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x86/crashdump/32: Simplify copy_oldmem_page() 

Replace kmap_atomic_pfn() with kmap_local_pfn() which is preemptible and
can take page faults.

Remove the indirection of the dump page and the related cruft which is not
longer required.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20201118204007.670851839@linutronix.de
This commit is contained in:
Thomas Gleixner 2020-11-18 20:48:46 +01:00
parent e66f6e0954
commit 7e015a2798
1 changed files with 10 additions and 38 deletions
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48
arch/x86/kernel/crash_dump_32.c
View File

@ -13,8 +13,6 @@
#include <linux/uaccess.h>
static void *kdump_buf_page;
static inline bool is_crashed_pfn_valid(unsigned long pfn)
{
#ifndef CONFIG_X86_PAE
@ -41,15 +39,11 @@ static inline bool is_crashed_pfn_valid(unsigned long pfn)
* @userbuf: if set, @buf is in user address space, use copy_to_user(),
* otherwise @buf is in kernel address space, use memcpy().
*
* Copy a page from "oldmem". For this page, there is no pte mapped
* in the current kernel. We stitch up a pte, similar to kmap_atomic.
*
* Calling copy_to_user() in atomic context is not desirable. Hence first
* copying the data to a pre-allocated kernel page and then copying to user
* space in non-atomic context.
* Copy a page from "oldmem". For this page, there might be no pte mapped
* in the current kernel.
*/
ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
size_t csize, unsigned long offset, int userbuf)
ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
unsigned long offset, int userbuf)
{
void *vaddr;
@ -59,38 +53,16 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
if (!is_crashed_pfn_valid(pfn))
return -EFAULT;
vaddr = kmap_atomic_pfn(pfn);
vaddr = kmap_local_pfn(pfn);
if (!userbuf) {
memcpy(buf, (vaddr + offset), csize);
kunmap_atomic(vaddr);
memcpy(buf, vaddr + offset, csize);
} else {
if (!kdump_buf_page) {
printk(KERN_WARNING "Kdump: Kdump buffer page not"
" allocated\n");
kunmap_atomic(vaddr);
return -EFAULT;
}
copy_page(kdump_buf_page, vaddr);
kunmap_atomic(vaddr);
if (copy_to_user(buf, (kdump_buf_page + offset), csize))
return -EFAULT;
if (copy_to_user(buf, vaddr + offset, csize))
csize = -EFAULT;
}
kunmap_local(vaddr);
return csize;
}
static int __init kdump_buf_page_init(void)
{
int ret = 0;
kdump_buf_page = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!kdump_buf_page) {
printk(KERN_WARNING "Kdump: Failed to allocate kdump buffer"
" page\n");
ret = -ENOMEM;
}
return ret;
}
arch_initcall(kdump_buf_page_init);