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authorZhenzhong Duan <zhenzhong.duan@oracle.com>2019-07-14 17:15:32 +0800
committerJuergen Gross <jgross@suse.com>2019-07-17 08:09:59 +0200
commitb23e5844dfe78a80ba672793187d3f52e4b528d7 (patch)
parentbef6e0ae7420bfddfb150dda529bbe835f87b9f2 (diff)
xen/pv: Fix a boot up hang revealed by int3 self test
Commit 7457c0da024b ("x86/alternatives: Add int3_emulate_call() selftest") is used to ensure there is a gap setup in int3 exception stack which could be used for inserting call return address. This gap is missed in XEN PV int3 exception entry path, then below panic triggered: [ 0.772876] general protection fault: 0000 [#1] SMP NOPTI [ 0.772886] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.2.0+ #11 [ 0.772893] RIP: e030:int3_magic+0x0/0x7 [ 0.772905] RSP: 3507:ffffffff82203e98 EFLAGS: 00000246 [ 0.773334] Call Trace: [ 0.773334] alternative_instructions+0x3d/0x12e [ 0.773334] check_bugs+0x7c9/0x887 [ 0.773334] ? __get_locked_pte+0x178/0x1f0 [ 0.773334] start_kernel+0x4ff/0x535 [ 0.773334] ? set_init_arg+0x55/0x55 [ 0.773334] xen_start_kernel+0x571/0x57a For 64bit PV guests, Xen's ABI enters the kernel with using SYSRET, with %rcx/%r11 on the stack. To convert back to "normal" looking exceptions, the xen thunks do 'xen_*: pop %rcx; pop %r11; jmp *'. E.g. Extracting 'xen_pv_trap xenint3' we have: xen_xenint3: pop %rcx; pop %r11; jmp xenint3 As xenint3 and int3 entry code are same except xenint3 doesn't generate a gap, we can fix it by using int3 and drop useless xenint3. Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com> Reviewed-by: Juergen Gross <jgross@suse.com> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Juergen Gross <jgross@suse.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Andrew Cooper <andrew.cooper3@citrix.com> Signed-off-by: Juergen Gross <jgross@suse.com>
4 files changed, 2 insertions, 4 deletions
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 0ea4831a72a4..35a66fcfcb91 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1176,7 +1176,6 @@ idtentry stack_segment do_stack_segment has_error_code=1
idtentry xennmi do_nmi has_error_code=0
idtentry xendebug do_debug has_error_code=0
-idtentry xenint3 do_int3 has_error_code=0
idtentry general_protection do_general_protection has_error_code=1
diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index 7d6f3f3fad78..f2bd284abc16 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -40,7 +40,7 @@ asmlinkage void simd_coprocessor_error(void);
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 5d16824e4dca..bed6bb93c965 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -596,12 +596,12 @@ struct trap_array_entry {
static struct trap_array_entry trap_array[] = {
{ debug, xen_xendebug, true },
- { int3, xen_xenint3, true },
{ double_fault, xen_double_fault, true },
#ifdef CONFIG_X86_MCE
{ machine_check, xen_machine_check, true },
{ nmi, xen_xennmi, true },
+ { int3, xen_int3, false },
{ overflow, xen_overflow, false },
{ entry_INT80_compat, xen_entry_INT80_compat, false },
diff --git a/arch/x86/xen/xen-asm_64.S b/arch/x86/xen/xen-asm_64.S
index 1e9ef0ba30a5..ebf610b49c06 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