Commit-ID: 8cad6c58c9effb59b830bcf0103d8267ad2e312d Gitweb: https://git.kernel.org/tip/8cad6c58c9effb59b830bcf0103d8267ad2e312d Author: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> AuthorDate: Mon, 15 Oct 2018 16:09:29 +0200 Committer: Borislav Petkov <bp@xxxxxxx> 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 <jan.kiszka@xxxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Reviewed-by: Joerg Roedel <jroedel@xxxxxxx> Acked-by: Joerg Roedel <jroedel@xxxxxxx> CC: "H. Peter Anvin" <hpa@xxxxxxxxx> CC: Andrea Arcangeli <aarcange@xxxxxxxxxx> CC: Andy Lutomirski <luto@xxxxxxxxxx> CC: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> CC: Brian Gerst <brgerst@xxxxxxxxx> CC: Dave Hansen <dave.hansen@xxxxxxxxx> CC: David Laight <David.Laight@xxxxxxxxxx> CC: Denys Vlasenko <dvlasenk@xxxxxxxxxx> CC: Eduardo Valentin <eduval@xxxxxxxxxx> CC: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> CC: Ingo Molnar <mingo@xxxxxxxxxx> CC: Jiri Kosina <jkosina@xxxxxxx> CC: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> CC: Juergen Gross <jgross@xxxxxxxx> CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CC: Will Deacon <will.deacon@xxxxxxx> CC: aliguori@xxxxxxxxxx CC: daniel.gruss@xxxxxxxxxxxxxx CC: hughd@xxxxxxxxxx CC: keescook@xxxxxxxxxx CC: linux-mm <linux-mm@xxxxxxxxx> CC: x86-ml <x86@xxxxxxxxxx> Link: http://lkml.kernel.org/r/f271c747-1714-5a5b-a71f-ae189a093b8d@xxxxxxxxxxx --- 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
