cmd/internal/objfile: use 'B' code for ELF and PE BSS symbols For ELF check for the ELF NOBITS section type. Anything in NOBITS is a BSS symbols. For PE look for runtime.bss; for a Go program, anything runtime.bss is a BSS symbol. Fixes #77301 Change-Id: I15b9af4513a5eb0e8955014a12073c2b56bcefab Reviewed-on: https://go-review.googlesource.com/c/go/+/739080 LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: David Chase <drchase@google.com> Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com> Reviewed-by: Carlos Amedee <carlos@golang.org> Auto-Submit: Ian Lance Taylor <iant@golang.org>
diff --git a/src/cmd/internal/objfile/elf.go b/src/cmd/internal/objfile/elf.go index 6988cea..6da3190 100644 --- a/src/cmd/internal/objfile/elf.go +++ b/src/cmd/internal/objfile/elf.go
@@ -52,7 +52,11 @@ case elf.SHF_ALLOC: sym.Code = 'R' case elf.SHF_ALLOC | elf.SHF_WRITE: - sym.Code = 'D' + if sect.Type == elf.SHT_NOBITS { + sym.Code = 'B' + } else { + sym.Code = 'D' + } } } if elf.ST_BIND(s.Info) == elf.STB_LOCAL {
diff --git a/src/cmd/internal/objfile/pe.go b/src/cmd/internal/objfile/pe.go index e948212..ca8add7 100644 --- a/src/cmd/internal/objfile/pe.go +++ b/src/cmd/internal/objfile/pe.go
@@ -34,6 +34,23 @@ imageBase, _ := f.imageBase() + // When using internal linking we currently put BSS into the + // .data section. In order to set the B code correctly, + // we find the address of runtime.bss. Anything in a data section + // past runtime.bss is a BSS symbol. + // + // Just checking the section size in insufficient, + // as it will be rounded up to the page size. + // That is, there can be BSS symbols at the end of the page + // that holds the last data symbols. + var bssAddr uint32 + for _, s := range f.pe.Symbols { + if s.Name == "runtime.bss" { + bssAddr = s.Value + break + } + } + var syms []Sym for _, s := range f.pe.Symbols { const ( @@ -67,6 +84,12 @@ case ch&data != 0: if ch&permW == 0 { sym.Code = 'R' + } else if bssAddr > 0 && s.Value >= bssAddr { + // Past runtime.bss is BSS. + sym.Code = 'B' + } else if s.Value >= sect.Size { + // Past section size is BSS. + sym.Code = 'B' } else { sym.Code = 'D' }
diff --git a/src/cmd/internal/script/scripttest/setup.go b/src/cmd/internal/script/scripttest/setup.go index f9d650a..07cf8ea 100644 --- a/src/cmd/internal/script/scripttest/setup.go +++ b/src/cmd/internal/script/scripttest/setup.go
@@ -6,8 +6,10 @@ package scripttest import ( + "errors" "internal/testenv" "io" + "io/fs" "os" "path/filepath" "runtime" @@ -83,7 +85,7 @@ exename += ".exe" } toolpath := filepath.Join(testgoroot, toolsub, exename) - if err := os.Remove(toolpath); err != nil { + if err := os.Remove(toolpath); err != nil && !errors.Is(err, fs.ErrNotExist) { t.Fatalf("removing %s: %v", toolpath, err) } linkOrCopy(t, newtoolpath, toolpath)
diff --git a/src/cmd/nm/nm_test.go b/src/cmd/nm/nm_test.go index 424ac72..ce1bd7c 100644 --- a/src/cmd/nm/nm_test.go +++ b/src/cmd/nm/nm_test.go
@@ -116,6 +116,8 @@ "runtime.erodata": "R", "runtime.epclntab": "R", "runtime.noptrdata": "D", + "runtime.bss": "B", + "runtime.noptrbss": "B", } out, err = testenv.Command(t, testenv.Executable(t), exe).CombinedOutput()
diff --git a/src/cmd/nm/script_test.go b/src/cmd/nm/script_test.go new file mode 100644 index 0000000..025817d --- /dev/null +++ b/src/cmd/nm/script_test.go
@@ -0,0 +1,35 @@ +// Copyright 2026 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package main + +import ( + "cmd/internal/script/scripttest" + "flag" + "internal/testenv" + "os" + "testing" +) + +//go:generate go test cmd/nm -v -run=TestScript/README --fixreadme + +var fixReadme = flag.Bool("fixreadme", false, "if true, update README for script tests") + +func TestScript(t *testing.T) { + testenv.MustHaveGoBuild(t) + + testExe, testExeErr := os.Executable() + + repls := []scripttest.ToolReplacement{} + if testExeErr == nil { + repls = []scripttest.ToolReplacement{ + scripttest.ToolReplacement{ + ToolName: "nm", + ReplacementPath: testExe, + EnvVar: "GO_NMTEST_IS_NM=1", + }, + } + } + scripttest.RunToolScriptTest(t, repls, "testdata/script", *fixReadme) +}
diff --git a/src/cmd/nm/testdata/script/README b/src/cmd/nm/testdata/script/README new file mode 100644 index 0000000..9ec997a --- /dev/null +++ b/src/cmd/nm/testdata/script/README
