[tip:x86/apic] x86/idt: Fix the X86_TRAP_BP gate

tip-bot for Ingo Molnar
2017-09-01T09:10:23Z

Commit-ID: c6ef89421e236d75693ae968d80d44a52409889d
Gitweb: http://git.kernel.org/tip/c6ef89421e236d75693ae968d80d44a52409889d
Author: Ingo Molnar <mingo@kernel.org>
AuthorDate: Fri, 1 Sep 2017 11:04:56 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 1 Sep 2017 11:04:56 +0200

x86/idt: Fix the X86_TRAP_BP gate

Andrei Vagin reported a CRIU regression and bisected it back to:

90f6225fba0c ("x86/idt: Move IST stack based traps to table init")

This table init conversion loses the system-gate property of X86_TRAP_BP
and erroneously moves it from DPL3 to DPL0.

Fix it.

Reported-by: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: dvlasenk@redhat.com
Cc: linux-tip-commits@vger.kernel.org
Cc: peterz@infradead.org
Cc: brgerst@gmail.com
Cc: rostedt@goodmis.org
Cc: bp@alien8.de
Cc: luto@kernel.org
Cc: jpoimboe@redhat.com
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: torvalds@linux-foundation.org
Cc: tip-bot for Jacob Shin <tipbot@zytor.com>
Link: http://lkml.kernel.org/r/20170901082630.xvyi5bwk6etmppqc@gmail.com

---
arch/x86/kernel/idt.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index 61b490c..6107ee1 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -44,6 +44,10 @@ struct idt_data {
#define ISTG(_vector, _addr, _ist) \
G(_vector, _addr, _ist, GATE_INTERRUPT, DPL0, __KERNEL_CS)

+/* System interrupt gate with interrupt stack */
+#define SISTG(_vector, _addr, _ist) \
+ G(_vector, _addr, _ist, GATE_INTERRUPT, DPL3, __KERNEL_CS)
+
/* Task gate */
#define TSKG(_vector, _gdt) \
G(_vector, NULL, DEFAULT_STACK, GATE_TASK, DPL0, _gdt << 3)
@@ -181,7 +185,7 @@ gate_desc debug_idt_table[IDT_ENTRIES] __page_aligned_bss;
static const __initdata struct idt_data ist_idts[] = {
ISTG(X86_TRAP_DB, debug, DEBUG_STACK),
ISTG(X86_TRAP_NMI, nmi, NMI_STACK),
- ISTG(X86_TRAP_BP, int3, DEBUG_STACK),
+ SISTG(X86_TRAP_BP, int3, DEBUG_STACK),
ISTG(X86_TRAP_DF, double_fault, DOUBLEFAULT_STACK),
#ifdef CONFIG_X86_MCE
ISTG(X86_TRAP_MC, &machine_check, MCE_STACK),