From 83086978c63afd7c73e1c173c84aeab184c1e916 Mon Sep 17 00:00:00 2001 From: HATAYAMA Daisuke Date: Wed, 3 Jul 2013 15:02:23 -0700 Subject: [PATCH] vmcore: support mmap() on /proc/vmcore This patch introduces mmap_vmcore(). Don't permit writable nor executable mapping even with mprotect() because this mmap() is aimed at reading crash dump memory. Non-writable mapping is also requirement of remap_pfn_range() when mapping linear pages on non-consecutive physical pages; see is_cow_mapping(). Set VM_MIXEDMAP flag to remap memory by remap_pfn_range and by remap_vmalloc_range_pertial at the same time for a single vma. do_munmap() can correctly clean partially remapped vma with two functions in abnormal case. See zap_pte_range(), vm_normal_page() and their comments for details. On x86-32 PAE kernels, mmap() supports at most 16TB memory only. This limitation comes from the fact that the third argument of remap_pfn_range(), pfn, is of 32-bit length on x86-32: unsigned long. [akpm@linux-foundation.org: use min(), switch to conventional error-unwinding approach] Signed-off-by: HATAYAMA Daisuke Acked-by: Vivek Goyal Cc: KOSAKI Motohiro Cc: Atsushi Kumagai Cc: Lisa Mitchell Cc: Zhang Yanfei Tested-by: Maxim Uvarov Cc: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/vmcore.c | 136 ++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 116 insertions(+), 20 deletions(-) diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c index 8ec648368985..28503172f2e4 100644 --- a/fs/proc/vmcore.c +++ b/fs/proc/vmcore.c @@ -20,6 +20,7 @@ #include #include #include +#include #include #include #include "internal.h" @@ -194,9 +195,122 @@ static ssize_t read_vmcore(struct file *file, char __user *buffer, return acc; } +/** + * alloc_elfnotes_buf - allocate buffer for ELF note segment in + * vmalloc memory + * + * @notes_sz: size of buffer + * + * If CONFIG_MMU is defined, use vmalloc_user() to allow users to mmap + * the buffer to user-space by means of remap_vmalloc_range(). + * + * If CONFIG_MMU is not defined, use vzalloc() since mmap_vmcore() is + * disabled and there's no need to allow users to mmap the buffer. + */ +static inline char *alloc_elfnotes_buf(size_t notes_sz) +{ +#ifdef CONFIG_MMU + return vmalloc_user(notes_sz); +#else + return vzalloc(notes_sz); +#endif +} + +/* + * Disable mmap_vmcore() if CONFIG_MMU is not defined. MMU is + * essential for mmap_vmcore() in order to map physically + * non-contiguous objects (ELF header, ELF note segment and memory + * regions in the 1st kernel pointed to by PT_LOAD entries) into + * virtually contiguous user-space in ELF layout. + */ +#ifdef CONFIG_MMU +static int mmap_vmcore(struct file *file, struct vm_area_struct *vma) +{ + size_t size = vma->vm_end - vma->vm_start; + u64 start, end, len, tsz; + struct vmcore *m; + + start = (u64)vma->vm_pgoff << PAGE_SHIFT; + end = start + size; + + if (size > vmcore_size || end > vmcore_size) + return -EINVAL; + + if (vma->vm_flags & (VM_WRITE | VM_EXEC)) + return -EPERM; + + vma->vm_flags &= ~(VM_MAYWRITE | VM_MAYEXEC); + vma->vm_flags |= VM_MIXEDMAP; + + len = 0; + + if (start < elfcorebuf_sz) { + u64 pfn; + + tsz = min(elfcorebuf_sz - (size_t)start, size); + pfn = __pa(elfcorebuf + start) >> PAGE_SHIFT; + if (remap_pfn_range(vma, vma->vm_start, pfn, tsz, + vma->vm_page_prot)) + return -EAGAIN; + size -= tsz; + start += tsz; + len += tsz; + + if (size == 0) + return 0; + } + + if (start < elfcorebuf_sz + elfnotes_sz) { + void *kaddr; + + tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)start, size); + kaddr = elfnotes_buf + start - elfcorebuf_sz; + if (remap_vmalloc_range_partial(vma, vma->vm_start + len, + kaddr, tsz)) + goto fail; + size -= tsz; + start += tsz; + len += tsz; + + if (size == 0) + return 0; + } + + list_for_each_entry(m, &vmcore_list, list) { + if (start < m->offset + m->size) { + u64 paddr = 0; + + tsz = min_t(size_t, m->offset + m->size - start, size); + paddr = m->paddr + start - m->offset; + if (remap_pfn_range(vma, vma->vm_start + len, + paddr >> PAGE_SHIFT, tsz, + vma->vm_page_prot)) + goto fail; + size -= tsz; + start += tsz; + len += tsz; + + if (size == 0) + return 0; + } + } + + return 0; +fail: + do_munmap(vma->vm_mm, vma->vm_start, len); + return -EAGAIN; +} +#else +static int mmap_vmcore(struct file *file, struct vm_area_struct *vma) +{ + return -ENOSYS; +} +#endif + static const struct file_operations proc_vmcore_operations = { .read = read_vmcore, .llseek = default_llseek, + .mmap = mmap_vmcore, }; static struct vmcore* __init get_new_element(void) @@ -348,7 +462,6 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz, Elf64_Ehdr *ehdr_ptr; Elf64_Phdr phdr; u64 phdr_sz = 0, note_off; - struct vm_struct *vm; ehdr_ptr = (Elf64_Ehdr *)elfptr; @@ -361,18 +474,10 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz, return rc; *notes_sz = roundup(phdr_sz, PAGE_SIZE); - *notes_buf = vzalloc(*notes_sz); + *notes_buf = alloc_elfnotes_buf(*notes_sz); if (!*notes_buf) return -ENOMEM; - /* - * Allow users to remap ELF note segment buffer on vmalloc memory using - * remap_vmalloc_range.() - */ - vm = find_vm_area(*notes_buf); - BUG_ON(!vm); - vm->flags |= VM_USERMAP; - rc = copy_notes_elf64(ehdr_ptr, *notes_buf); if (rc < 0) return rc; @@ -536,7 +641,6 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz, Elf32_Ehdr *ehdr_ptr; Elf32_Phdr phdr; u64 phdr_sz = 0, note_off; - struct vm_struct *vm; ehdr_ptr = (Elf32_Ehdr *)elfptr; @@ -549,18 +653,10 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz, return rc; *notes_sz = roundup(phdr_sz, PAGE_SIZE); - *notes_buf = vzalloc(*notes_sz); + *notes_buf = alloc_elfnotes_buf(*notes_sz); if (!*notes_buf) return -ENOMEM; - /* - * Allow users to remap ELF note segment buffer on vmalloc memory using - * remap_vmalloc_range() - */ - vm = find_vm_area(*notes_buf); - BUG_ON(!vm); - vm->flags |= VM_USERMAP; - rc = copy_notes_elf32(ehdr_ptr, *notes_buf); if (rc < 0) return rc; -- 2.20.1