From mboxrd@z Thu Jan 1 00:00:00 1970 From: lauraa@codeaurora.org (Laura Abbott) Date: Tue, 8 Oct 2013 18:31:31 -0700 Subject: [RFC PATCH 4/5] arm: mm: restrict kernel memory permissions if CONFIG_STRICT_MEMORY_RWX set In-Reply-To: <1381282292-25251-1-git-send-email-lauraa@codeaurora.org> References: <1381282292-25251-1-git-send-email-lauraa@codeaurora.org> Message-ID: <1381282292-25251-5-git-send-email-lauraa@codeaurora.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org If CONFIG_STRICT_MEMORY_RWX is set, make kernel text RX, kernel data/stack RW and rodata RO so that writing on kernel text, executing kernel data or stack, or writing on or executing read-only data is prohibited. Signed-off-by: Larry Bassel Signed-off-by: Laura Abbott --- arch/arm/mm/mmu.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 files changed, 56 insertions(+), 1 deletions(-) diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c index d846334..91db2a0 100644 --- a/arch/arm/mm/mmu.c +++ b/arch/arm/mm/mmu.c @@ -1311,6 +1311,60 @@ static void __init kmap_init(void) #endif } +struct custom_map { + unsigned long start; + unsigned long end; + unsigned int type; +}; + +struct custom_map __initdata custom_maps[] = { + { + .start = _stext, + .end = __start_rodata, + .type = MT_MEMORY_RX, + }, + { + .start = __start_rodata, + .end = __init_begin, + .type = MT_MEMORY_R + }, + { + .start = __init_begin, + .end = __arch_info_begin, + .type = MT_MEMORY_RX, + } +}; + +static void __init map_custom_regions(void) +{ +#ifdef CONFIG_STRICT_MEMORY_RWX + int i; + + for (i = 0; i < ARRAY_SIZE(custom_maps); i++) { + struct map_desc map; + unsigned long addr; + + if (!IS_ALIGNED(custom_maps[i].start, PMD_SIZE) || + !IS_ALIGNED(custom_maps[i].end, PMD_SIZE)) { + pr_err("BUG: section %x-%x not aligned to %x\n", + custom_maps[i].start, custom_maps[i].end, + PMD_SIZE); + continue; + } + + for (addr = custom_maps[i].start; + addr < custom_maps[i].end; addr += PMD_SIZE) + pmd_clear(pmd_off_k(addr)); + + map.virtual = custom_maps[i].start; + map.pfn = __phys_to_pfn(__virt_to_phys(custom_maps[i].start)); + map.length = custom_maps[i].end - custom_maps[i].start; + map.type = custom_maps[i].type; + create_mapping(&map); + } +#endif +} + static void __init map_lowmem(void) { struct memblock_region *reg; @@ -1329,10 +1383,11 @@ static void __init map_lowmem(void) map.pfn = __phys_to_pfn(start); map.virtual = __phys_to_virt(start); map.length = end - start; - map.type = MT_MEMORY; + map.type = MT_MEMORY_RW; create_mapping(&map); } + map_custom_regions(); } /* -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation