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--- src/runtime/sys_freebsd_amd64.s.orig 2017-03-17 20:08:29.000000000 +0000
+++ src/runtime/sys_freebsd_amd64.s 2017-03-17 20:08:29.000000000 +0000
@@ -9,31 +9,6 @@
#include "zasm_GOOS_GOARCH.h"
#include "textflag.h"
-// FreeBSD 8, FreeBSD 9, and older versions that I have checked
-// do not restore R10 on exit from a "restarted" system call
-// if you use the SYSCALL instruction. This means that, for example,
-// if a signal arrives while the wait4 system call is executing,
-// the wait4 internally returns ERESTART, which makes the kernel
-// back up the PC to execute the SYSCALL instruction a second time.
-// However, since the kernel does not restore R10, the fourth
-// argument to the system call has been lost. (FreeBSD 9 also fails
-// to restore the fifth and sixth arguments, R8 and R9, although
-// some earlier versions did restore those correctly.)
-// The broken code is in fast_syscall in FreeBSD's amd64/amd64/exception.S.
-// It restores only DI, SI, DX, AX, and RFLAGS on system call return.
-// http://fxr.watson.org/fxr/source/amd64/amd64/exception.S?v=FREEBSD91#L399
-//
-// The INT $0x80 system call path (int0x80_syscall in FreeBSD's
-// amd64/ia32/ia32_exception.S) does not have this problem,
-// but it expects the third argument in R10. Instead of rewriting
-// all the assembly in this file, #define SYSCALL to a safe simulation
-// using INT $0x80.
-//
-// INT $0x80 is a little slower than SYSCALL, but correctness wins.
-//
-// See golang.org/issue/6372.
-#define SYSCALL MOVQ R10, CX; INT $0x80
-
TEXT runtime·sys_umtx_op(SB),NOSPLIT,$0
MOVQ addr+0(FP), DI
MOVL mode+8(FP), SI
--- src/syscall/asm_freebsd_amd64.s.orig 2017-03-17 20:20:07.000000000 +0000
+++ src/syscall/asm_freebsd_amd64.s 2017-03-17 20:20:07.000000000 +0000
@@ -12,11 +12,6 @@
// System call support for AMD64, FreeBSD
//
-// The SYSCALL variant for invoking system calls is broken in FreeBSD.
-// See comment at top of ../runtime/sys_freebsd_amd64.c and
-// golang.org/issue/6372.
-#define SYSCALL MOVQ R10, CX; INT $0x80
-
// func Syscall(trap int64, a1, a2, a3 int64) (r1, r2, err int64);
// func Syscall6(trap int64, a1, a2, a3, a4, a5, a6 int64) (r1, r2, err int64);
// func Syscall9(trap int64, a1, a2, a3, a4, a5, a6, a7, a8, a9 int64) (r1, r2, err int64)
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