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Zhenzhong Duan b23e5844df xen/pv: Fix a boot up hang revealed by int3 self test 
Commit 7457c0da02 ("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>
2019-07-17 08:09:59 +02:00
..
syscalls clone3-v5.3 2019-07-11 10:09:44 -07:00
vdso x86/vdso: Fix flip/flop vdso build bug 2019-07-12 17:35:07 +02:00
vsyscall Merge branch 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2019-07-08 21:48:15 -07:00
calling.h x86/fsgsbase: Revert FSGSBASE support 2019-07-03 16:35:23 +02:00
common.c arm64 updates for 5.3: 2019-07-08 09:54:55 -07:00
entry_32.S x86/entry/32: Fix ENDPROC of common_spurious 2019-07-09 14:41:03 +02:00
entry_64_compat.S x86/entry/64/compat: Fix stack switching for XEN PV 2019-01-18 00:39:33 +01:00
entry_64.S xen/pv: Fix a boot up hang revealed by int3 self test 2019-07-17 08:09:59 +02:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
syscall_32.c syscalls/x86: Unconditionally enable 'struct pt_regs' based syscalls on x86_64 2018-04-05 16:59:38 +02:00
syscall_64.c syscalls/x86: Unconditionally enable 'struct pt_regs' based syscalls on x86_64 2018-04-05 16:59:38 +02:00
thunk_32.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 474 2019-06-19 17:09:11 +02:00
thunk_64.S treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 474 2019-06-19 17:09:11 +02:00