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Jamie LiuandgVisor bot
339c9c419e
Stack expansion, GC preemption, etc. can cause an exit to host ring 3, resulting in #GP when the sentry touches the debug register. PiperOrigin-RevId: 787217537
114 lines
2.8 KiB
ArmAsm
114 lines
2.8 KiB
ArmAsm
// Copyright 2018 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "textflag.h"
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// VCPU_CPU is the location of the CPU in the vCPU struct.
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//
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// This is guaranteed to be zero.
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#define VCPU_CPU 0x0
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// ENTRY_CPU_SELF is the location of the CPU in the entry struct.
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//
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// This is sourced from ring0.
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#define ENTRY_CPU_SELF 272 // +checkoffset ring0 kernelEntry.cpuSelf
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// Context offsets.
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//
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// Only limited use of the context is done in the assembly stub below, most is
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// done in the Go handlers. However, the RIP must be examined.
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#define CONTEXT_RAX 0x90
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#define CONTEXT_RIP 0xa8
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#define CONTEXT_FP 0xe0
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// CLI is the literal byte for the disable interrupts instruction.
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//
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// This is checked as the source of the fault.
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#define CLI $0xfa
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// System call definitions.
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#define SYS_MMAP 9
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TEXT ·sigsysHandler(SB),NOSPLIT|NOFRAME,$0
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// Check if the signal is from the kernel.
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MOVQ $1, CX
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CMPL CX, 0x8(SI)
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JNE fallback
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MOVL CONTEXT_RAX(DX), CX
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CMPL CX, $SYS_MMAP
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JNE fallback
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PUSHQ DX // First argument (context).
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CALL ·seccompMmapHandler(SB) // Call the handler.
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POPQ DX // Discard the argument.
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RET
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fallback:
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// Jump to the previous signal handler.
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XORQ CX, CX
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MOVQ ·savedSigsysHandler(SB), AX
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JMP AX
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TEXT ·getcs(SB), $0-2
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MOVW CS, AX
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MOVW AX, ret+0(FP)
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RET
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TEXT ·addrOfBluepillUserHandler(SB), $0-8
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MOVQ $·bluepillUserHandler(SB), AX
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MOVQ AX, ret+0(FP)
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RET
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// func addrOfSighandler() uintptr
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TEXT ·addrOfSigsysHandler(SB), $0-8
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MOVQ $·sigsysHandler(SB), AX
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MOVQ AX, ret+0(FP)
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RET
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// dieTrampoline: see bluepill.go, bluepill_amd64_unsafe.go for documentation.
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TEXT ·dieTrampoline(SB),NOSPLIT|NOFRAME,$0
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PUSHQ BX // First argument (vCPU).
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PUSHQ AX // Fake the old RIP as caller.
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JMP ·dieHandler(SB)
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// func addrOfDieTrampoline() uintptr
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TEXT ·addrOfDieTrampoline(SB), $0-8
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MOVQ $·dieTrampoline(SB), AX
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MOVQ AX, ret+0(FP)
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RET
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TEXT ·currentCPU(SB), $0-8
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MOVQ ENTRY_CPU_SELF(GS), AX
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MOVQ AX, ret+0(FP)
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RET
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TEXT ·rdfsbase(SB), $0-8
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BYTE $0xf3; BYTE $0x48; BYTE $0x0f; BYTE $0xae; BYTE $0xc0;
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MOVQ AX, ret+0(FP)
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RET
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TEXT ·rdgsbase(SB), $0-8
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BYTE $0xf3; BYTE $0x48; BYTE $0x0f; BYTE $0xae; BYTE $0xc8;
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MOVQ AX, ret+0(FP)
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RET
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TEXT ·rdDR6(SB),NOSPLIT,$0-8
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MOVQ DR6, AX
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MOVQ AX, ret+0(FP)
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RET
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TEXT ·wrDR6(SB),NOSPLIT,$0-8
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MOVQ val+0(FP), AX
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MOVQ AX, DR6
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RET
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