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vmcore: support mmap() on /proc/vmcore

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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 <d.hatayama@jp.fujitsu.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
Cc: Lisa Mitchell <lisa.mitchell@hp.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Tested-by: Maxim Uvarov <muvarov@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
HATAYAMA Daisuke 2013-07-03 15:02:23 -07:00 • committed by Linus Torvalds
commit 83086978c6
1 changed files with 116 additions and 20 deletions
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136
fs/proc/vmcore.c
View file

@ -20,6 +20,7 @@
#include <linux/init.h>
#include <linux/crash_dump.h>
#include <linux/list.h>
#include <linux/vmalloc.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#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;