@@ -0,0 +1,286 @@ +This file is generated by 'go generate'. DO NOT EDIT. + +This directory holds test scripts *.txt run during 'go test cmd/<toolname>'. +To run a specific script foo.txt + + go test cmd/<toolname> -run=Script/^foo$ + +In general script files should have short names: a few words, + not whole sentences. +The first word should be the general category of behavior being tested, +often the name of a go subcommand (build, link, compile, ...) or concept (vendor, pattern). + +Each script is a text archive (go doc internal/txtar). +The script begins with an actual command script to run +followed by the content of zero or more supporting files to +create in the script's temporary file system before it starts executing. + +As an example, run_hello.txt says: + + # hello world + go run hello.go + stderr 'hello world' + ! stdout . + + -- hello.go -- + package main + func main() { println("hello world") } + +Each script runs in a fresh temporary work directory tree, available to scripts as $WORK. +Scripts also have access to other environment variables, including: + + GOARCH=<target GOARCH> + GOOS=<target GOOS> + TMPDIR=$WORK/tmp + devnull=<value of os.DevNull> + goversion=<current Go version; for example, 1.12> + +On Plan 9, the variables $path and $home are set instead of $PATH and $HOME. +On Windows, the variables $USERPROFILE and $TMP are set instead of +$HOME and $TMPDIR. + +The lines at the top of the script are a sequence of commands to be executed by +a small script engine configured in .../cmd/internal/script/scripttest/run.go (not the system shell). + +Each line of a script is parsed into a sequence of space-separated command +words, with environment variable expansion within each word and # marking +an end-of-line comment. Additional variables named ':' and '/' are expanded +within script arguments (expanding to the value of os.PathListSeparator and +os.PathSeparator respectively) but are not inherited in subprocess environments. + +Adding single quotes around text keeps spaces in that text from being treated +as word separators and also disables environment variable expansion. Inside a +single-quoted block of text, a repeated single quote indicates a literal single +quote, as in: + + 'Don''t communicate by sharing memory.' + +A line beginning with # is a comment and conventionally explains what is being +done or tested at the start of a new section of the script. + +Commands are executed one at a time, and errors are checked for each command; +if any command fails unexpectedly, no subsequent commands in the script are +executed. The command prefix ! indicates that the command on the rest of the +line (typically go or a matching predicate) must fail instead of succeeding. +The command prefix ? indicates that the command may or may not succeed, but the +script should continue regardless. + +The command prefix [cond] indicates that the command on the rest of the line +should only run when the condition is satisfied. + +A condition can be negated: [!root] means to run the rest of the line only if +the user is not root. Multiple conditions may be given for a single command, +for example, '[linux] [amd64] skip'. The command will run if all conditions are +satisfied. + +When TestScript runs a script and the script fails, by default TestScript shows +the execution of the most recent phase of the script (since the last # comment) +and only shows the # comments for earlier phases. + +Note also that in reported output, the actual name of the per-script temporary directory +has been consistently replaced with the literal string $WORK. + +The available commands are: +cat files... + concatenate files and print to the script's stdout buffer + + +cc args... + run the platform C compiler + + +cd dir + change the working directory + + +chmod perm paths... + change file mode bits + + Changes the permissions of the named files or directories to + be equal to perm. + Only numerical permissions are supported. + +cmp [-q] file1 file2 + compare files for differences + + By convention, file1 is the actual data and file2 is the + expected data. + The command succeeds if the file contents are identical. + File1 can be 'stdout' or 'stderr' to compare the stdout or + stderr buffer from the most recent command. + +cmpenv [-q] file1 file2 + compare files for differences, with environment expansion + + By convention, file1 is the actual data and file2 is the + expected data. + The command succeeds if the file contents are identical + after substituting variables from the script environment. + File1 can be 'stdout' or 'stderr' to compare the script's + stdout or stderr buffer. + +cp src... dst + copy files to a target file or directory + + src can include 'stdout' or 'stderr' to copy from the + script's stdout or stderr buffer. + +echo