linux-kernel - [RFC PATCH 11/14] powerpc/crash_dump: Use the new interface copy_oldmem_page

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Message-Id: <20211203104231.17597-12-amit.kachhap@arm.com>
Date:   Fri,  3 Dec 2021 16:12:28 +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>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc <linuxppc-dev@...ts.ozlabs.org>
Subject: [RFC PATCH 11/14] powerpc/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: Michael Ellerman <mpe@...erman.id.au>
CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: linuxppc <linuxppc-dev@...ts.ozlabs.org>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@....com>
---
 arch/powerpc/kernel/crash_dump.c | 33 ++++++++++++++++----------------
 1 file changed, 17 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/kernel/crash_dump.c b/arch/powerpc/kernel/crash_dump.c
index 5693e1c67c2b..a1c8a3a11694 100644
--- a/arch/powerpc/kernel/crash_dump.c
+++ b/arch/powerpc/kernel/crash_dump.c
@@ -68,33 +68,34 @@ void __init setup_kdump_trampoline(void)
 }
 #endif /* CONFIG_NONSTATIC_KERNEL */
 
-static size_t copy_oldmem_vaddr(void *vaddr, char *buf, size_t csize,
-                               unsigned long offset, int userbuf)
+static size_t copy_oldmem_vaddr(void *vaddr, char __user *ubuf, char *kbuf,
+				size_t csize, unsigned long offset)
 {
-	if (userbuf) {
-		if (copy_to_user((char __user *)buf, (vaddr + offset), csize))
+	if (ubuf) {
+		if (copy_to_user(ubuf, (vaddr + offset), csize))
 			return -EFAULT;
 	} else
-		memcpy(buf, (vaddr + offset), csize);
+		memcpy(kbuf, (vaddr + offset), csize);
 
 	return csize;
 }
 
 /**
- * copy_oldmem_page - copy one page from "oldmem"
+ * copy_oldmem_page_buf - copy one page from "oldmem"
  * @pfn: page frame number to be copied
- * @buf: target memory address for the copy; this can be in kernel address
- *      space or user address space (see @userbuf)
+ * @ubuf: target user memory address for the copy; use copy_to_user() if this
+ * address is present
+ * @kbuf: target kernel memory address for the copy; use memcpy() if this
+ * address is present
  * @csize: number of bytes to copy
  * @offset: offset in bytes into the page (based on pfn) to begin the copy
- * @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.
+ * Copy a page from "oldmem" into buffer pointed by either @ubuf or @kbuf. For
+ * this page, there is no pte mapped in the current kernel. We stitch up a pte,
+ * similar to kmap_atomic.
  */
-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;
 	phys_addr_t paddr;
@@ -107,10 +108,10 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
 
 	if (memblock_is_region_memory(paddr, csize)) {
 		vaddr = __va(paddr);
-		csize = copy_oldmem_vaddr(vaddr, buf, csize, offset, userbuf);
+		csize = copy_oldmem_vaddr(vaddr, ubuf, kbuf, csize, offset);
 	} else {
 		vaddr = ioremap_cache(paddr, PAGE_SIZE);
-		csize = copy_oldmem_vaddr(vaddr, buf, csize, offset, userbuf);
+		csize = copy_oldmem_vaddr(vaddr, ubuf, kbuf, csize, offset);
 		iounmap(vaddr);
 	}
 
-- 
2.17.1