From: Zhenzhong Duan zhenzhong.duan@oracle.com
[ Upstream commit b23e5844dfe78a80ba672793187d3f52e4b528d7 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/entry/entry_64.S | 1 - arch/x86/include/asm/traps.h | 2 +- arch/x86/xen/enlighten_pv.c | 2 +- arch/x86/xen/xen-asm_64.S | 1 - 4 files changed, 2 insertions(+), 4 deletions(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index e09ba4bc8b98..b2524d349595 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1113,7 +1113,6 @@ idtentry stack_segment do_stack_segment has_error_code=1 #ifdef CONFIG_XEN idtentry xennmi do_nmi has_error_code=0 idtentry xendebug do_debug has_error_code=0 -idtentry xenint3 do_int3 has_error_code=0 #endif
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 afbc87206886..b771bb3d159b 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 481d7920ea24..f79a0cdc6b4e 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -598,12 +598,12 @@ 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 }, #endif { nmi, xen_xennmi, true }, + { int3, xen_int3, false }, { overflow, xen_overflow, false }, #ifdef CONFIG_IA32_EMULATION { 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 417b339e5c8e..3a6feed76dfc 100644 --- a/arch/x86/xen/xen-asm_64.S +++ b/arch/x86/xen/xen-asm_64.S @@ -30,7 +30,6 @@ 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