[PATCH 1/1] Fixup write permission of TLB on powerpc e500 core
From: Shan Hai <hidden>
Date: 2011-07-15 08:06:00
Also in:
lkml
Subsystem:
linux for powerpc (32-bit and 64-bit), mmu gather and tlb invalidation, the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Will Deacon, "Aneesh Kumar K.V", Andrew Morton, Nick Piggin, Peter Zijlstra, Linus Torvalds
The kernel has no write permission on COW pages by default on e500 core, this will cause endless loop in futex_lock_pi, because futex code assumes the kernel has write permission on COW pages. Grant write permission to the kernel on COW pages when access violation page fault occurs. Signed-off-by: Shan Hai <redacted> --- arch/powerpc/include/asm/futex.h | 11 ++++++++++- arch/powerpc/include/asm/tlb.h | 25 +++++++++++++++++++++++++ 2 files changed, 35 insertions(+), 1 deletions(-)
diff --git a/arch/powerpc/include/asm/futex.h b/arch/powerpc/include/asm/futex.h
index c94e4a3..54c3e74 100644
--- a/arch/powerpc/include/asm/futex.h
+++ b/arch/powerpc/include/asm/futex.h@@ -8,6 +8,7 @@ #include <asm/errno.h> #include <asm/synch.h> #include <asm/asm-compat.h> +#include <asm/tlb.h> #define __futex_atomic_op(insn, ret, oldval, uaddr, oparg) \ __asm__ __volatile ( \
@@ -113,7 +114,15 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, : "cc", "memory"); *uval = prev; - return ret; + + /* Futex assumes the kernel has permission to write to + * COW pages, grant the kernel write permission on COW + * pages because it has none by default. + */ + if (ret == -EFAULT) + __tlb_fixup_write_permission(current->mm, (unsigned long)uaddr); + + return ret; } #endif /* __KERNEL__ */
diff --git a/arch/powerpc/include/asm/tlb.h b/arch/powerpc/include/asm/tlb.h
index e2b428b..3863c6a 100644
--- a/arch/powerpc/include/asm/tlb.h
+++ b/arch/powerpc/include/asm/tlb.h@@ -45,5 +45,30 @@ static inline void __tlb_remove_tlb_entry(struct mmu_gather *tlb, pte_t *ptep, #endif } +/* Grant write permission to the kernel on a page. */ +static inline void __tlb_fixup_write_permission(struct mm_struct *mm, + unsigned long address) +{ +#if defined(CONFIG_FSL_BOOKE) + /* Grant write permission to the kernel on a page by setting TLB.SW + * bit, the bit setting operation is tricky here, calling + * handle_mm_fault with FAULT_FLAG_WRITE causes _PAGE_DIRTY bit of + * the pte to be set, the _PAGE_DIRTY of the pte is translated into + * TLB.SW on Powerpc e500 core. + */ + + struct vm_area_struct *vma; + + vma = find_vma(mm, address); + if (likely(vma)) { + /* only fixup present page */ + if (follow_page(vma, address, FOLL_WRITE)) { + handle_mm_fault(mm, vma, address, FAULT_FLAG_WRITE); + flush_tlb_page(vma, address); + } + } +#endif +} + #endif /* __KERNEL__ */ #endif /* __ASM_POWERPC_TLB_H */
--
1.7.1