syscall: define Syscall in terms of RawSyscall on linux

For #51087

Change-Id: I9de7e85ccf137ae73662759382334bcbe7208150
Reviewed-on: https://go-review.googlesource.com/c/go/+/388477
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

1 files changed, 22 insertions, 1 deletions

diff --git a/src/syscall/syscall_linux.go b/src/syscall/syscall_linux.go
index a9a8ecbefd..57e4769731 100644
--- a/src/syscall/syscall_linux.go
+++ b/src/syscall/syscall_linux.go
@@ -16,7 +16,6 @@ import (
 	"unsafe"
 )
 
-func Syscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno)
 func Syscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)
 
 // N.B. RawSyscall6 is provided via linkname by runtime/internal/syscall.
@@ -26,6 +25,18 @@ func Syscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)
 
 func RawSyscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)
 
+// Pull in entersyscall/exitsyscall for Syscall/Syscall6.
+//
+// Note that this can't be a push linkname because the runtime already has a
+// nameless linkname to export to assembly here and in x/sys. Additionally,
+// entersyscall fetches the caller PC and SP and thus can't have a wrapper
+// inbetween.
+
+//go:linkname runtime_entersyscall runtime.entersyscall
+func runtime_entersyscall()
+//go:linkname runtime_exitsyscall runtime.exitsyscall
+func runtime_exitsyscall()
+
 // N.B. For the Syscall functions below:
 //
 // //go:uintptrkeepalive because the uintptr argument may be converted pointers
@@ -47,6 +58,16 @@ func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno) {
 	return RawSyscall6(trap, a1, a2, a3, 0, 0, 0)
 }
 
+//go:uintptrkeepalive
+//go:nosplit
+//go:linkname Syscall
+func Syscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno) {
+	runtime_entersyscall()
+	r1, r2, err = RawSyscall(trap, a1, a2, a3)
+	runtime_exitsyscall()
+	return
+}
+
 func rawSyscallNoError(trap, a1, a2, a3 uintptr) (r1, r2 uintptr)
 
 /*