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From 9d9dd47b77d859a1261ac0dc98d94018bb5bb6a0 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 3 Nov 2020 10:27:39 +0100
Subject: [PATCH 050/323] x86/crashdump/32: Simplify copy_oldmem_page()
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz
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>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
arch/x86/kernel/crash_dump_32.c | 48 +++++++--------------------------
1 file changed, 10 insertions(+), 38 deletions(-)
diff --git a/arch/x86/kernel/crash_dump_32.c b/arch/x86/kernel/crash_dump_32.c
index 33ee47670b99..5fcac46aaf6b 100644
--- a/arch/x86/kernel/crash_dump_32.c
+++ b/arch/x86/kernel/crash_dump_32.c
@@ -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;
}
- return csize;
-}
+ kunmap_local(vaddr);
-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;
+ return csize;
}
-arch_initcall(kdump_buf_page_init);
--
2.43.0
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