Commit-ID: 8cad6c58c9effb59b830bcf0103d8267ad2e312d
Gitweb: https://git.kernel.org/tip/8cad6c58c9effb59b830bcf0103d8267ad2e312d
Author: Jan Kiszka <[email protected]>
AuthorDate: Mon, 15 Oct 2018 16:09:29 +0200
Committer: Borislav Petkov <[email protected]>
CommitDate: Mon, 15 Oct 2018 16:54:28 +0200
x86/entry/32: Clear the CS high bits
Even if not on an entry stack, the CS's high bits must be
initialized because they are unconditionally evaluated in
PARANOID_EXIT_TO_KERNEL_MODE.
Failing to do so broke the boot on Galileo Gen2 and IOT2000 boards.
[ bp: Make the commit message tone passive and impartial. ]
Fixes: b92a165df17e ("x86/entry/32: Handle Entry from Kernel-Mode on
Entry-Stack")
Signed-off-by: Jan Kiszka <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Joerg Roedel <[email protected]>
Acked-by: Joerg Roedel <[email protected]>
CC: "H. Peter Anvin" <[email protected]>
CC: Andrea Arcangeli <[email protected]>
CC: Andy Lutomirski <[email protected]>
CC: Boris Ostrovsky <[email protected]>
CC: Brian Gerst <[email protected]>
CC: Dave Hansen <[email protected]>
CC: David Laight <[email protected]>
CC: Denys Vlasenko <[email protected]>
CC: Eduardo Valentin <[email protected]>
CC: Greg KH <[email protected]>
CC: Ingo Molnar <[email protected]>
CC: Jiri Kosina <[email protected]>
CC: Josh Poimboeuf <[email protected]>
CC: Juergen Gross <[email protected]>
CC: Linus Torvalds <[email protected]>
CC: Peter Zijlstra <[email protected]>
CC: Thomas Gleixner <[email protected]>
CC: Will Deacon <[email protected]>
CC: [email protected]
CC: [email protected]
CC: [email protected]
CC: [email protected]
CC: linux-mm <[email protected]>
CC: x86-ml <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
---
arch/x86/entry/entry_32.S | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 2767c625a52c..fbbf1ba57ec6 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -389,6 +389,13 @@
* that register for the time this macro runs
*/
+ /*
+ * The high bits of the CS dword (__csh) are used for
+ * CS_FROM_ENTRY_STACK and CS_FROM_USER_CR3. Clear them in case
+ * hardware didn't do this for us.
+ */
+ andl $(0x0000ffff), PT_CS(%esp)
+
/* Are we on the entry stack? Bail out if not! */
movl PER_CPU_VAR(cpu_entry_area), %ecx
addl $CPU_ENTRY_AREA_entry_stack + SIZEOF_entry_stack, %ecx
@@ -407,12 +414,6 @@
/* Load top of task-stack into %edi */
movl TSS_entry2task_stack(%edi), %edi
- /*
- * Clear unused upper bits of the dword containing the word-sized CS
- * slot in pt_regs in case hardware didn't clear it for us.
- */
- andl $(0x0000ffff), PT_CS(%esp)
-
/* Special case - entry from kernel mode via entry stack */
#ifdef CONFIG_VM86
movl PT_EFLAGS(%esp), %ecx # mix EFLAGS and CS
