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Date: Fri, 7 Jun 2013 18:55:59 +0200
From: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
To: Vivek Goyal <vgoyal@...hat.com>
Cc: HATAYAMA Daisuke <d.hatayama@...fujitsu.com>,
Jan Willeke <willeke@...ibm.com>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
Heiko Carstens <heiko.carstens@...ibm.com>,
linux-kernel@...r.kernel.org, kexec@...ts.infradead.org
Subject: [PATCH v5 3/5] vmcore: Introduce remap_oldmem_pfn_range()
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 does the following:
* Check if /proc/vmcore page cache page is already available
* If yes:
- Return that page
* If no:
- Allocate new page
- Fill page using __vmcore_read()
- Add new page to page cache
Signed-off-by: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
---
fs/proc/vmcore.c | 94 ++++++++++++++++++++++++++++++++++++++++++----
include/linux/crash_dump.h | 3 ++
2 files changed, 89 insertions(+), 8 deletions(-)
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 221f84b..259a639 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -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 +154,36 @@ 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(target, src, size))
+ return -EFAULT;
+ return 0;
+ } 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 +200,7 @@ 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 +218,7 @@ 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 +234,7 @@ 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 +251,56 @@ 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(buffer, buflen, fpos, 1);
+}
+
+/*
+ * The vmcore fault handler uses the page cache and fills data using the
+ * standard __vmcore_read() function.
+ */
+static int mmap_vmcore_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+ struct address_space *mapping = vma->vm_private_data;
+ pgoff_t index = vmf->pgoff;
+ struct page *page;
+ loff_t src;
+ char *buf;
+ int rc;
+
+find_page:
+ page = find_lock_page(mapping, index);
+ if (page) {
+ unlock_page(page);
+ rc = VM_FAULT_MINOR;
+ } else {
+ page = page_cache_alloc_cold(mapping);
+ if (!page)
+ return VM_FAULT_OOM;
+ rc = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
+ if (rc) {
+ page_cache_release(page);
+ if (rc == -EEXIST)
+ goto find_page;
+ /* Probably ENOMEM for radix tree node */
+ return VM_FAULT_OOM;
+ }
+ buf = (void *) (page_to_pfn(page) << PAGE_SHIFT);
+ src = index << PAGE_CACHE_SHIFT;
+ __read_vmcore(buf, PAGE_SIZE, &src, 0);
+ unlock_page(page);
+ rc = VM_FAULT_MAJOR;
+ }
+ vmf->page = page;
+ return rc;
+}
+
+static const struct vm_operations_struct vmcore_mmap_ops = {
+ .fault = mmap_vmcore_fault,
+};
+
static int mmap_vmcore(struct file *file, struct vm_area_struct *vma)
{
size_t size = vma->vm_end - vma->vm_start;
@@ -242,6 +318,8 @@ 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;
+ vma->vm_private_data = file->f_mapping;
len = 0;
@@ -283,9 +361,9 @@ 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;
diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
index dd0f434..c0818de 100644
--- a/include/linux/crash_dump.h
+++ b/include/linux/crash_dump.h
@@ -16,6 +16,9 @@ extern int __weak elfcorehdr_alloc(void);
extern void __weak elfcorehdr_free(void);
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);
--
1.8.1.6
--
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