| Message ID | 20131024071258.GB16735@n2100.arm.linux.org.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi, Thanks for starting this work! Russel said: > -#define MT_MEMORY 9 > [...] > + MT_MEMORY, > + MT_MEMORY_NX, Instead of these names, let's more fully describe the protections. "NX" doesn't say anything about RO vs RW. Instead, how about: MT_MEMORY_RWX (to replace MT_MEMORY) MT_MEMORY_RW (as the new "NX" in use for this patch) for the first change? Then as we move forward, we can add: MT_MEMORY_R At which point we'll have the three states. -Kees
On Thu, Oct 24, 2013 at 01:45:02AM -0700, Kees Cook wrote: > Hi, > > Thanks for starting this work! > > Russel said: > > -#define MT_MEMORY 9 > > [...] > > + MT_MEMORY, > > + MT_MEMORY_NX, > > Instead of these names, let's more fully describe the protections. "NX" > doesn't say anything about RO vs RW. Instead, how about: > > MT_MEMORY_RWX (to replace MT_MEMORY) > MT_MEMORY_RW (as the new "NX" in use for this patch) > > for the first change? Then as we move forward, we can add: > > MT_MEMORY_R > > At which point we'll have the three states. Yes, we can. We have a few others which should be changed in the same way.
On Thu, 24 Oct 2013, Russell King - ARM Linux wrote: > This patch has similar functionality to Laura's patch set earlier this > month, except I've just done the basic change - we don't increase the > size of the kernel for this, so there should be no kernel size related > problems with this. We mark sections which do not overlap any kernel > text as non-executable. > > 8<==== > From: Russell King <rmk+kernel@arm.linux.org.uk> > ARM: Implement basic NX support for kernel lowmem mappings > > Add basic NX support for kernel lowmem mappings. We mark any section > which does not overlap kernel text as non-executable, preventing it > from being used to write code and then execute directly from there. > > This does not change the alignment of the sections, so the kernel > image doesn't grow significantly via this change, so we can do this > without needing a config option. > > Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> [...] > @@ -1294,6 +1309,8 @@ static void __init kmap_init(void) > static void __init map_lowmem(void) > { > struct memblock_region *reg; > + unsigned long kernel_x_start = round_down(__pa(_stext), SECTION_SIZE); > + unsigned long kernel_x_end = round_up(__pa(__init_end), SECTION_SIZE); Maybe a worthwhile config option could allow for the above to be rounded to PAGE_SIZE instead. That would require a second level page table for the kernel text edges with increased TLB pressure but also with tighter protection. That would also allow removing executability of __init memory after it is discarded. > /* Map all the lowmem memory banks. */ > for_each_memblock(memory, reg) { > @@ -1306,12 +1323,40 @@ static void __init map_lowmem(void) > if (start >= end) > break; > > - map.pfn = __phys_to_pfn(start); > - map.virtual = __phys_to_virt(start); > - map.length = end - start; > - map.type = MT_MEMORY; > + if (end < kernel_x_start || start >= kernel_x_end) { Isn't it supposed to be "end <= kernel_x_start" ? > + map.pfn = __phys_to_pfn(start); > + map.virtual = __phys_to_virt(start); > + map.length = end - start; > + map.type = MT_MEMORY; Isn't it supposed to be MT_MEMORY_NX here? > - create_mapping(&map); > + create_mapping(&map); > + } else { > + /* This better cover the entire kernel */ > + if (start < kernel_x_start) { > + map.pfn = __phys_to_pfn(start); > + map.virtual = __phys_to_virt(start); > + map.length = kernel_x_start - start; > + map.type = MT_MEMORY_NX; > + > + create_mapping(&map); > + } > + > + map.pfn = __phys_to_pfn(kernel_x_start); > + map.virtual = __phys_to_virt(kernel_x_start); > + map.length = kernel_x_end - kernel_x_start; > + map.type = MT_MEMORY; > + > + create_mapping(&map); > + > + if (kernel_x_end < end) { > + map.pfn = __phys_to_pfn(kernel_x_end); > + map.virtual = __phys_to_virt(kernel_x_end); > + map.length = end - kernel_x_end; > + map.type = MT_MEMORY_NX; > + > + create_mapping(&map); > + } > + } > } > } > > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
