From 63b2bc619565ef7078e7b12fafb82f51867f002b Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Thu, 21 Feb 2019 19:08:49 +0000 Subject: powerpc/mm/32s: Use BATs for STRICT_KERNEL_RWX Today, STRICT_KERNEL_RWX is based on the use of regular pages to map kernel pages. On Book3s 32, it has three consequences: - Using pages instead of BAT for mapping kernel linear memory severely impacts performance. - Exec protection is not effective because no-execute cannot be set at page level (except on 603 which doesn't have hash tables) - Write protection is not effective because PP bits do not provide RO mode for kernel-only pages (except on 603 which handles it in software via PAGE_DIRTY) On the 603+, we have: - Independent IBAT and DBAT allowing limitation of exec parts. - NX bit can be set in segment registers to forbit execution on memory mapped by pages. - RO mode on DBATs even for kernel-only blocks. On the 601, there is nothing much we can do other than warn the user about it, because: - BATs are common to instructions and data. - BAT do not provide RO mode for kernel-only blocks. - segment registers don't have the NX bit. In order to use IBAT for exec protection, this patch: - Aligns _etext to BAT block sizes (128kb) - Set NX bit in kernel segment register (Except on vmalloc area when CONFIG_MODULES is selected) - Maps kernel text with IBATs. In order to use DBAT for exec protection, this patch: - Aligns RW DATA to BAT block sizes (4M) - Maps kernel RO area with write prohibited DBATs - Maps remaining memory with remaining DBATs Here is what we get with this patch on a 832x when activating STRICT_KERNEL_RWX: Symbols: c0000000 T _stext c0680000 R __start_rodata c0680000 R _etext c0800000 T __init_begin c0800000 T _sinittext ~# cat /sys/kernel/debug/block_address_translation ---[ Instruction Block Address Translation ]--- 0: 0xc0000000-0xc03fffff 0x00000000 Kernel EXEC coherent 1: 0xc0400000-0xc05fffff 0x00400000 Kernel EXEC coherent 2: 0xc0600000-0xc067ffff 0x00600000 Kernel EXEC coherent 3: - 4: - 5: - 6: - 7: - ---[ Data Block Address Translation ]--- 0: 0xc0000000-0xc07fffff 0x00000000 Kernel RO coherent 1: 0xc0800000-0xc0ffffff 0x00800000 Kernel RW coherent 2: 0xc1000000-0xc1ffffff 0x01000000 Kernel RW coherent 3: 0xc2000000-0xc3ffffff 0x02000000 Kernel RW coherent 4: 0xc4000000-0xc7ffffff 0x04000000 Kernel RW coherent 5: 0xc8000000-0xcfffffff 0x08000000 Kernel RW coherent 6: 0xd0000000-0xdfffffff 0x10000000 Kernel RW coherent 7: - ~# cat /sys/kernel/debug/segment_registers ---[ User Segments ]--- 0x00000000-0x0fffffff Kern key 1 User key 1 VSID 0xa085d0 0x10000000-0x1fffffff Kern key 1 User key 1 VSID 0xa086e1 0x20000000-0x2fffffff Kern key 1 User key 1 VSID 0xa087f2 0x30000000-0x3fffffff Kern key 1 User key 1 VSID 0xa08903 0x40000000-0x4fffffff Kern key 1 User key 1 VSID 0xa08a14 0x50000000-0x5fffffff Kern key 1 User key 1 VSID 0xa08b25 0x60000000-0x6fffffff Kern key 1 User key 1 VSID 0xa08c36 0x70000000-0x7fffffff Kern key 1 User key 1 VSID 0xa08d47 0x80000000-0x8fffffff Kern key 1 User key 1 VSID 0xa08e58 0x90000000-0x9fffffff Kern key 1 User key 1 VSID 0xa08f69 0xa0000000-0xafffffff Kern key 1 User key 1 VSID 0xa0907a 0xb0000000-0xbfffffff Kern key 1 User key 1 VSID 0xa0918b ---[ Kernel Segments ]--- 0xc0000000-0xcfffffff Kern key 0 User key 1 No Exec VSID 0x000ccc 0xd0000000-0xdfffffff Kern key 0 User key 1 No Exec VSID 0x000ddd 0xe0000000-0xefffffff Kern key 0 User key 1 No Exec VSID 0x000eee 0xf0000000-0xffffffff Kern key 0 User key 1 No Exec VSID 0x000fff