string... + display a line of text + + +env [key[=value]...] + set or log the values of environment variables + + With no arguments, print the script environment to the log. + Otherwise, add the listed key=value pairs to the environment + or print the listed keys. + +exec program [args...] [&] + run an executable program with arguments + + Note that 'exec' does not terminate the script (unlike Unix + shells). + +exists [-readonly] [-exec] file... + check that files exist + + +go [args...] [&] + run the 'go' program provided by the script host + + +grep [-count=N] [-q] 'pattern' file + find lines in a file that match a pattern + + The command succeeds if at least one match (or the exact + count, if given) is found. + The -q flag suppresses printing of matches. + +help [-v] name... + log help text for commands and conditions + + To display help for a specific condition, enclose it in + brackets: 'help [amd64]'. + To display complete documentation when listing all commands, + pass the -v flag. + +mkdir path... + create directories, if they do not already exist + + Unlike Unix mkdir, parent directories are always created if + needed. + +mv old new + rename a file or directory to a new path + + OS-specific restrictions may apply when old and new are in + different directories. + +replace [old new]... file + replace strings in a file + + The 'old' and 'new' arguments are unquoted as if in quoted + Go strings. + +rm path... + remove a file or directory + + If the path is a directory, its contents are removed + recursively. + +skip [msg] + skip the current test + + +sleep duration [&] + sleep for a specified duration + + The duration must be given as a Go time.Duration string. + +stderr [-count=N] [-q] 'pattern' file + find lines in the stderr buffer that match a pattern + + The command succeeds if at least one match (or the exact + count, if given) is found. + The -q flag suppresses printing of matches. + +stdout [-count=N] [-q] 'pattern' file + find lines in the stdout buffer that match a pattern + + The command succeeds if at least one match (or the exact + count, if given) is found. + The -q flag suppresses printing of matches. + +stop [msg] + stop execution of the script + + The message is written to the script log, but no error is + reported from the script engine. + +symlink path -> target + create a symlink + + Creates path as a symlink to target. + The '->' token (like in 'ls -l' output on Unix) is required. + +wait + wait for completion of background commands + + Waits for all background commands to complete. + The output (and any error) from each command is printed to + the log in the order in which the commands were started. + After the call to 'wait', the script's stdout and stderr + buffers contain the concatenation of the background + commands' outputs. + + + +The available conditions are: +[GOARCH:*] + runtime.GOARCH == <suffix> +[GODEBUG:*] + GODEBUG contains <suffix> +[GOEXPERIMENT:*] + GOEXPERIMENT <suffix> is enabled +[GOOS:*] + runtime.GOOS == <suffix> +[asan] + GOOS/GOARCH supports -asan +[buildmode:*] + go supports -buildmode=<suffix> +[cgo] + host CGO_ENABLED +[cgolinkext] + platform requires external linking for cgo +[compiler:*] + runtime.Compiler == <suffix> +[cross] + cmd/go GOOS/GOARCH != GOHOSTOS/GOHOSTARCH +[exec:*] + <suffix> names an executable in the test binary's PATH +[fuzz] + GOOS/GOARCH supports -fuzz +[fuzz-instrumented] + GOOS/GOARCH supports -fuzz with instrumentation +[go-builder] + GO_BUILDER_NAME is non-empty +[link] + testenv.HasLink() +[msan] + GOOS/GOARCH supports -msan +[mustlinkext] + platform always requires external linking +[pielinkext] + platform requires external linking for PIE +[race] + GOOS/GOARCH supports -race +[root] + os.Geteuid() == 0 +[short] + testing.Short() +[symlink] + testenv.HasSymlink() +[verbose] + testing.Verbose() +
diff --git a/src/cmd/nm/testdata/script/issue77301.txt b/src/cmd/nm/testdata/script/issue77301.txt new file mode 100644 index 0000000..aa0c9c6 --- /dev/null +++ b/src/cmd/nm/testdata/script/issue77301.txt
@@ -0,0 +1,20 @@ +# Tests the correct symbol placement for initialized vs uninitialized +# globals in the respective sections: https://go.dev/issues/77301 +go build -o main +exec go tool nm main +stdout 'B main.globalUninitialized' +stdout 'D main.globalInitialized' + +-- go.mod -- +module nm_bss_symbol_check + +-- main.go -- +package main + +var globalUninitialized int64 +var globalInitialized int64 = 42 + +func main() { + println(globalUninitialized) + println(globalInitialized) +}