82 lines
3.1 KiB
Go
82 lines
3.1 KiB
Go
// Copyright 2020 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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// +build arm64
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package arch
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const restartSyscallNr = uintptr(128)
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// SyscallSaveOrig save the value of the register R0 which is clobbered in
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// syscall handler(doSyscall()).
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//
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// In linux, at the entry of the syscall handler(el0_svc_common()), value of R0
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// is saved to the pt_regs.orig_x0 in kernel code. But currently, the orig_x0
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// was not accessible to the user space application, so we have to do the same
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// operation in the sentry code to save the R0 value into the App context.
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func (c *context64) SyscallSaveOrig() {
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c.OrigR0 = c.Regs.Regs[0]
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}
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// SyscallNo returns the syscall number according to the 64-bit convention.
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func (c *context64) SyscallNo() uintptr {
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return uintptr(c.Regs.Regs[8])
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}
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// SyscallArgs provides syscall arguments according to the 64-bit convention.
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//
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// Due to the way addresses are mapped for the sentry this binary *must* be
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// built in 64-bit mode. So we can just assume the syscall numbers that come
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// back match the expected host system call numbers.
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// General purpose registers usage on Arm64:
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// R0...R7: parameter/result registers.
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// R8: indirect result location register.
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// R9...R15: temporary registers.
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// R16: the first intra-procedure-call scratch register.
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// R17: the second intra-procedure-call scratch register.
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// R18: the platform register.
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// R19...R28: callee-saved registers.
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// R29: the frame pointer.
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// R30: the link register.
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func (c *context64) SyscallArgs() SyscallArguments {
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return SyscallArguments{
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SyscallArgument{Value: uintptr(c.OrigR0)},
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SyscallArgument{Value: uintptr(c.Regs.Regs[1])},
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SyscallArgument{Value: uintptr(c.Regs.Regs[2])},
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SyscallArgument{Value: uintptr(c.Regs.Regs[3])},
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SyscallArgument{Value: uintptr(c.Regs.Regs[4])},
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SyscallArgument{Value: uintptr(c.Regs.Regs[5])},
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}
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}
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// RestartSyscall implements Context.RestartSyscall.
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// Prepare for system call restart, OrigR0 will be restored to R0.
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// Please see the linux code as reference:
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// arch/arm64/kernel/signal.c:do_signal()
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func (c *context64) RestartSyscall() {
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c.Regs.Pc -= SyscallWidth
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// R0 will be backed up into OrigR0 when entering doSyscall().
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// Please see the linux code as reference:
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// arch/arm64/kernel/syscall.c:el0_svc_common().
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// Here we restore it back.
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c.Regs.Regs[0] = uint64(c.OrigR0)
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}
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// RestartSyscallWithRestartBlock implements Context.RestartSyscallWithRestartBlock.
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func (c *context64) RestartSyscallWithRestartBlock() {
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c.Regs.Pc -= SyscallWidth
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c.Regs.Regs[0] = uint64(c.OrigR0)
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c.Regs.Regs[8] = uint64(restartSyscallNr)
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}
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