Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

cmd/link: silently performs incorrect relocations when linking foreign objects #24321

Open
infinity0 opened this issue Mar 9, 2018 · 6 comments

Comments

@infinity0
Copy link

@infinity0 infinity0 commented Mar 9, 2018

For example, when linking syso files.

Adding go:cgo_import_dynamic helps but (1) it was recently disabled for security reasons for non-cgo files, then reenabled because solaris needs it, so it's unclear if this policy will persist in the long-run for all architectures, and (2) you need to specify it for specific symbols rather than for all symbols. In any case, an error should be raised with a hint on what to do, rather than succeeding silently with invalid output.

The equivalent thing in Haskell Just Works with no extra annotations.

@andybons

This comment has been minimized.

Copy link
Member

@andybons andybons commented Mar 9, 2018

@ianlancetaylor

This comment has been minimized.

Copy link
Contributor

@ianlancetaylor ianlancetaylor commented Mar 9, 2018

Can you show us a self-contained example?

Does it work if you use -ldflags=-linkmode=external?

Perhaps we should default to external linking mode in the presence of any syso files.

@gopherbot

This comment has been minimized.

Copy link

@gopherbot gopherbot commented Apr 12, 2018

Timed out in state WaitingForInfo. Closing.

(I am just a bot, though. Please speak up if this is a mistake or you have the requested information.)

@gopherbot gopherbot closed this Apr 12, 2018
@FiloSottile

This comment has been minimized.

Copy link
Member

@FiloSottile FiloSottile commented Apr 12, 2018

Reopening, I can provide a test case from FiloSottile/ed25519-dalek-rustgo#1.

@andybons

This comment has been minimized.

Copy link
Member

@andybons andybons commented Apr 13, 2018

Removing the WaitingForInfo tag worked around GopherBot fighting you :P.

@pwaller

This comment has been minimized.

Copy link
Contributor

@pwaller pwaller commented Mar 26, 2019

@ianlancetaylor I encountered this issue while looking into #30890.

Also, whilst typing in my issue number I discovered the very next issue filed was also about relocations - interesting/amusing coincidence: #30891.

        .text
        .file   "-"
        .globl  exampleFunc      # -- Begin function exampleFunc
        .p2align        4, 0x90
        .type   exampleFunc,@function
exampleFunc:                     # @exampleFunc
.Lfunc_begin0:
        .cfi_startproc
        movzbl  .L__const.exampleFunc.one(%rip), %eax
        movl    %eax, 8(%rsp)
        retq
.Lfunc_end0:
        .size   exampleFunc, .Lfunc_end0-exampleFunc
        .cfi_endproc

        .type   .L__const.exampleFunc.one,@object # @__const.exampleFunc.one
        .section        .rodata.cst4,"aM",@progbits,4
        .p2align        2
.L__const.exampleFunc.one:
        .long   1                       # 0x1
        .size   .L__const.exampleFunc.one, 4

If I build this with as to produce a syso and go build, the relocation is missing in the resulting binary.

TEXT ·exampleFunc(SB),$0-8
  JMP exampleFunc(SB)
package main

func main() {
        println(exampleFunc())
}

func exampleFunc() uint

objdump -dr shows the relocation in the syso:

0000000000000000 <exampleFunc>:
   0:   0f b6 05 00 00 00 00    movzbl 0x0(%rip),%eax        # 7 <exampleFunc+0x7>
                        3: R_X86_64_PC32        .L__const.exampleFunc.one-0x4
   7:   89 04 24                mov    %eax,8(%rsp)
   a:   c3                      retq   

but it's missing in the go binary:

0000000000401000 <exampleFunc>:
  401000:       0f b6 05 00 00 00 00    movzbl 0x0(%rip),%eax        # 401007 <exampleFunc+0x7>
  401007:       89 04 24                mov    %eax,8(%rsp)
  40100a:       c3                      retq   
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Projects
None yet
6 participants
You can’t perform that action at this time.