The test for the package “./pkg/terminal” fails when using -asan or -msan.

[zhangfannie]

Please answer the following before submitting your issue:

Note: Please include any substantial examples (debug session output,
stacktraces, etc) as linked gists.

1. What version of Delve are you using (dlv version)?
   git clone https://github.com/go-delve/delve.git

2. What version of Go are you using? (go version)?
   go version devel go1.19-d9d55724bd Mon Mar 7 23:46:55 2022 +0000 linux/arm64

3. What operating system and processor architecture are you using?
   linux/arm64

4. What did you do?
   <1>. download the delve souce code.
   <2>. cd ./pkg/terminal
   <3>. go test -asan -c
   <4>. ./terminal.test

5. What did you expect to see?
   pass

6. What did you see instead?
   It reports the error as below.
   fatal error: checkptr: pointer arithmetic computed bad pointer value.
   goroutine 560 [running]:
   runtime.throw({0xd3190a?, 0x204000c98900?})
   /home/fanzha02/work/go_project/gotest/src/runtime/panic.go:992 +0x50 fp=0x204000364e90 sp=0x204000364e60 pc=0x438590
   runtime.checkptrArithmetic(0xe53b68?, {0x0?, 0x204000364f48?, 0x2?})
   /home/fanzha02/work/go_project/gotest/src/runtime/checkptr.go:52 +0xc0 fp=0x204000364ec0 sp=0x204000364e90 pc=0x409c80
   github.com/go-delve/delve/pkg/proc/native.processVmRead(0x204001042018?, 0x10, {0x204001042018?, 0x8, 0x204000364fc8?})
   /home/fanzha02/sharefolder/asanprojecttest/delve/pkg/proc/native/ptrace_linux_64bit.go:19 +0xc8 fp=0x204000364f70 sp=0x204000364ec0 pc=0x8f6ae8
   github.com/go-delve/delve/pkg/proc/native.(*nativeThread).ReadMemory(0x2040006ca790, {0x204001042018, 0x8, 0x8}, 0x10)
   /home/fanzha02/sharefolder/asanprojecttest/delve/pkg/proc/native/threads_linux.go:112 +0xc4 fp=0x204000365020 sp=0x204000364f70 pc=0x8fa514
   github.com/go-delve/delve/pkg/proc.readUintRaw({0xe55340, 0x2040006ca790}, 0x204000365128?, 0x8)
   /home/fanzha02/sharefolder/asanprojecttest/delve/pkg/proc/variables.go:1694 +0x68 fp=0x204000365080 sp=0x204000365020 pc=0x878898
   github.com/go-delve/delve/pkg/proc.getGVariable({0xe5bb80, 0x2040006ca790})
   /home/fanzha02/sharefolder/asanprojecttest/delve/pkg/proc/variables.go:445 +0x23c fp=0x204000365170 sp=0x204000365080 pc=0x86c53c

[zhangfannie]

The cause is when using -asan or -msan option, the compiler will set -d=checkptr=1 implicitly, which will instrument runtime.CheckPtrArithmetic for conversions involving unsafe.Pointer.
So the code unsafe.Pointer(addr) in line 19 of the file delve/pkg/proc/native/ptrace_linux_64bit.go is intrumented runtime.checkptrArithmetic for addr pointer, the addr is calucated by regs.TLS() + thread.BinInfo().GStructOffset() in line 445 of the file delve/pkg/proc/variables.go.

I print out the value of addr which causes the test to fail when its value is 16.

I am not familiar with the logical of these codes. can someone help with a look?Thank you.

[aarzilli]

Why is the error reported for pkg/proc/native/ptrace_linux_64bit.go:19 which is:

	p_remote := uintptr(unsafe.Pointer(&remote_iov))

and not for line 17 which contains the unsafe.Pointer conversion of addr:

	remote_iov := sys.Iovec{Base: (*byte)(unsafe.Pointer(addr)), Len: len_iov}

Anyway, this is reading memory from the target process, the value of remote_iov.Base is always wrong for delve's process, except accidentally. Would using a struct like this:

type remoteSysIovec struct {
    base uintptr
    len uint64
}

for remote_iov be better?

