From: Michael Ellerman <michael@ellerman.id.au>
Date: Thu, 31 Jul 2008 06:54:28 +0000 (+1000)
Subject: powerpc: Fix /dev/oldmem interface for kdump
X-Git-Tag: v2.6.27-rc4~31^2~2
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7230ced4925b07c259a62b515d8278c6bb1ad98c;p=linux-2.6

powerpc: Fix /dev/oldmem interface for kdump

A change to __ioremap() broke reading /dev/oldmem because we're no
longer able to ioremap pfn 0 (d177c207, "[PATCH] powerpc: IOMMU: don't
ioremap null addresses").

We actually don't need to ioremap for anything that's part of the linear
mapping, so just read it directly.

Also make sure we're only reading one page or less at a time.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Sachin Sant <sachinp@in.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
---

diff --git a/arch/powerpc/kernel/crash_dump.c b/arch/powerpc/kernel/crash_dump.c
index e0debcca0b..a323c9b32e 100644
--- a/arch/powerpc/kernel/crash_dump.c
+++ b/arch/powerpc/kernel/crash_dump.c
@@ -86,6 +86,19 @@ static int __init parse_savemaxmem(char *p)
 }
 __setup("savemaxmem=", parse_savemaxmem);
 
+
+static size_t copy_oldmem_vaddr(void *vaddr, char *buf, size_t csize,
+                               unsigned long offset, int userbuf)
+{
+	if (userbuf) {
+		if (copy_to_user((char __user *)buf, (vaddr + offset), csize))
+			return -EFAULT;
+	} else
+		memcpy(buf, (vaddr + offset), csize);
+
+	return csize;
+}
+
 /**
  * copy_oldmem_page - copy one page from "oldmem"
  * @pfn: page frame number to be copied
@@ -107,16 +120,16 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
 	if (!csize)
 		return 0;
 
-	vaddr = __ioremap(pfn << PAGE_SHIFT, PAGE_SIZE, 0);
+	csize = min(csize, PAGE_SIZE);
 
-	if (userbuf) {
-		if (copy_to_user((char __user *)buf, (vaddr + offset), csize)) {
-			iounmap(vaddr);
-			return -EFAULT;
-		}
-	} else
-		memcpy(buf, (vaddr + offset), csize);
+	if (pfn < max_pfn) {
+		vaddr = __va(pfn << PAGE_SHIFT);
+		csize = copy_oldmem_vaddr(vaddr, buf, csize, offset, userbuf);
+	} else {
+		vaddr = __ioremap(pfn << PAGE_SHIFT, PAGE_SIZE, 0);
+		csize = copy_oldmem_vaddr(vaddr, buf, csize, offset, userbuf);
+		iounmap(vaddr);
+	}
 
-	iounmap(vaddr);
 	return csize;
 }