From f9d4861fc32b995b1616775614459b8f266c803c Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Fri, 20 Jan 2012 12:01:13 +0100 Subject: [PATCH] ARM: 7294/1: vectors: use gate_vma for vectors user mapping The current user mapping for the vectors page is inserted as a `horrible hack vma' into each task via arch_setup_additional_pages. This causes problems with the MM subsystem and vm_normal_page, as described here: https://lkml.org/lkml/2012/1/14/55 Following the suggestion from Hugh in the above thread, this patch uses the gate_vma for the vectors user mapping, therefore consolidating the horrible hack VMAs into one. Acked-and-Tested-by: Nicolas Pitre Signed-off-by: Will Deacon Signed-off-by: Russell King --- arch/arm/include/asm/elf.h | 4 ---- arch/arm/include/asm/mmu_context.h | 29 +---------------------- arch/arm/include/asm/page.h | 2 ++ arch/arm/kernel/process.c | 38 ++++++++++++++++++++++-------- 4 files changed, 31 insertions(+), 42 deletions(-) diff --git a/arch/arm/include/asm/elf.h b/arch/arm/include/asm/elf.h index 0e9ce8d9686e..38050b1c4800 100644 --- a/arch/arm/include/asm/elf.h +++ b/arch/arm/include/asm/elf.h @@ -130,8 +130,4 @@ struct mm_struct; extern unsigned long arch_randomize_brk(struct mm_struct *mm); #define arch_randomize_brk arch_randomize_brk -extern int vectors_user_mapping(void); -#define arch_setup_additional_pages(bprm, uses_interp) vectors_user_mapping() -#define ARCH_HAS_SETUP_ADDITIONAL_PAGES - #endif diff --git a/arch/arm/include/asm/mmu_context.h b/arch/arm/include/asm/mmu_context.h index 71605d9f8e42..a0b3cac0547c 100644 --- a/arch/arm/include/asm/mmu_context.h +++ b/arch/arm/include/asm/mmu_context.h @@ -18,6 +18,7 @@ #include #include #include +#include void __check_kvm_seq(struct mm_struct *mm); @@ -133,32 +134,4 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next, #define deactivate_mm(tsk,mm) do { } while (0) #define activate_mm(prev,next) switch_mm(prev, next, NULL) -/* - * We are inserting a "fake" vma for the user-accessible vector page so - * gdb and friends can get to it through ptrace and /proc//mem. - * But we also want to remove it before the generic code gets to see it - * during process exit or the unmapping of it would cause total havoc. - * (the macro is used as remove_vma() is static to mm/mmap.c) - */ -#define arch_exit_mmap(mm) \ -do { \ - struct vm_area_struct *high_vma = find_vma(mm, 0xffff0000); \ - if (high_vma) { \ - BUG_ON(high_vma->vm_next); /* it should be last */ \ - if (high_vma->vm_prev) \ - high_vma->vm_prev->vm_next = NULL; \ - else \ - mm->mmap = NULL; \ - rb_erase(&high_vma->vm_rb, &mm->mm_rb); \ - mm->mmap_cache = NULL; \ - mm->map_count--; \ - remove_vma(high_vma); \ - } \ -} while (0) - -static inline void arch_dup_mmap(struct mm_struct *oldmm, - struct mm_struct *mm) -{ -} - #endif diff --git a/arch/arm/include/asm/page.h b/arch/arm/include/asm/page.h index 97b440c25c58..5838361c48b3 100644 --- a/arch/arm/include/asm/page.h +++ b/arch/arm/include/asm/page.h @@ -151,6 +151,8 @@ extern void __cpu_copy_user_highpage(struct page *to, struct page *from, #define clear_page(page) memset((void *)(page), 0, PAGE_SIZE) extern void copy_page(void *to, const void *from); +#define __HAVE_ARCH_GATE_AREA 1 + #ifdef CONFIG_ARM_LPAE #include #else diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index 971d65c253a9..e11b523db332 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -526,22 +526,40 @@ unsigned long arch_randomize_brk(struct mm_struct *mm) #ifdef CONFIG_MMU /* * The vectors page is always readable from user space for the - * atomic helpers and the signal restart code. Let's declare a mapping - * for it so it is visible through ptrace and /proc//mem. + * atomic helpers and the signal restart code. Insert it into the + * gate_vma so that it is visible through ptrace and /proc//mem. */ +static struct vm_area_struct gate_vma; -int vectors_user_mapping(void) +static int __init gate_vma_init(void) { - struct mm_struct *mm = current->mm; - return install_special_mapping(mm, 0xffff0000, PAGE_SIZE, - VM_READ | VM_EXEC | - VM_MAYREAD | VM_MAYEXEC | - VM_ALWAYSDUMP | VM_RESERVED, - NULL); + gate_vma.vm_start = 0xffff0000; + gate_vma.vm_end = 0xffff0000 + PAGE_SIZE; + gate_vma.vm_page_prot = PAGE_READONLY_EXEC; + gate_vma.vm_flags = VM_READ | VM_EXEC | + VM_MAYREAD | VM_MAYEXEC | + VM_ALWAYSDUMP; + return 0; +} +arch_initcall(gate_vma_init); + +struct vm_area_struct *get_gate_vma(struct mm_struct *mm) +{ + return &gate_vma; +} + +int in_gate_area(struct mm_struct *mm, unsigned long addr) +{ + return (addr >= gate_vma.vm_start) && (addr < gate_vma.vm_end); +} + +int in_gate_area_no_mm(unsigned long addr) +{ + return in_gate_area(NULL, addr); } const char *arch_vma_name(struct vm_area_struct *vma) { - return (vma->vm_start == 0xffff0000) ? "[vectors]" : NULL; + return (vma == &gate_vma) ? "[vectors]" : NULL; } #endif