXT_SHIFT_BOOL
-	bool "Set custom etext alignment" if STRICT_KERNEL_RWX && \
-					     (PPC_BOOK3S_32 || PPC_8xx)
-	depends on ADVANCED_OPTIONS
-	help
-	  This option allows you to set the kernel end of text alignment. When
-	  RAM is mapped by blocks, the alignment needs to fit the size and
-	  number of possible blocks. The default should be OK for most configs.
-
-	  Say N here unless you know what you are doing.
-
-config ETEXT_SHIFT
-	int "_etext shift" if ETEXT_SHIFT_BOOL
-	range 17 28 if STRICT_KERNEL_RWX && PPC_BOOK3S_32
-	range 19 23 if STRICT_KERNEL_RWX && PPC_8xx
-	default 17 if STRICT_KERNEL_RWX && PPC_BOOK3S_32
-	default 19 if STRICT_KERNEL_RWX && PPC_8xx
-	default PPC_PAGE_SHIFT
-	help
-	  On Book3S 32 (603+), IBATs are used to map kernel text.
-	  Smaller is the alignment, greater is the number of necessary IBATs.
-
-	  On 8xx, large pages (512kb or 8M) are used to map kernel linear
-	  memory. Aligning to 8M reduces TLB misses as only 8M pages are used
-	  in that case.
-
 config DATA_SHIFT_BOOL
 	bool "Set custom data alignment" if STRICT_KERNEL_RWX && \
 					    (PPC_BOOK3S_32 || PPC_8xx)
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 31a0f201fb6f..54f23205c2b9 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -15,7 +15,6 @@
 #include <asm/thread_info.h>
 
 #define STRICT_ALIGN_SIZE	(1 << CONFIG_DATA_SHIFT)
-#define ETEXT_ALIGN_SIZE	(1 << CONFIG_ETEXT_SHIFT)
 
 ENTRY(_stext)
 
@@ -116,7 +115,7 @@ SECTIONS
 
 	} :text
 
-	. = ALIGN(ETEXT_ALIGN_SIZE);
+	. = ALIGN(PAGE_SIZE);
 	_etext = .;
 	PROVIDE32 (etext = .);
 
-- 
2.25.0


  parent reply	other threads:[~2020-05-19  7:00 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-19  5:48 [PATCH v4 00/45] Use hugepages to map kernel mem on 8xx Christophe Leroy
2020-05-19  5:48 ` [PATCH v4 01/45] powerpc/kasan: Fix error detection on memory allocation Christophe Leroy
2020-05-19  5:48 ` [PATCH v4 02/45] powerpc/kasan: Fix issues by lowering KASAN_SHADOW_END Christophe Leroy
2020-05-19  5:48 ` [PATCH v4 03/45] powerpc/kasan: Fix shadow pages allocation failure Christophe Leroy
2020-05-19  5:48 ` [PATCH v4 04/45] powerpc/kasan: Remove unnecessary page table locking Christophe Leroy
2020-05-19  5:48 ` [PATCH v4 05/45] powerpc/kasan: Refactor update of early shadow mappings Christophe Leroy
2020-05-19  5:48 ` [PATCH v4 06/45] powerpc/kasan: Declare kasan_init_region() weak Christophe Leroy
2020-05-19  5:48 ` [PATCH v4 07/45] powerpc/ptdump: Limit size of flags text to 1/2 chars on PPC32 Christophe Leroy
2020-05-25  5:15   ` Michael Ellerman
2020-05-25 11:06     ` Christophe Leroy
2020-05-26 12:53       ` Michael Ellerman
2020-05-19  5:48 ` [PATCH v4 08/45] powerpc/ptdump: Reorder flags Christophe Leroy
2020-05-19  5:48 ` [PATCH v4 09/45] powerpc/ptdump: Add _PAGE_COHERENT flag Christophe Leroy
2020-05-19  5:48 ` [PATCH v4 10/45] powerpc/ptdump: Display size of BATs Christophe Leroy
2020-05-19  5:48 ` [PATCH v4 11/45] powerpc/ptdump: Standardise display of BAT flags Christophe Leroy
2020-05-19  5:48 ` [PATCH v4 12/45] powerpc/ptdump: Properly handle non standard page size Christophe Leroy
2020-05-19  5:48 ` [PATCH v4 13/45] powerpc/ptdump: Handle hugepd at PGD level Christophe Leroy
2020-05-19  5:48 ` [PATCH v4 14/45] powerpc/32s: Don't warn when mapping RO data ROX Christophe Leroy
2020-05-25  5:40   ` Michael Ellerman
2020-05-19  5:48 ` [PATCH v4 15/45] powerpc/mm: Allocate static page tables for fixmap Christophe Leroy
2020-05-19  5:48 ` [PATCH v4 16/45] powerpc/mm: Fix conditions to perform MMU specific management by blocks on PPC32 Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 17/45] powerpc/mm: PTE_ATOMIC_UPDATES is only for 40x Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 18/45] powerpc/mm: Refactor pte_update() on nohash/32 Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 19/45] powerpc/mm: Refactor pte_update() on book3s/32 Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 20/45] powerpc/mm: Standardise __ptep_test_and_clear_young() params between PPC32 and PPC64 Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 21/45] powerpc/mm: Standardise pte_update() prototype " Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 22/45] powerpc/mm: Create a dedicated pte_update() for 8xx Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 23/45] powerpc/mm: Reduce hugepd size for 8M hugepages on 8xx Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 24/45] powerpc/8xx: Drop CONFIG_8xx_COPYBACK option Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 25/45] powerpc/8xx: Prepare handlers for _PAGE_HUGE for 512k pages Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 26/45] powerpc/8xx: Manage 512k huge pages as standard pages Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 27/45] powerpc/8xx: Only 8M pages are hugepte pages now Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 28/45] powerpc/8xx: MM_SLICE is not needed anymore Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 29/45] powerpc/8xx: Move PPC_PIN_TLB options into 8xx Kconfig Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 30/45] powerpc/8xx: Add function to set pinned TLBs Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 31/45] powerpc/8xx: Don't set IMMR map anymore at boot Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 32/45] powerpc/8xx: Always pin TLBs at startup Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 33/45] powerpc/8xx: Drop special handling of Linear and IMMR mappings in I/D TLB handlers Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 34/45] powerpc/8xx: Remove now unused TLB miss functions Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 35/45] powerpc/8xx: Move DTLB perf handling closer Christophe Leroy
2020-05-19  5:49 ` Christophe Leroy [this message]
2020-05-19  5:49 ` [PATCH v4 37/45] powerpc/8xx: Refactor kernel address boundary comparison Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 38/45] powerpc/8xx: Add a function to early map kernel via huge pages Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 39/45] powerpc/8xx: Map IMMR with a huge page Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 40/45] powerpc/8xx: Map linear memory with huge pages Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 41/45] powerpc/8xx: Allow STRICT_KERNEL_RwX with pinned TLB Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 42/45] powerpc/8xx: Allow large TLBs with DEBUG_PAGEALLOC Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 43/45] powerpc/8xx: Implement dedicated kasan_init_region() Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 44/45] powerpc/32s: Allow mapping with BATs with DEBUG_PAGEALLOC Christophe Leroy
2020-05-19  5:49 ` [PATCH v4 45/45] powerpc/32s: Implement dedicated kasan_init_region() Christophe Leroy
2020-06-09  5:28 ` [PATCH v4 00/45] Use hugepages to map kernel mem on 8xx Michael Ellerman

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