gvisor.dev/gvisor@v0.0.0-20240520182842-f9d4d51c7e0f/pkg/sentry/platform/ptrace/stub_amd64.s (about)

     1  // Copyright 2018 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  #include "funcdata.h"
    16  #include "textflag.h"
    17  
    18  #define SYS_GETPID		39
    19  #define SYS_EXIT		60
    20  #define SYS_KILL		62
    21  #define SYS_GETPPID		110
    22  #define SYS_PRCTL		157
    23  
    24  #define SIGKILL			9
    25  #define SIGSTOP			19
    26  
    27  #define PR_SET_PDEATHSIG	1
    28  
    29  // stub bootstraps the child and sends itself SIGSTOP to wait for attach.
    30  //
    31  // R15 contains the expected PPID. R15 is used instead of a more typical DI
    32  // since syscalls will clobber DI and createStub wants to pass a new PPID to
    33  // grandchildren.
    34  //
    35  // This should not be used outside the context of a new ptrace child (as the
    36  // function is otherwise a bunch of nonsense).
    37  TEXT ·stub(SB),NOSPLIT|NOFRAME,$0
    38  begin:
    39  	// N.B. This loop only executes in the context of a single-threaded
    40  	// fork child.
    41  
    42  	MOVQ $SYS_PRCTL, AX
    43  	MOVQ $PR_SET_PDEATHSIG, DI
    44  	MOVQ $SIGKILL, SI
    45  	SYSCALL
    46  
    47  	CMPQ AX, $0
    48  	JNE error
    49  
    50  	// If the parent already died before we called PR_SET_DEATHSIG then
    51  	// we'll have an unexpected PPID.
    52  	MOVQ $SYS_GETPPID, AX
    53  	SYSCALL
    54  
    55  	CMPQ AX, $0
    56  	JL error
    57  
    58  	CMPQ AX, R15
    59  	JNE parent_dead
    60  
    61  	MOVQ $SYS_GETPID, AX
    62  	SYSCALL
    63  
    64  	CMPQ AX, $0
    65  	JL error
    66  
    67  	MOVQ $0, BX
    68  
    69  	// SIGSTOP to wait for attach.
    70  	//
    71  	// The SYSCALL instruction will be used for future syscall injection by
    72  	// thread.syscall.
    73  	MOVQ AX, DI
    74  	MOVQ $SYS_KILL, AX
    75  	MOVQ $SIGSTOP, SI
    76  	SYSCALL
    77  
    78  	// The sentry sets BX to 1 when creating stub process.
    79  	CMPQ BX, $1
    80  	JE clone
    81  
    82  	// Notify the Sentry that syscall exited.
    83  done:
    84  	INT $3
    85  	// Be paranoid.
    86  	JMP done
    87  clone:
    88  	// subprocess.createStub clones a new stub process that is untraced,
    89  	// thus executing this code. We setup the PDEATHSIG before SIGSTOPing
    90  	// ourselves for attach by the tracer.
    91  	//
    92  	// R15 has been updated with the expected PPID.
    93  	CMPQ AX, $0
    94  	JE begin
    95  
    96  	// The clone syscall returns a non-zero value.
    97  	JMP done
    98  error:
    99  	// Exit with -errno.
   100  	MOVQ AX, DI
   101  	NEGQ DI
   102  	MOVQ $SYS_EXIT, AX
   103  	SYSCALL
   104  	HLT
   105  
   106  parent_dead:
   107  	MOVQ $SYS_EXIT, AX
   108  	MOVQ $1, DI
   109  	SYSCALL
   110  	HLT
   111  
   112  // func addrOfStub() uintptr
   113  TEXT ·addrOfStub(SB), $0-8
   114  	MOVQ $·stub(SB), AX
   115  	MOVQ AX, ret+0(FP)
   116  	RET
   117  
   118  // stubCall calls the stub function at the given address with the given PPID.
   119  //
   120  // This is a distinct function because stub, above, may be mapped at any
   121  // arbitrary location, and stub has a specific binary API (see above).
   122  TEXT ·stubCall(SB),NOSPLIT|NOFRAME,$0-16
   123  	MOVQ addr+0(FP), AX
   124  	MOVQ pid+8(FP), R15
   125  	JMP AX