kdump, proc/vmcore: Enable kdumping encrypted memory with SME enabled

In the kdump kernel, the memory of the first kernel needs to be dumped
into the vmcore file.

If SME is enabled in the first kernel, the old memory has to be remapped
with the memory encryption mask in order to access it properly.

Split copy_oldmem_page() functionality to handle encrypted memory
properly.

 [ bp: Heavily massage everything. ]

Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: kexec@lists.infradead.org
Cc: tglx@linutronix.de
Cc: mingo@redhat.com
Cc: hpa@zytor.com
Cc: akpm@linux-foundation.org
Cc: dan.j.williams@intel.com
Cc: bhelgaas@google.com
Cc: baiyaowei@cmss.chinamobile.com
Cc: tiwai@suse.de
Cc: brijesh.singh@amd.com
Cc: dyoung@redhat.com
Cc: bhe@redhat.com
Cc: jroedel@suse.de
Link: https://lkml.kernel.org/r/be7b47f9-6be6-e0d1-2c2a-9125bc74b818@redhat.com

arch/x86/kernel/crash_dump_64.c

@@ -11,8 +11,38 @@
 #include <linux/uaccess.h>
 #include <linux/io.h>
 
+static ssize_t __copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
+				  unsigned long offset, int userbuf,
+				  bool encrypted)
+{
+	void  *vaddr;
+
+	if (!csize)
+		return 0;
+
+	if (encrypted)
+		vaddr = (__force void *)ioremap_encrypted(pfn << PAGE_SHIFT, PAGE_SIZE);
+	else
+		vaddr = (__force void *)ioremap_cache(pfn << PAGE_SHIFT, PAGE_SIZE);
+
+	if (!vaddr)
+		return -ENOMEM;
+
+	if (userbuf) {
+		if (copy_to_user((void __user *)buf, vaddr + offset, csize)) {
+			iounmap((void __iomem *)vaddr);
+			return -EFAULT;
+		}
+	} else
+		memcpy(buf, vaddr + offset, csize);
+
+	set_iounmap_nonlazy();
+	iounmap((void __iomem *)vaddr);
+	return csize;
+}
+
 /**
- * copy_oldmem_page - copy one page from "oldmem"
+ * copy_oldmem_page - copy one page of memory
  * @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)
@@ -21,30 +51,22 @@
  * @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 the old kernel's memory. 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(unsigned long pfn, char *buf, size_t csize,
+			 unsigned long offset, int userbuf)
 {
-	void  *vaddr;
-
-	if (!csize)
-		return 0;
-
-	vaddr = ioremap_cache(pfn << PAGE_SHIFT, PAGE_SIZE);
-	if (!vaddr)
-		return -ENOMEM;
-
-	if (userbuf) {
-		if (copy_to_user(buf, vaddr + offset, csize)) {
-			iounmap(vaddr);
-			return -EFAULT;
-		}
-	} else
-		memcpy(buf, vaddr + offset, csize);
-
-	set_iounmap_nonlazy();
-	iounmap(vaddr);
-	return csize;
+	return __copy_oldmem_page(pfn, buf, csize, offset, userbuf, false);
+}
+
+/**
+ * copy_oldmem_page_encrypted - same as copy_oldmem_page() above but ioremap the
+ * memory with the encryption mask set to accomodate kdump on SME-enabled
+ * machines.
+ */
+ssize_t copy_oldmem_page_encrypted(unsigned long pfn, char *buf, size_t csize,
+				   unsigned long offset, int userbuf)
+{
+	return __copy_oldmem_page(pfn, buf, csize, offset, userbuf, true);
 }

fs/proc/vmcore.c

@@ -24,6 +24,8 @@
 #include <linux/vmalloc.h>
 #include <linux/pagemap.h>
 #include <linux/uaccess.h>
+#include <linux/mem_encrypt.h>
+#include <asm/pgtable.h>
 #include <asm/io.h>
 #include "internal.h"
 
@@ -98,7 +100,8 @@ static int pfn_is_ram(unsigned long pfn)
 
 /* Reads a page from the oldmem device from given offset. */
 static ssize_t read_from_oldmem(char *buf, size_t count,
-				u64 *ppos, int userbuf)
+				u64 *ppos, int userbuf,
+				bool encrypted)
 {
 	unsigned long pfn, offset;
 	size_t nr_bytes;
@@ -120,8 +123,15 @@ static ssize_t read_from_oldmem(char *buf, size_t count,
 		if (pfn_is_ram(pfn) == 0)
 			memset(buf, 0, nr_bytes);
 		else {
-			tmp = copy_oldmem_page(pfn, buf, nr_bytes,
-						offset, userbuf);
+			if (encrypted)
+				tmp = copy_oldmem_page_encrypted(pfn, buf,
+								 nr_bytes,
+								 offset,
+								 userbuf);
+			else
+				tmp = copy_oldmem_page(pfn, buf, nr_bytes,
+						       offset, userbuf);
+
 			if (tmp < 0)
 				return tmp;
 		}
@@ -155,7 +165,7 @@ void __weak elfcorehdr_free(unsigned long long addr)
  */
 ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos)
 {
-	return read_from_oldmem(buf, count, ppos, 0);
+	return read_from_oldmem(buf, count, ppos, 0, false);
 }
 
 /*
@@ -163,7 +173,7 @@ ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos)
  */
 ssize_t __weak elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos)
 {
-	return read_from_oldmem(buf, count, ppos, 0);
+	return read_from_oldmem(buf, count, ppos, 0, sme_active());
 }
 
 /*
@@ -173,6 +183,7 @@ int __weak remap_oldmem_pfn_range(struct vm_area_struct *vma,
 				  unsigned long from, unsigned long pfn,
 				  unsigned long size, pgprot_t prot)
 {
+	prot = pgprot_encrypted(prot);
 	return remap_pfn_range(vma, from, pfn, size, prot);
 }
 
@@ -351,7 +362,8 @@ static ssize_t __read_vmcore(char *buffer, size_t buflen, loff_t *fpos,
 					    m->offset + m->size - *fpos,
 					    buflen);
 			start = m->paddr + *fpos - m->offset;
-			tmp = read_from_oldmem(buffer, tsz, &start, userbuf);
+			tmp = read_from_oldmem(buffer, tsz, &start,
+					       userbuf, sme_active());
 			if (tmp < 0)
 				return tmp;
 			buflen -= tsz;

include/linux/crash_dump.h

@@ -26,6 +26,10 @@ extern int remap_oldmem_pfn_range(struct vm_area_struct *vma,
 
 extern ssize_t copy_oldmem_page(unsigned long, char *, size_t,
 						unsigned long, int);
+extern ssize_t copy_oldmem_page_encrypted(unsigned long pfn, char *buf,
+					  size_t csize, unsigned long offset,
+					  int userbuf);
+
 void vmcore_cleanup(void);
 
 /* Architecture code defines this if there are other possible ELF