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authorJuergen Gross <jgross@suse.com>2018-11-07 18:01:00 +0100
committerJuergen Gross <jgross@suse.com>2018-11-09 08:16:55 +0100
commit1457d8cf7664f34c4ba534c1073821a559a2f6f9 (patch)
treecb6435f561fe83789ecd108c5812e1e5667ae900 /arch
parent6cc4a0863c9709c512280c64e698d68443ac8053 (diff)
downloadlinux-1457d8cf7664f34c4ba534c1073821a559a2f6f9.tar.bz2
x86/xen: fix pv boot
Commit 9da3f2b7405440 ("x86/fault: BUG() when uaccess helpers fault on kernel addresses") introduced a regression for booting Xen PV guests. Xen PV guests are using __put_user() and __get_user() for accessing the p2m map (physical to machine frame number map) as accesses might fail in case of not populated areas of the map. With above commit using __put_user() and __get_user() for accessing kernel pages is no longer valid. So replace the Xen hack by adding appropriate p2m access functions using the default fixup handler. Fixes: 9da3f2b7405440 ("x86/fault: BUG() when uaccess helpers fault on kernel addresses") Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com> Signed-off-by: Juergen Gross <jgross@suse.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/include/asm/xen/page.h35
-rw-r--r--arch/x86/xen/p2m.c3
2 files changed, 32 insertions, 6 deletions
diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index 123e669bf363..790ce08e41f2 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -9,7 +9,7 @@
#include <linux/mm.h>
#include <linux/device.h>
-#include <linux/uaccess.h>
+#include <asm/extable.h>
#include <asm/page.h>
#include <asm/pgtable.h>
@@ -93,12 +93,39 @@ clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
*/
static inline int xen_safe_write_ulong(unsigned long *addr, unsigned long val)
{
- return __put_user(val, (unsigned long __user *)addr);
+ int ret = 0;
+
+ asm volatile("1: mov %[val], %[ptr]\n"
+ "2:\n"
+ ".section .fixup, \"ax\"\n"
+ "3: sub $1, %[ret]\n"
+ " jmp 2b\n"
+ ".previous\n"
+ _ASM_EXTABLE(1b, 3b)
+ : [ret] "+r" (ret), [ptr] "=m" (*addr)
+ : [val] "r" (val));
+
+ return ret;
}
-static inline int xen_safe_read_ulong(unsigned long *addr, unsigned long *val)
+static inline int xen_safe_read_ulong(const unsigned long *addr,
+ unsigned long *val)
{
- return __get_user(*val, (unsigned long __user *)addr);
+ int ret = 0;
+ unsigned long rval = ~0ul;
+
+ asm volatile("1: mov %[ptr], %[rval]\n"
+ "2:\n"
+ ".section .fixup, \"ax\"\n"
+ "3: sub $1, %[ret]\n"
+ " jmp 2b\n"
+ ".previous\n"
+ _ASM_EXTABLE(1b, 3b)
+ : [ret] "+r" (ret), [rval] "+r" (rval)
+ : [ptr] "m" (*addr));
+ *val = rval;
+
+ return ret;
}
#ifdef CONFIG_XEN_PV
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index d6d74efd8912..4fe84436d5a7 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -656,8 +656,7 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
/*
* The interface requires atomic updates on p2m elements.
- * xen_safe_write_ulong() is using __put_user which does an atomic
- * store via asm().
+ * xen_safe_write_ulong() is using an atomic store via asm().
*/
if (likely(!xen_safe_write_ulong(xen_p2m_addr + pfn, mfn)))
return true;