From 03dfee6d5f824d14e3ecb742518740de69e603cc Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Wed, 12 Apr 2017 14:56:36 +1000 Subject: [PATCH] powerpc/mm: Fix swapper_pg_dir size on 64-bit hash w/64K pages Recently in commit f6eedbba7a26 ("powerpc/mm/hash: Increase VA range to 128TB"), we increased H_PGD_INDEX_SIZE to 15 when we're building with 64K pages. This makes it larger than RADIX_PGD_INDEX_SIZE (13), which means the logic to calculate MAX_PGD_INDEX_SIZE in book3s/64/pgtable.h is wrong. The end result is that the PGD (Page Global Directory, ie top level page table) of the kernel (aka. swapper_pg_dir), is too small. This generally doesn't lead to a crash, as we don't use the full range in normal operation. However if we try to dump the kernel pagetables we can trigger a crash because we walk off the end of the pgd into other memory and eventually try to dereference something bogus: $ cat /sys/kernel/debug/kernel_pagetables Unable to handle kernel paging request for data at address 0xe8fece0000000000 Faulting instruction address: 0xc000000000072314 cpu 0xc: Vector: 380 (Data SLB Access) at [c0000000daa13890] pc: c000000000072314: ptdump_show+0x164/0x430 lr: c000000000072550: ptdump_show+0x3a0/0x430 dar: e802cf0000000000 seq_read+0xf8/0x560 full_proxy_read+0x84/0xc0 __vfs_read+0x6c/0x1d0 vfs_read+0xbc/0x1b0 SyS_read+0x6c/0x110 system_call+0x38/0xfc The root cause is that MAX_PGD_INDEX_SIZE isn't actually computed to be the max of H_PGD_INDEX_SIZE or RADIX_PGD_INDEX_SIZE. To fix that move the calculation into asm-offsets.c where we can do it easily using max(). Fixes: f6eedbba7a26 ("powerpc/mm/hash: Increase VA range to 128TB") Signed-off-by: Michael Ellerman --- arch/powerpc/include/asm/book3s/64/pgtable.h | 4 ---- arch/powerpc/kernel/asm-offsets.c | 4 ++-- 2 files changed, 2 insertions(+), 6 deletions(-) diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h index fb72ff6b98e6..fb8380a2d8d5 100644 --- a/arch/powerpc/include/asm/book3s/64/pgtable.h +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h @@ -232,10 +232,6 @@ extern unsigned long __pte_frag_nr; extern unsigned long __pte_frag_size_shift; #define PTE_FRAG_SIZE_SHIFT __pte_frag_size_shift #define PTE_FRAG_SIZE (1UL << PTE_FRAG_SIZE_SHIFT) -/* - * Pgtable size used by swapper, init in asm code - */ -#define MAX_PGD_TABLE_SIZE (sizeof(pgd_t) << RADIX_PGD_INDEX_SIZE) #define PTRS_PER_PTE (1 << PTE_INDEX_SIZE) #define PTRS_PER_PMD (1 << PMD_INDEX_SIZE) diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c index e7c8229a8812..8e1163426ccb 100644 --- a/arch/powerpc/kernel/asm-offsets.c +++ b/arch/powerpc/kernel/asm-offsets.c @@ -400,8 +400,8 @@ int main(void) DEFINE(BUG_ENTRY_SIZE, sizeof(struct bug_entry)); #endif -#ifdef MAX_PGD_TABLE_SIZE - DEFINE(PGD_TABLE_SIZE, MAX_PGD_TABLE_SIZE); +#ifdef CONFIG_PPC_BOOK3S_64 + DEFINE(PGD_TABLE_SIZE, (sizeof(pgd_t) << max(RADIX_PGD_INDEX_SIZE, H_PGD_INDEX_SIZE))); #else DEFINE(PGD_TABLE_SIZE, PGD_TABLE_SIZE); #endif -- 2.20.1