Aligning _etext to 128kb allows to map up to 32Mb text with 8 IBATs: 16Mb + 8Mb + 4Mb + 2Mb + 1Mb + 512kb + 256kb + 128kb (+ 128kb) = 32Mb (A 9th IBAT is unneeded as 32Mb would need only a single 32Mb block) Aligning data to 4M allows to map up to 512Mb data with 8 DBATs: 16Mb + 8Mb + 4Mb + 4Mb + 32Mb + 64Mb + 128Mb + 256Mb = 512Mb Because some processors only have 4 BATs and because some targets need DBATs for mapping other areas, the following patch will allow to modify _etext and data alignment. Signed-off-by: Christophe Leroy Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman --- arch/powerpc/mm/ppc_mmu_32.c | 87 +++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 81 insertions(+), 6 deletions(-) (limited to 'arch/powerpc/mm/ppc_mmu_32.c') diff --git a/arch/powerpc/mm/ppc_mmu_32.c b/arch/powerpc/mm/ppc_mmu_32.c index 7b011280d076..2d5b0d50fb31 100644 --- a/arch/powerpc/mm/ppc_mmu_32.c +++ b/arch/powerpc/mm/ppc_mmu_32.c @@ -32,6 +32,7 @@ #include #include #include +#include #include "mmu_decl.h" @@ -138,15 +139,10 @@ static void clearibat(int index) bat[0].batl = 0; } -unsigned long __init mmu_mapin_ram(unsigned long base, unsigned long top) +static unsigned long __init __mmu_mapin_ram(unsigned long base, unsigned long top) { int idx; - if (__map_without_bats) { - printk(KERN_DEBUG "RAM mapped without BATs\n"); - return base; - } - while ((idx = find_free_bat()) != -1 && base != top) { unsigned int size = block_size(base, top); @@ -159,6 +155,85 @@ unsigned long __init mmu_mapin_ram(unsigned long base, unsigned long top) return base; } +unsigned long __init mmu_mapin_ram(unsigned long base, unsigned long top) +{ + int done; + unsigned long border = (unsigned long)__init_begin - PAGE_OFFSET; + + if (__map_without_bats) { + pr_debug("RAM mapped without BATs\n"); + return base; + } + + if (!strict_kernel_rwx_enabled() || base >= border || top <= border) + return __mmu_mapin_ram(base, top); + + done = __mmu_mapin_ram(base, border); + if (done != border - base) + return done; + + return done + __mmu_mapin_ram(border, top); +} + +void mmu_mark_initmem_nx(void) +{ + int nb = mmu_has_feature(MMU_FTR_USE_HIGH_BATS) ? 8 : 4; + int i; + unsigned long base = (unsigned long)_stext - PAGE_OFFSET; + unsigned long top = (unsigned long)_etext - PAGE_OFFSET; + unsigned long size; + + if (cpu_has_feature(CPU_FTR_601)) + return; + + for (i = 0; i < nb - 1 && base < top && top - base > (128 << 10);) { + size = block_size(base, top); + setibat(i++, PAGE_OFFSET + base, base, size, PAGE_KERNEL_TEXT); + base += size; + } + if (base < top) { + 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; + } + setibat(i++, PAGE_OFFSET + base, base, size, PAGE_KERNEL_TEXT); + base += size; + } + for (; i < nb; i++) + clearibat(i); + + update_bats(); + + for (i = TASK_SIZE >> 28; i < 16; i++) { + /* Do not set NX on VM space for modules */ + if (IS_ENABLED(CONFIG_MODULES) && + (VMALLOC_START & 0xf0000000) == i << 28) + break; + mtsrin(mfsrin(i << 28) | 0x10000000, i << 28); + } +} + +void mmu_mark_rodata_ro(void) +{ + int nb = mmu_has_feature(MMU_FTR_USE_HIGH_BATS) ? 8 : 4; + int i; + + if (cpu_has_feature(CPU_FTR_601)) + return; + + for (i = 0; i < nb; i++) { + struct ppc_bat *bat = BATS[i]; + + if (bat_addrs[i].start < (unsigned long)__init_begin) + bat[1].batl = (bat[1].batl & ~BPP_RW) | BPP_RX; + } + + update_bats(); +} + /* * Set up one of the I/D BAT (block address translation) register pairs. * The parameters are not checked; in particular size must be a power -- cgit v1.2.3