Commit 83086978 authored by HATAYAMA Daisuke's avatar HATAYAMA Daisuke Committed by Linus Torvalds
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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: default avatarHATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Acked-by: default avatarVivek 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: default avatarMaxim Uvarov <muvarov@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 591ff716

fs/proc/vmcore.c

+116 −20
Original line number Diff line number Diff line
@@ -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;

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