syscall: restore original NOFILE rlimit in child process

If we increased the NOFILE rlimit when starting the program,
restore the original rlimit when forking a child process.

For #46279

Change-Id: Ia5d2af9ef435e5932965c15eec2e428d2130d230
Reviewed-on: https://go-review.googlesource.com/c/go/+/476097
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Bypass: Ian Lance Taylor <iant@google.com>

1 files changed, 14 insertions, 4 deletions

diff --git a/src/syscall/syscall_linux_arm64.go b/src/syscall/syscall_linux_arm64.go
index f42686262a..42984ba2ed 100644
--- a/src/syscall/syscall_linux_arm64.go
+++ b/src/syscall/syscall_linux_arm64.go
@@ -36,7 +36,7 @@ func Fstatat(fd int, path string, stat *Stat_t, flags int) error {
 //sys	sendfile(outfd int, infd int, offset *int64, count int) (written int, err error)
 //sys	Setfsgid(gid int) (err error)
 //sys	Setfsuid(uid int) (err error)
-//sysnb	setrlimit(resource int, rlim *Rlimit) (err error)
+//sysnb	setrlimit1(resource int, rlim *Rlimit) (err error)
 //sys	Shutdown(fd int, how int) (err error)
 //sys	Splice(rfd int, roff *int64, wfd int, woff *int64, len int, flags int) (n int64, err error)
 
@@ -148,13 +148,23 @@ func Getrlimit(resource int, rlim *Rlimit) error {
 	return getrlimit(resource, rlim)
 }
 
-// Setrlimit prefers the prlimit64 system call. See issue 38604.
-func Setrlimit(resource int, rlim *Rlimit) error {
+// setrlimit prefers the prlimit64 system call. See issue 38604.
+func setrlimit(resource int, rlim *Rlimit) error {
 	err := prlimit(0, resource, rlim, nil)
 	if err != ENOSYS {
 		return err
 	}
-	return setrlimit(resource, rlim)
+	return setrlimit1(resource, rlim)
+}
+
+//go:nosplit
+func rawSetrlimit(resource int, rlim *Rlimit) Errno {
+	_, _, errno := RawSyscall6(SYS_PRLIMIT64, 0, uintptr(resource), uintptr(unsafe.Pointer(rlim)), 0, 0, 0)
+	if errno != ENOSYS {
+		return errno
+	}
+	_, _, errno = RawSyscall(SYS_SETRLIMIT, uintptr(resource), uintptr(unsafe.Pointer(rlim)), 0)
+	return errno
 }
 
 func (r *PtraceRegs) PC() uint64 { return r.Pc }