| Message ID | 1563095732-16700-1-git-send-email-zhenzhong.duan@oracle.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 976634fb10b41c8521018f69afaaccc4d24d5f2d |
| Headers | show |
| Series | [v3] xen/pv: Fix a boot up hang revealed by int3 self test | expand |
On 14.07.19 11:15, Zhenzhong Duan wrote: > 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> Juergen
On 14.07.19 11:15, Zhenzhong Duan wrote: > 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> Pushed to xen/tip.git for-linus-5.3a Juergen
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 0ea4831..35a66fc 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 #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 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..30c14cb 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 }, #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 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
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> 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> --- bootup test pass with PV guest. v3: set ist_okay to false for int3 per PeterZ add Andrew's comments to patch description v2: fix up description. --- 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(-)