[zhangfannie]

@aarzilli Sorry, I added some logs to the source code that made the line numbers inconsistent. Below is the correct stack trace. And the analysis I mentioned above is correct. Thank you.

fatal error: checkptr: pointer arithmetic computed bad pointer value

goroutine 626 [running]:
runtime.throw({0xd31749?, 0x40fa00?})
/home/fanzha02/work/go_project/gotest/src/runtime/panic.go:992 +0x50 fp=0x204000362f10 sp=0x204000362ee0 pc=0x438590
runtime.checkptrArithmetic(0x3?, {0x0?, 0xffff8e9556e0?, 0x20?})
/home/fanzha02/work/go_project/gotest/src/runtime/checkptr.go:52 +0xc0 fp=0x204000362f40 sp=0x204000362f10 pc=0x409c80
github.com/go-delve/delve/pkg/proc/native.processVmRead(0x204000bfe138?, 0x8?, {0x204000bfe138?, 0x8, 0x0?})
/home/fanzha02/sharefolder/asanprojecttest/delve/pkg/proc/native/ptrace_linux_64bit.go:17 +0x58 fp=0x204000362fd0 sp=0x204000362f40 pc=0x8f6948
github.com/go-delve/delve/pkg/proc/native.(*nativeThread).ReadMemory(0x204000397ad0, {0x204000bfe138, 0x8, 0x8}, 0x10)
/home/fanzha02/sharefolder/asanprojecttest/delve/pkg/proc/native/threads_linux.go:112 +0xc4 fp=0x204000363080 sp=0x204000362fd0 pc=0x8fa374
github.com/go-delve/delve/pkg/proc.readUintRaw({0xe550a0, 0x204000397ad0}, 0x204000363168?, 0x8)
/home/fanzha02/sharefolder/asanprojecttest/delve/pkg/proc/variables.go:1690 +0x68 fp=0x2040003630e0 sp=0x204000363080 pc=0x878768
github.com/go-delve/delve/pkg/proc.getGVariable({0xe5b8e0, 0x204000397ad0})
/home/fanzha02/sharefolder/asanprojecttest/delve/pkg/proc/variables.go:441 +0x108 fp=0x204000363170 sp=0x2040003630e0 pc=0x86c408
github.com/go-delve/delve/pkg/proc.GetG({0xe5b8e0, 0x204000397ad0})
/home/fanzha02/sharefolder/asanprojecttest/delve/pkg/proc/variables.go:253 +0x4f0 fp=0x2040003631f0 sp=0x204000363170 pc=0x86b100
github.com/go-delve/delve/service/api.ConvertThread({0xe5b8e0, 0x204000397ad0})
/home/fanzha02/sharefolder/asanprojecttest/delve/service/api/conversions.go:125 +0x26c fp=0x2040003632c0 sp=0x2040003631f0 pc=0x88ba3c
github.com/go-delve/delve/service/debugger.(*Debugger).state(0x204000846e10, 0x0)
/home/fanzha02/sharefolder/asanprojecttest/delve/service/debugger/debugger.go:610 +0x764 fp=0x204000363580 sp=0x2040003632c0 pc=0x901944
github.com/go-delve/delve/service/debugger.(*Debugger).State(0x204000846e10, 0x1)
/home/fanzha02/sharefolder/asanprojecttest/delve/service/debugger/debugger.go:582 +0x3dc fp=0x204000363600 sp=0x204000363580 pc=0x90110c
github.com/go-delve/delve/service/rpc2.(*RPCServer).State(0x2040008618e0, {0x0?}, {0xffffb5975e48, 0x204001826000})
/home/fanzha02/sharefolder/asanprojecttest/delve/service/rpc2/server.go:114 +0x60 fp=0x204000363640 sp=0x204000363600 pc=0xa9e630
runtime.call32(0x204000ed2640, 0x204000992990, 0x0, 0x0, 0x0, 0x20, 0x204000363ca0)
/home/fanzha02/work/go_project/gotest/src/runtime/asm_arm64.s:508 +0x7c fp=0x204000363670 sp=0x204000363640 pc=0x469db

[aarzilli]

Ok. Should we change our use of sys.Iovec to the remoteSysIovec that uses uintptr for the Base field?

[zhangfannie]

@aarzilli I'm not a developer of the delve project. But based on the stack trace, I'm more curious why regs.TLS() + thread.BinInfo().GStructOffset() calculates a bad pointer value, 16? Thank you.

[aarzilli]

Probably because the go runtime hasn't fully finished initializing yet.