Re: [PATCH] xen/pv: Fix a boot up hang triggered by int3 self test

From: Zhenzhong Duan
Date: Fri Jul 12 2019 - 03:42:26 EST

Sorry for the noise, it looks description is wrong.

This is not a double pop, but xen pv taking the path

with create_gap=0, I'll send a v2.


On 2019/7/11 12:47, Zhenzhong Duan wrote:
Commit 7457c0da024b ("x86/alternatives: Add int3_emulate_call()
selftest") reveals a bug in XEN PV int3 assemble code. There is
a double pop of register R11 and RCX currupting the exception
frame, one in xen_int3 and the other in xen_xenint3.

We see below hang at bootup:

general protection fault: 0000 [#1] SMP NOPTI
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.2.0+ #6
RIP: e030:int3_magic+0x0/0x7
Call Trace:

Fix it by removing xen_xenint3.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
arch/x86/include/asm/traps.h | 2 +-
arch/x86/xen/enlighten_pv.c | 2 +-
arch/x86/xen/xen-asm_64.S | 1 -
3 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index 7d6f3f3..f2bd284 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -40,7 +40,7 @@
asmlinkage void xen_divide_error(void);
asmlinkage void xen_xennmi(void);
asmlinkage void xen_xendebug(void);
-asmlinkage void xen_xenint3(void);
+asmlinkage void xen_int3(void);
asmlinkage void xen_overflow(void);
asmlinkage void xen_bounds(void);
asmlinkage void xen_invalid_op(void);
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 4722ba2..2138d69 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -596,7 +596,7 @@ struct trap_array_entry {
static struct trap_array_entry trap_array[] = {
{ debug, xen_xendebug, true },
- { int3, xen_xenint3, true },
+ { int3, xen_int3, true },
{ double_fault, xen_double_fault, true },
#ifdef CONFIG_X86_MCE
{ machine_check, xen_machine_check, true },
diff --git a/arch/x86/xen/xen-asm_64.S b/arch/x86/xen/xen-asm_64.S
index 1e9ef0b..ebf610b 100644
--- a/arch/x86/xen/xen-asm_64.S
+++ b/arch/x86/xen/xen-asm_64.S
@@ -32,7 +32,6 @@ xen_pv_trap divide_error
xen_pv_trap debug
xen_pv_trap xendebug
xen_pv_trap int3
-xen_pv_trap xenint3
xen_pv_trap xennmi
xen_pv_trap overflow
xen_pv_trap bounds