libgo: handle linking to NetBSD's versioned symbols

On NetBSD, for backwards compatibility, various libc symbols are
renamed to a symbol with a version suffix. For example, this is the
(abbreviated) definition of sigaction:

    int sigaction(...) __asm__ ("__sigaction14")

This poses a challenge for libgo, which attempts to link sigaction by
way of an "//extern" comment:

    //extern sigaction
    func sigaction(...)

This results in a reference to the deprecated compatibility symbol
"sigaction", rather than the desired "__sigaction14" symbol.

This patch introduces a new "//extern-sysinfo" comment to handle this
situation. The new mklinknames.awk script scans a package for these
comments and outputs a "//go:linkname" directive that links the wrapper
to the correct versioned symbol, as determined by parsing the __asm__
annotation on the function's declaration in gen-sysinfo.go.

For now, only the following packages are scanned by mklinknames.awk:

    os
    os/user
    runtime
    syscall

gotools/:
	* Makefile.am (check-runtime): Add runtime_linknames.go to
	--extrafiles.
	* Makefile.in: Regenerate.

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/265125

1 files changed, 58 insertions, 2 deletions

diff --git a/libgo/Makefile.am b/libgo/Makefile.am
index 26e83850435..f7a163e4a84 100644
--- a/libgo/Makefile.am
+++ b/libgo/Makefile.am
@@ -574,6 +574,48 @@ s-gccgosizes: Makefile goarch.sh
 	$(SHELL) $(srcdir)/mvifdiff.sh gccgosizes.go.tmp gccgosizes.go
 	$(STAMP) $@
 
+os_linknames.go: s-os_linknames; @true
+s-os_linknames: os-list gen-sysinfo.go $(srcdir)/mklinknames.awk $(srcdir)/go/os/*.go
+	rm -f os_linknames.go.tmp
+	$(AWK) -f $(srcdir)/mklinknames.awk -v package=os `cat os-list` > os_linknames.go.tmp
+	$(SHELL) $(srcdir)/mvifdiff.sh os_linknames.go.tmp os_linknames.go
+	$(STAMP) $@
+
+os-list: s-os-list; @true
+s-os-list: Makefile $(srcdir)/go/os/*.go
+	rm -f os-list.tmp
+	$(SHELL) $(srcdir)/match.sh --goarch=$(GOARCH) --goos=$(GOOS) --srcdir=$(srcdir)/go/os > os-list.tmp
+	$(SHELL) $(srcdir)/mvifdiff.sh os-list.tmp os-list
+	$(STAMP) $@
+
+os_user_linknames.go: s-os_user_linknames; @true
+s-os_user_linknames: os-user-list gen-sysinfo.go $(srcdir)/mklinknames.awk $(srcdir)/go/os/user/*.go
+	rm -f os_user_linknames.go.tmp
+	$(AWK) -f $(srcdir)/mklinknames.awk -v package=user `cat os-user-list` > os_user_linknames.go.tmp
+	$(SHELL) $(srcdir)/mvifdiff.sh os_user_linknames.go.tmp os_user_linknames.go
+	$(STAMP) $@
+
+os-user-list: s-os-user-list; @true
+s-os-user-list: Makefile $(srcdir)/go/os/user/*.go
+	rm -f os-user-list.tmp
+	$(SHELL) $(srcdir)/match.sh --goarch=$(GOARCH) --goos=$(GOOS) --srcdir=$(srcdir)/go/os/user > os-user-list.tmp
+	$(SHELL) $(srcdir)/mvifdiff.sh os-user-list.tmp os-user-list
+	$(STAMP) $@
+
+runtime_linknames.go: s-runtime_linknames; @true
+s-runtime_linknames: runtime-list gen-sysinfo.go $(srcdir)/mklinknames.awk $(srcdir)/go/runtime/*.go
+	rm -f runtime_linknames.go.tmp
+	$(AWK) -f $(srcdir)/mklinknames.awk -v package=runtime `cat runtime-list` > runtime_linknames.go.tmp
+	$(SHELL) $(srcdir)/mvifdiff.sh runtime_linknames.go.tmp runtime_linknames.go
+	$(STAMP) $@
+
+runtime-list: s-runtime-list; @true
+s-runtime-list: Makefile $(srcdir)/go/runtime/*.go
+	rm -f runtime-list.tmp
+	$(SHELL) $(srcdir)/match.sh --goarch=$(GOARCH) --goos=$(GOOS) --srcdir=$(srcdir)/go/runtime > runtime-list.tmp
+	$(SHELL) $(srcdir)/mvifdiff.sh runtime-list.tmp runtime-list
+	$(STAMP) $@
+
 runtime_sysinfo.go: s-runtime_sysinfo; @true
 s-runtime_sysinfo: $(srcdir)/mkrsysinfo.sh gen-sysinfo.go
 	GOARCH=$(GOARCH) GOOS=$(GOOS) $(SHELL) $(srcdir)/mkrsysinfo.sh
@@ -654,6 +696,13 @@ s-syscall_arch: Makefile
 	$(SHELL) $(srcdir)/mvifdiff.sh syscall_arch.go.tmp syscall_arch.go
 	$(STAMP) $@
 
+syscall_linknames.go: s-syscall_linknames; @true
+s-syscall_linknames: libcalls.go gen-sysinfo.go $(srcdir)/mklinknames.awk
+	rm -f syscall_linknames.go.tmp
+	$(AWK) -v package=syscall -f $(srcdir)/mklinknames.awk libcalls.go > syscall_linknames.go.tmp
+	$(SHELL) $(srcdir)/mvifdiff.sh syscall_linknames.go.tmp syscall_linknames.go
+	$(STAMP) $@
+
 SYSINFO_FLAGS = \
 	$(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) \
 	$(CPPFLAGS) $(OSCFLAGS) -O
@@ -940,8 +989,8 @@ $(foreach package,$(GOTOOL_PACKAGES),$(eval $(call PACKAGE_template,$(package)))
 math_lo_GOCFLAGS = $(MATH_FLAG)
 math_check_GOCFLAGS = $(MATH_FLAG)
 
-# Add the generated file runtime_sysinfo.go to the runtime package.
-extra_go_files_runtime = runtime_sysinfo.go sigtab.go
+# Add generated files to the runtime package.
+extra_go_files_runtime = runtime_linknames.go runtime_sysinfo.go sigtab.go
 runtime.lo.dep: $(extra_go_files_runtime)
 
 # Add generated files to the syscall package.
@@ -949,6 +998,7 @@ extra_go_files_syscall = \
 	libcalls.go \
 	sysinfo.go \
 	syscall_arch.go \
+	syscall_linknames.go \
 	$(syscall_epoll_file)
 syscall.lo.dep: $(extra_go_files_syscall)
 
@@ -1006,6 +1056,12 @@ cmd/internal/objabi.lo.dep: $(extra_go_files_cmd_internal_objabi)
 extra_go_files_cmd_go_internal_cfg = zdefaultcc.go
 cmd/go/internal/cfg.lo.dep: $(extra_go_files_cmd_go_internal_cfg)
 
+extra_go_files_os = os_linknames.go
+os.lo.dep: $(extra_go_files_os)
+
+extra_go_files_os_user = os_user_linknames.go
+os/user.lo.dep: $(extra_go_files_os_user)
+
 extra_check_libs_cmd_go_internal_cache = $(abs_builddir)/libgotool.a
 extra_check_libs_cmd_go_internal_generate = $(abs_builddir)/libgotool.a
 extra_check_libs_cmd_go_internal_get = $(abs_builddir)/libgotool.a