linux-kernel - [RFC PATCH 10/14] riscv/crash_dump: Use the new interface copy_oldmem_page

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Message-Id: <20211203104231.17597-11-amit.kachhap@arm.com>
Date:   Fri,  3 Dec 2021 16:12:27 +0530
From:   Amit Daniel Kachhap <amit.kachhap@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Christoph Hellwig <hch@....de>,
        Vincenzo Frascino <Vincenzo.Frascino@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        kexec <kexec@...ts.infradead.org>,
        Amit Daniel Kachhap <amit.kachhap@....com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv <linux-riscv@...ts.infradead.org>
Subject: [RFC PATCH 10/14] riscv/crash_dump: Use the new interface copy_oldmem_page_buf

The current interface copy_oldmem_page() passes user pointer without
__user annotation and hence does unnecessary user/kernel pointer
conversions during its implementation.

Use the interface copy_oldmem_page_buf() to avoid this issue.

Cc: Paul Walmsley <paul.walmsley@...ive.com>
Cc: Palmer Dabbelt <palmer@...ive.com>
Cc: Albert Ou <aou@...s.berkeley.edu>
Cc: linux-riscv <linux-riscv@...ts.infradead.org>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@....com>
---
 arch/riscv/kernel/crash_dump.c | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/arch/riscv/kernel/crash_dump.c b/arch/riscv/kernel/crash_dump.c
index 86cc0ada5752..3a8fadcd1278 100644
--- a/arch/riscv/kernel/crash_dump.c
+++ b/arch/riscv/kernel/crash_dump.c
@@ -9,20 +9,21 @@
 #include <linux/io.h>
 
 /**
- * copy_oldmem_page() - copy one page from old kernel memory
+ * copy_oldmem_page_buf() - copy one page from old kernel memory
  * @pfn: page frame number to be copied
- * @buf: buffer where the copied page is placed
+ * @ubuf: user buffer where the copied page is placed; use copy_to_user() if
+ * this pointer is not NULL
+ * @kbuf: kernel buffer where the copied page is placed; use memcpy() if this
+ * pointer is not NULL
  * @csize: number of bytes to copy
  * @offset: offset in bytes into the page
- * @userbuf: if set, @buf is in a user address space
  *
- * This function copies one page from old kernel memory into buffer pointed by
- * @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes
- * copied or negative error in case of failure.
+ * This function copies one page from old kernel memory into the buffer pointed
+ * by either @ubuf or @kbuf. Returns number of bytes copied or negative error in
+ * case of failure.
  */
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
-			 size_t csize, unsigned long offset,
-			 int userbuf)
+ssize_t copy_oldmem_page_buf(unsigned long pfn, char __user *ubuf, char *kbuf,
+			     size_t csize, unsigned long offset)
 {
 	void *vaddr;
 
@@ -33,13 +34,13 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
 	if (!vaddr)
 		return -ENOMEM;
 
-	if (userbuf) {
-		if (copy_to_user((char __user *)buf, vaddr + offset, csize)) {
+	if (ubuf) {
+		if (copy_to_user(ubuf, vaddr + offset, csize)) {
 			memunmap(vaddr);
 			return -EFAULT;
 		}
 	} else
-		memcpy(buf, vaddr + offset, csize);
+		memcpy(kbuf, vaddr + offset, csize);
 
 	memunmap(vaddr);
 	return csize;
-- 
2.17.1