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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 14/45] powerpc/32s: Don't warn when mapping RO data ROX.
Date: Tue, 19 May 2020 05:48:56 +0000 (UTC)
Message-ID: <6499f8eeb2a36330e5c9fc1cee9a79374875bd54.1589866984.git.christophe.leroy@csgroup.eu> (raw)
In-Reply-To: <cover.1589866984.git.christophe.leroy@csgroup.eu>

Mapping RO data as ROX is not an issue since that data
cannot be modified to introduce an exploit.

PPC64 accepts to have RO data mapped ROX, as a trade off
between kernel size and strictness of protection.

On PPC32, kernel size is even more critical as amount of
memory is usually small.

Depending on the number of available IBATs, the last IBATs
might overflow the end of text. Only warn if it crosses
the end of RO data.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/mm/book3s32/mmu.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/mm/book3s32/mmu.c b/arch/powerpc/mm/book3s32/mmu.c
index 39ba53ca5bb5..a9b2cbc74797 100644
--- a/arch/powerpc/mm/book3s32/mmu.c
+++ b/arch/powerpc/mm/book3s32/mmu.c
@@ -187,6 +187,7 @@ void mmu_mark_initmem_nx(void)
 	int i;
 	unsigned long base = (unsigned long)_stext - PAGE_OFFSET;
 	unsigned long top = (unsigned long)_etext - PAGE_OFFSET;
+	unsigned long border = (unsigned long)__init_begin - PAGE_OFFSET;
 	unsigned long size;
 
 	if (IS_ENABLED(CONFIG_PPC_BOOK3S_601))
@@ -201,9 +202,10 @@ void mmu_mark_initmem_nx(void)
 		size = block_size(base, top);
 		size = max(size, 128UL << 10);
 		if ((top - base) > size) {
-			if (strict_kernel_rwx_enabled())
-				pr_warn("Kernel _etext not properly aligned\n");
 			size <<= 1;
+			if (strict_kernel_rwx_enabled() && base + size > border)
+				pr_warn("Some RW data is getting mapped X. "
+					"Adjust CONFIG_DATA_SHIFT to avoid that.\n");
 		}
 		setibat(i++, PAGE_OFFSET + base, base, size, PAGE_KERNEL_TEXT);
 		base += size;
-- 
2.25.0


  parent reply index

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 ` Christophe Leroy [this message]
2020-05-25  5:40   ` [PATCH v4 14/45] powerpc/32s: Don't warn when mapping RO data ROX 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 ` [PATCH v4 36/45] powerpc/mm: Don't be too strict with _etext alignment on PPC32 Christophe Leroy
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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