From 6778948f9de86c3cfaf36725a7c87dcff9ba247f Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Mon, 11 Dec 2023 08:20:59 +0000
Subject: [PATCH] kernel_5.10 no rt
---
kernel/arch/mips/kernel/crash_dump.c | 42 +++++++++++++++++++++++++++++++++++-------
1 files changed, 35 insertions(+), 7 deletions(-)
diff --git a/kernel/arch/mips/kernel/crash_dump.c b/kernel/arch/mips/kernel/crash_dump.c
index 9aba83e..01b2bd9 100644
--- a/kernel/arch/mips/kernel/crash_dump.c
+++ b/kernel/arch/mips/kernel/crash_dump.c
@@ -5,6 +5,8 @@
#include <linux/uaccess.h>
#include <linux/slab.h>
+static void *kdump_buf_page;
+
/**
* copy_oldmem_page - copy one page from "oldmem"
* @pfn: page frame number to be copied
@@ -15,25 +17,51 @@
* @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 might be no pte mapped
+ * Copy a page from "oldmem". For this page, there is no pte mapped
* in the current kernel.
+ *
+ * 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.
*/
-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;
if (!csize)
return 0;
- vaddr = kmap_local_pfn(pfn);
+ vaddr = kmap_atomic_pfn(pfn);
if (!userbuf) {
- memcpy(buf, vaddr + offset, csize);
+ memcpy(buf, (vaddr + offset), csize);
+ kunmap_atomic(vaddr);
} else {
- if (copy_to_user(buf, vaddr + offset, csize))
- csize = -EFAULT;
+ if (!kdump_buf_page) {
+ pr_warn("Kdump: Kdump buffer page not allocated\n");
+
+ return -EFAULT;
+ }
+ copy_page(kdump_buf_page, vaddr);
+ kunmap_atomic(vaddr);
+ if (copy_to_user(buf, (kdump_buf_page + offset), csize))
+ return -EFAULT;
}
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) {
+ pr_warn("Kdump: Failed to allocate kdump buffer page\n");
+ ret = -ENOMEM;
+ }
+
+ return ret;
+}
+arch_initcall(kdump_buf_page_init);
--
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