Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit b23e5844 authored by Zhenzhong Duan's avatar Zhenzhong Duan Committed by Juergen Gross
Browse files

xen/pv: Fix a boot up hang revealed by int3 self test 



Commit 7457c0da ("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: default avatarZhenzhong Duan <zhenzhong.duan@oracle.com>
Reviewed-by: default avatarJuergen 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: default avatarJuergen Gross <jgross@suse.com>
parent bef6e0ae

arch/x86/entry/entry_64.S

+0 −1
Original line number Diff line number Diff line
@@ -1176,7 +1176,6 @@ idtentry stack_segment do_stack_segment has_error_code=1 
#ifdef CONFIG_XEN_PV

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

arch/x86/include/asm/traps.h

+1 −1
Original line number Diff line number Diff line
@@ -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);

arch/x86/xen/enlighten_pv.c

+1 −1
Original line number Diff line number Diff line
@@ -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 },

#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 },

arch/x86/xen/xen-asm_64.S

+0 −1
Original line number Diff line number Diff line
@@ -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