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b23e5844df
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>
180 lines
3.8 KiB
ArmAsm
180 lines
3.8 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Asm versions of Xen pv-ops, suitable for direct use.
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*
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* We only bother with direct forms (ie, vcpu in pda) of the
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* operations here; the indirect forms are better handled in C.
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*/
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#include <asm/errno.h>
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#include <asm/percpu.h>
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#include <asm/processor-flags.h>
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#include <asm/segment.h>
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#include <asm/asm-offsets.h>
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#include <asm/thread_info.h>
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#include <asm/asm.h>
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#include <xen/interface/xen.h>
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#include <linux/init.h>
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#include <linux/linkage.h>
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.macro xen_pv_trap name
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ENTRY(xen_\name)
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pop %rcx
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pop %r11
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jmp \name
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END(xen_\name)
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_ASM_NOKPROBE(xen_\name)
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.endm
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xen_pv_trap divide_error
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xen_pv_trap debug
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xen_pv_trap xendebug
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xen_pv_trap int3
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xen_pv_trap xennmi
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xen_pv_trap overflow
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xen_pv_trap bounds
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xen_pv_trap invalid_op
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xen_pv_trap device_not_available
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xen_pv_trap double_fault
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xen_pv_trap coprocessor_segment_overrun
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xen_pv_trap invalid_TSS
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xen_pv_trap segment_not_present
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xen_pv_trap stack_segment
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xen_pv_trap general_protection
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xen_pv_trap page_fault
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xen_pv_trap spurious_interrupt_bug
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xen_pv_trap coprocessor_error
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xen_pv_trap alignment_check
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#ifdef CONFIG_X86_MCE
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xen_pv_trap machine_check
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#endif /* CONFIG_X86_MCE */
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xen_pv_trap simd_coprocessor_error
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#ifdef CONFIG_IA32_EMULATION
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xen_pv_trap entry_INT80_compat
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#endif
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xen_pv_trap hypervisor_callback
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__INIT
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ENTRY(xen_early_idt_handler_array)
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i = 0
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.rept NUM_EXCEPTION_VECTORS
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pop %rcx
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pop %r11
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jmp early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE
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i = i + 1
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.fill xen_early_idt_handler_array + i*XEN_EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
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.endr
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END(xen_early_idt_handler_array)
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__FINIT
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hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32
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/*
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* Xen64 iret frame:
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*
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* ss
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* rsp
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* rflags
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* cs
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* rip <-- standard iret frame
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*
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* flags
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*
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* rcx }
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* r11 }<-- pushed by hypercall page
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* rsp->rax }
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*/
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ENTRY(xen_iret)
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pushq $0
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jmp hypercall_iret
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ENTRY(xen_sysret64)
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/*
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* We're already on the usermode stack at this point, but
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* still with the kernel gs, so we can easily switch back.
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*
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* tss.sp2 is scratch space.
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*/
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movq %rsp, PER_CPU_VAR(cpu_tss_rw + TSS_sp2)
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movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
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pushq $__USER_DS
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pushq PER_CPU_VAR(cpu_tss_rw + TSS_sp2)
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pushq %r11
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pushq $__USER_CS
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pushq %rcx
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pushq $VGCF_in_syscall
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jmp hypercall_iret
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/*
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* Xen handles syscall callbacks much like ordinary exceptions, which
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* means we have:
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* - kernel gs
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* - kernel rsp
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* - an iret-like stack frame on the stack (including rcx and r11):
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* ss
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* rsp
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* rflags
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* cs
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* rip
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* r11
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* rsp->rcx
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*/
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/* Normal 64-bit system call target */
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ENTRY(xen_syscall_target)
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popq %rcx
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popq %r11
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/*
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* Neither Xen nor the kernel really knows what the old SS and
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* CS were. The kernel expects __USER_DS and __USER_CS, so
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* report those values even though Xen will guess its own values.
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*/
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movq $__USER_DS, 4*8(%rsp)
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movq $__USER_CS, 1*8(%rsp)
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jmp entry_SYSCALL_64_after_hwframe
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ENDPROC(xen_syscall_target)
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#ifdef CONFIG_IA32_EMULATION
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/* 32-bit compat syscall target */
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ENTRY(xen_syscall32_target)
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popq %rcx
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popq %r11
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/*
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* Neither Xen nor the kernel really knows what the old SS and
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* CS were. The kernel expects __USER32_DS and __USER32_CS, so
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* report those values even though Xen will guess its own values.
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*/
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movq $__USER32_DS, 4*8(%rsp)
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movq $__USER32_CS, 1*8(%rsp)
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jmp entry_SYSCALL_compat_after_hwframe
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ENDPROC(xen_syscall32_target)
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/* 32-bit compat sysenter target */
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ENTRY(xen_sysenter_target)
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mov 0*8(%rsp), %rcx
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mov 1*8(%rsp), %r11
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mov 5*8(%rsp), %rsp
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jmp entry_SYSENTER_compat
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ENDPROC(xen_sysenter_target)
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#else /* !CONFIG_IA32_EMULATION */
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ENTRY(xen_syscall32_target)
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ENTRY(xen_sysenter_target)
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lea 16(%rsp), %rsp /* strip %rcx, %r11 */
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mov $-ENOSYS, %rax
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pushq $0
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jmp hypercall_iret
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ENDPROC(xen_syscall32_target)
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ENDPROC(xen_sysenter_target)
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#endif /* CONFIG_IA32_EMULATION */
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