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vmcore: introduce remap_oldmem_pfn_range()

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For zfcpdump we can't map the HSA storage because it is only available via
a read interface.  Therefore, for the new vmcore mmap feature we have
introduce a new mechanism to create mappings on demand.

This patch introduces a new architecture function remap_oldmem_pfn_range()
that should be used to create mappings with remap_pfn_range() for oldmem
areas that can be directly mapped.  For zfcpdump this is everything
besides of the HSA memory.  For the areas that are not mapped by
remap_oldmem_pfn_range() a generic vmcore a new generic vmcore fault
handler mmap_vmcore_fault() is called.

This handler works as follows:

* Get already available or new page from page cache (find_or_create_page)
* Check if /proc/vmcore page is filled with data (PageUptodate)
* If yes:
  Return that page
* If no:
  Fill page using __vmcore_read(), set PageUptodate, and return page

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Cc: Jan Willeke <willeke@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Michael Holzheu 2013-09-11 14:24:51 -07:00 committed by Linus Torvalds
parent 97b0f6f9cd
commit 9cb218131d
2 changed files with 86 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

91
fs/proc/vmcore.c
View File

@ -21,6 +21,7 @@
#include <linux/crash_dump.h>
#include <linux/list.h>
#include <linux/vmalloc.h>
#include <linux/pagemap.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include "internal.h"
@ -153,11 +154,35 @@ ssize_t __weak elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos)
return read_from_oldmem(buf, count, ppos, 0);
}
/*
* Architectures may override this function to map oldmem
*/
int __weak remap_oldmem_pfn_range(struct vm_area_struct *vma,
unsigned long from, unsigned long pfn,
unsigned long size, pgprot_t prot)
{
return remap_pfn_range(vma, from, pfn, size, prot);
}
/*
* Copy to either kernel or user space
*/
static int copy_to(void *target, void *src, size_t size, int userbuf)
{
if (userbuf) {
if (copy_to_user((char __user *) target, src, size))
return -EFAULT;
} else {
memcpy(target, src, size);
}
return 0;
}
/* Read from the ELF header and then the crash dump. On error, negative value is
* returned otherwise number of bytes read are returned.
*/
static ssize_t read_vmcore(struct file *file, char __user *buffer,
size_t buflen, loff_t *fpos)
static ssize_t __read_vmcore(char *buffer, size_t buflen, loff_t *fpos,
int userbuf)
{
ssize_t acc = 0, tmp;
size_t tsz;
@ -174,7 +199,7 @@ static ssize_t read_vmcore(struct file *file, char __user *buffer,
/* Read ELF core header */
if (*fpos < elfcorebuf_sz) {
tsz = min(elfcorebuf_sz - (size_t)*fpos, buflen);
if (copy_to_user(buffer, elfcorebuf + *fpos, tsz))
if (copy_to(buffer, elfcorebuf + *fpos, tsz, userbuf))
return -EFAULT;
buflen -= tsz;
*fpos += tsz;
@ -192,7 +217,7 @@ static ssize_t read_vmcore(struct file *file, char __user *buffer,
tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, buflen);
kaddr = elfnotes_buf + *fpos - elfcorebuf_sz;
if (copy_to_user(buffer, kaddr, tsz))
if (copy_to(buffer, kaddr, tsz, userbuf))
return -EFAULT;
buflen -= tsz;
*fpos += tsz;
@ -208,7 +233,7 @@ static ssize_t read_vmcore(struct file *file, char __user *buffer,
if (*fpos < m->offset + m->size) {
tsz = min_t(size_t, m->offset + m->size - *fpos, buflen);
start = m->paddr + *fpos - m->offset;
tmp = read_from_oldmem(buffer, tsz, &start, 1);
tmp = read_from_oldmem(buffer, tsz, &start, userbuf);
if (tmp < 0)
return tmp;
buflen -= tsz;
@ -225,6 +250,55 @@ static ssize_t read_vmcore(struct file *file, char __user *buffer,
return acc;
}
static ssize_t read_vmcore(struct file *file, char __user *buffer,
size_t buflen, loff_t *fpos)
{
return __read_vmcore((__force char *) buffer, buflen, fpos, 1);
}
/*
* The vmcore fault handler uses the page cache and fills data using the
* standard __vmcore_read() function.
*
* On s390 the fault handler is used for memory regions that can't be mapped
* directly with remap_pfn_range().
*/
static int mmap_vmcore_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
#ifdef CONFIG_S390
struct address_space *mapping = vma->vm_file->f_mapping;
pgoff_t index = vmf->pgoff;
struct page *page;
loff_t offset;
char *buf;
int rc;
page = find_or_create_page(mapping, index, GFP_KERNEL);
if (!page)
return VM_FAULT_OOM;
if (!PageUptodate(page)) {
offset = (loff_t) index << PAGE_CACHE_SHIFT;
buf = __va((page_to_pfn(page) << PAGE_SHIFT));
rc = __read_vmcore(buf, PAGE_SIZE, &offset, 0);
if (rc < 0) {
unlock_page(page);
page_cache_release(page);
return (rc == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS;
}
SetPageUptodate(page);
}
unlock_page(page);
vmf->page = page;
return 0;
#else
return VM_FAULT_SIGBUS;
#endif
}
static const struct vm_operations_struct vmcore_mmap_ops = {
.fault = mmap_vmcore_fault,
};
/**
* alloc_elfnotes_buf - allocate buffer for ELF note segment in
* vmalloc memory
@ -271,6 +345,7 @@ static int mmap_vmcore(struct file *file, struct vm_area_struct *vma)
vma->vm_flags &= ~(VM_MAYWRITE | VM_MAYEXEC);
vma->vm_flags |= VM_MIXEDMAP;
vma->vm_ops = &vmcore_mmap_ops;
len = 0;
@ -312,9 +387,9 @@ static int mmap_vmcore(struct file *file, struct vm_area_struct *vma)
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))
if (remap_oldmem_pfn_range(vma, vma->vm_start + len,
paddr >> PAGE_SHIFT, tsz,
vma->vm_page_prot))
goto fail;
size -= tsz;
start += tsz;

3
include/linux/crash_dump.h
View File

@ -17,6 +17,9 @@ extern int __weak elfcorehdr_alloc(unsigned long long *addr,
extern void __weak elfcorehdr_free(unsigned long long addr);
extern ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos);
extern ssize_t __weak elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos);
extern int __weak remap_oldmem_pfn_range(struct vm_area_struct *vma,
unsigned long from, unsigned long pfn,
unsigned long size, pgprot_t prot);
extern ssize_t copy_oldmem_page(unsigned long, char *, size_t,
unsigned long, int);