diff --git a/arch/arm/include/asm/mach/map.h b/arch/arm/include/asm/mach/map.h index 2fe141f..d43f100 100644 --- a/arch/arm/include/asm/mach/map.h +++ b/arch/arm/include/asm/mach/map.h @@ -22,18 +22,21 @@ struct map_desc { }; /* types 0-3 are defined in asm/io.h */ -#define MT_UNCACHED 4 -#define MT_CACHECLEAN 5 -#define MT_MINICLEAN 6 -#define MT_LOW_VECTORS 7 -#define MT_HIGH_VECTORS 8 -#define MT_MEMORY 9 -#define MT_ROM 10 -#define MT_MEMORY_NONCACHED 11 -#define MT_MEMORY_DTCM 12 -#define MT_MEMORY_ITCM 13 -#define MT_MEMORY_SO 14 -#define MT_MEMORY_DMA_READY 15 +enum { + MT_UNCACHED = 4, + MT_CACHECLEAN, + MT_MINICLEAN, + MT_LOW_VECTORS, + MT_HIGH_VECTORS, + MT_MEMORY, + MT_MEMORY_NX, + MT_ROM, + MT_MEMORY_NONCACHED, + MT_MEMORY_DTCM, + MT_MEMORY_ITCM, + MT_MEMORY_SO, + MT_MEMORY_DMA_READY, +}; #ifdef CONFIG_MMU extern void iotable_init(struct map_desc *, int); diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c index 53cdbd3..e8f0f94 100644 --- a/arch/arm/mm/mmu.c +++ b/arch/arm/mm/mmu.c @@ -22,6 +22,7 @@ #include <asm/cputype.h> #include <asm/sections.h> #include <asm/cachetype.h> +#include <asm/sections.h> #include <asm/setup.h> #include <asm/smp_plat.h> #include <asm/tlb.h> @@ -291,6 +292,13 @@ static struct mem_type mem_types[] = { .prot_sect = PMD_TYPE_SECT | PMD_SECT_AP_WRITE, .domain = DOMAIN_KERNEL, }, + [MT_MEMORY_NX] = { + .prot_pte = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY | + L_PTE_XN, + .prot_l1 = PMD_TYPE_TABLE, + .prot_sect = PMD_TYPE_SECT | PMD_SECT_AP_WRITE, + .domain = DOMAIN_KERNEL, + }, [MT_ROM] = { .prot_sect = PMD_TYPE_SECT, .domain = DOMAIN_KERNEL, @@ -408,6 +416,9 @@ static void __init build_mem_type_table(void) mem_types[MT_DEVICE_NONSHARED].prot_sect |= PMD_SECT_XN; mem_types[MT_DEVICE_CACHED].prot_sect |= PMD_SECT_XN; mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_XN; + + /* Also setup NX memory mapping */ + mem_types[MT_MEMORY_NX].prot_sect |= PMD_SECT_XN; } if (cpu_arch >= CPU_ARCH_ARMv7 && (cr & CR_TRE)) { /* @@ -487,6 +498,8 @@ static void __init build_mem_type_table(void) mem_types[MT_DEVICE_CACHED].prot_pte |= L_PTE_SHARED; mem_types[MT_MEMORY].prot_sect |= PMD_SECT_S; mem_types[MT_MEMORY].prot_pte |= L_PTE_SHARED; + mem_types[MT_MEMORY_NX].prot_sect |= PMD_SECT_S; + mem_types[MT_MEMORY_NX].prot_pte |= L_PTE_SHARED; mem_types[MT_MEMORY_DMA_READY].prot_pte |= L_PTE_SHARED; mem_types[MT_MEMORY_NONCACHED].prot_sect |= PMD_SECT_S; mem_types[MT_MEMORY_NONCACHED].prot_pte |= L_PTE_SHARED; @@ -543,6 +556,8 @@ static void __init build_mem_type_table(void) mem_types[MT_HIGH_VECTORS].prot_l1 |= ecc_mask; mem_types[MT_MEMORY].prot_sect |= ecc_mask | cp->pmd; mem_types[MT_MEMORY].prot_pte |= kern_pgprot; + mem_types[MT_MEMORY_NX].prot_sect |= ecc_mask | cp->pmd; + mem_types[MT_MEMORY_NX].prot_pte |= kern_pgprot; mem_types[MT_MEMORY_DMA_READY].prot_pte |= kern_pgprot; mem_types[MT_MEMORY_NONCACHED].prot_sect |= ecc_mask; mem_types[MT_ROM].prot_sect |= cp->pmd; @@ -1294,6 +1309,8 @@ static void __init kmap_init(void) static void __init map_lowmem(void) { struct memblock_region *reg; + unsigned long kernel_x_start = round_down(__pa(_stext), SECTION_SIZE); + unsigned long kernel_x_end = round_up(__pa(__init_end), SECTION_SIZE); /* Map all the lowmem memory banks. */ for_each_memblock(memory, reg) { @@ -1306,12 +1323,40 @@ static void __init map_lowmem(void) if (start >= end) break; - map.pfn = __phys_to_pfn(start); - map.virtual = __phys_to_virt(start); - map.length = end - start; - map.type = MT_MEMORY; + if (end < kernel_x_start || start >= kernel_x_end) { + map.pfn = __phys_to_pfn(start); + map.virtual = __phys_to_virt(start); + map.length = end - start; + map.type = MT_MEMORY; - create_mapping(&map); + create_mapping(&map); + } else { + /* This better cover the entire kernel */ + if (start < kernel_x_start) { + map.pfn = __phys_to_pfn(start); + map.virtual = __phys_to_virt(start); + map.length = kernel_x_start - start; + map.type = MT_MEMORY_NX; + + create_mapping(&map); + } + + map.pfn = __phys_to_pfn(kernel_x_start); + map.virtual = __phys_to_virt(kernel_x_start); + map.length = kernel_x_end - kernel_x_start; + map.type = MT_MEMORY; + + create_mapping(&map); + + if (kernel_x_end < end) { + map.pfn = __phys_to_pfn(kernel_x_end); + map.virtual = __phys_to_virt(kernel_x_end); + map.length = end - kernel_x_end; + map.type = MT_MEMORY_NX; + + create_mapping(&map); + } + } } }