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cmd/link: TestPIESize-internal is broken on openbsd/arm64 after DWARF v5 was enabled #72818

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4a6f656c opened this issue Mar 12, 2025 · 2 comments
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cmd/link: TestPIESize-internal is broken on openbsd/arm64 after DWARF v5 was enabled #72818

4a6f656c opened this issue Mar 12, 2025 · 2 comments
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BugReport Issues describing a possible bug in the Go implementation. compiler/runtime Issues related to the Go compiler and/or runtime.

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@4a6f656c
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After DWARF v5 was enabled (https://go-review.googlesource.com/c/go/+/637895), the TestPIESize-internal test fails on openbsd/arm64 with:

 --- FAIL: TestPIESize (0.02s)
    --- FAIL: TestPIESize/TestPieSize-internal (1.41s)
        elf_test.go:390: [/home/joel/src/go/bin/go build -o /tmp/TestPIESizeTestPieSize-internal2328146593/001/pie -buildmode=pie pie.go]
        elf_test.go:390: [/home/joel/src/go/bin/go build -o /tmp/TestPIESizeTestPieSize-internal2328146593/001/exe -buildmode=exe pie.go]
        elf_test.go:518: real size difference 0xe99d7, expected 0x2ce89
        elf_test.go:521: PIE unexpectedly large: got difference of 956887 (3247600 - 2292553), expected difference 183945

https://build.golang.org/log/7ebefb5b8293420696f54d3709dbb0e098b0492e

It is worth noting that running with -buildmode=pie does result in external linking being enabled - i.e. InternalLinkPIESupported("openbsd", "arm64") is false.

The program headers for the two binaries are:

$ readelf -l /tmp/exe

Elf file type is EXEC (Executable file)
Entry point 0x7cd30
There are 10 program headers, starting at offset 64

Program Headers:
  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  PHDR           0x0000000000000040 0x0000000000010040 0x0000000000010040
                 0x0000000000000230 0x0000000000000230  R      10000
  INTERP         0x0000000000000fed 0x0000000000010fed 0x0000000000010fed
                 0x0000000000000013 0x0000000000000013  R      1
      [Requesting program interpreter: /usr/libexec/ld.so]
  NOTE           0x0000000000000fd4 0x0000000000010fd4 0x0000000000010fd4
                 0x0000000000000018 0x0000000000000018  R      4
  NOTE           0x0000000000000f4c 0x0000000000010f4c 0x0000000000010f4c
                 0x0000000000000064 0x0000000000000064  R      4
  LOAD           0x0000000000000000 0x0000000000010000 0x0000000000010000
                 0x000000000009b5a0 0x000000000009b5a0  R E    10000
  LOAD           0x00000000000a0000 0x00000000000b0000 0x00000000000b0000
                 0x00000000000cb7d0 0x00000000000cb7d0  R      10000
  LOAD           0x0000000000170000 0x0000000000180000 0x0000000000180000
                 0x000000000000a5c0 0x000000000003e040  RW     10000
  DYNAMIC        0x00000000001701e0 0x00000000001801e0 0x00000000001801e0
                 0x0000000000000110 0x0000000000000110  RW     8
  TLS            0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000000000 0x0000000000000010  R      8
  OPENBSD_NOBTCF 0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000000000 0x0000000000000000    E    0

$ readelf -l /tmp/pie 
                                                         
Elf file type is DYN (Shared object file)
Entry point 0x65fa0
There are 14 program headers, starting at offset 64                                                               
                                                         
Program Headers:
  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  PHDR           0x0000000000000040 0x0000000000000040 0x0000000000000040
                 0x0000000000000310 0x0000000000000310  R      8
  INTERP         0x0000000000000350 0x0000000000000350 0x0000000000000350
                 0x0000000000000013 0x0000000000000013  R      1
      [Requesting program interpreter: /usr/libexec/ld.so]
  LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000055f98 0x0000000000055f98  R      10000
  LOAD           0x0000000000055fa0 0x0000000000065fa0 0x0000000000065fa0
                 0x000000000009bc70 0x000000000009bc70  R E    10000
  LOAD           0x00000000000f1c10 0x0000000000111c10 0x0000000000111c10
                 0x00000000000a2d20 0x00000000000a2d20  RW     10000
  LOAD           0x0000000000194930 0x00000000001c4930 0x00000000001c4930
                 0x000000000000a382 0x000000000003de70  RW     10000
  TLS            0x00000000000f1c10 0x0000000000101c10 0x0000000000101c10
                 0x0000000000000000 0x0000000000000010  R      8
  DYNAMIC        0x00000000001945d0 0x00000000001b45d0 0x00000000001b45d0
                 0x0000000000000130 0x0000000000000130  RW     8
  GNU_RELRO      0x00000000000f1c10 0x0000000000111c10 0x0000000000111c10
                 0x00000000000a2d20 0x00000000000a33f0  R      1
  GNU_EH_FRAME   0x0000000000055ae8 0x0000000000055ae8 0x0000000000055ae8
                 0x00000000000000c4 0x00000000000000c4  R      4
  OPENBSD_RANDOM 0x00000000000f1c10 0x0000000000111c10 0x0000000000111c10
                 0x0000000000000028 0x0000000000000028  RW     8
  GNU_STACK      0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000000000 0x0000000000000000  RW     0
  OPENBSD_NOBTCF 0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x0000000000000000 0x0000000000000000    E    0
  NOTE           0x0000000000000364 0x0000000000000364 0x0000000000000364
                 0x00000000000000a0 0x00000000000000a0  R      4

Seemingly this passed previously but does not now - does it make sense to compare apples with oranges^W^W^Winternally linked PIE mode with externally linked PIE mode, or should this just skip the internal test if InternalLinkPIESupported returns false?
@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Mar 12, 2025
@gopherbot
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Change https://go.dev/cl/657035 mentions this issue: cmd/link: only check PIE size difference when the linkmode is the same

@gabyhelp
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(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)

@gabyhelp gabyhelp added the BugReport Issues describing a possible bug in the Go implementation. label Mar 12, 2025
@github-project-automation github-project-automation bot moved this from Todo to Done in Go Compiler / Runtime Mar 13, 2025
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