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authorHATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>2013-07-03 15:02:23 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-07-03 16:07:30 -0700
commit83086978c63afd7c73e1c173c84aeab184c1e916 (patch)
tree423cb50415bfd2d3840272718591400e6a1f3b26
parent591ff71664e764a3806e341370f3c758cb2e7e3c (diff)
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 <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>
-rw-r--r--fs/proc/vmcore.c136
1 files 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 <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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