Hello,
This patch fixes the issue reported by Amd on an overlook of no-MMU
configuration.
This patch is made on top of v3.10-rc4-mmotm-2013-06-06-16-19.
I tested this on x86_64 and x86 with 1GB and 5GB memory.
I build this on arm without CONFIG_MMU configuration.
Thanks.
HATAYAMA, Daisuke
>From e2f067a497872a9c60002c56ea550e4600072166 Mon Sep 17 00:00:00 2001
From: HATAYAMA Daisuke <d.hatay...@jp.fujitsu.com>
Date: Sat, 8 Jun 2013 20:46:57 +0900
Subject: [PATCH] vmcore: disable mmap_vmcore() if CONFIG_MMU is not defined
>From Amd's report of a link-time build error in vmcore.c, it turned
out that mmap_vmcore() work overlooked no-MMU configuraiton.
In the current design, it's impossible to implement mmap_vmcore() for
no-MMU configuration since MMU is essential 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.
Hence, this patch disables mmap_vmcore() if CONFIG_MMU is not defined,
returning -ENOSYS.
Another change is to fix the build error by using vmalloc_user()
instead of calling vzalloc() and find_vm_area() in order, by which we
no longer need to call find_vm_area() in vmcore.c that has no
counterpart on non-MMU configuration.
Also, on no-MMU configuration, because we don't export buffer for ELF
note segment to user-space, we use vzalloc() to allocate the buffer.
Therefore, we use differnet functions to allocate the buffer for ELF
note segment. To avoid code duplication, introduce a helper
alloc_elfnotes_buf().
Reported-by: Amd Bergmann <a...@arndb.de>
Signed-off-by: HATAYAMA Daisuke <d.hatay...@jp.fujitsu.com>
---
fs/proc/vmcore.c | 57 +++++++++++++++++++++++++++++++++++------------------
1 files changed, 37 insertions(+), 20 deletions(-)
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 0f6db52..2850317 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -195,6 +195,35 @@ 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;
@@ -271,6 +300,12 @@ 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,
@@ -427,7 +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;
@@ -440,18 +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;
@@ -615,7 +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;
@@ -628,18 +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;
--
1.7.7.6
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