syncthing: Unable to execute on WD My Cloud (armv7l)

For anyone coming here from a Google search, the problem is that firmwares from version 4 onwards use 64K pages rather than 4K. To build Go binaries for the WD My Cloud you need to apply the following patch go’s source code, then build for linux/arm.

diff --git a/src/cmd/5g/gsubr.c b/src/cmd/5g/gsubr.c
index f091979..02f6f06 100644
--- a/src/cmd/5g/gsubr.c
+++ b/src/cmd/5g/gsubr.c
@@ -36,7 +36,7 @@
 // TODO(rsc): Can make this bigger if we move
 // the text segment up higher in 5l for all GOOS.
 // At the same time, can raise StackBig in ../../runtime/stack.h.
-long unmappedzero = 4096;
+long unmappedzero = 65536;

 void
 clearp(Prog *p)
diff --git a/src/cmd/5g/peep.c b/src/cmd/5g/peep.c
index 639f4c5..6f90acd 100644
--- a/src/cmd/5g/peep.c
+++ b/src/cmd/5g/peep.c
@@ -756,7 +756,7 @@ findinc(Flow *r, Flow *r2, Adr *v)
            p = r1->prog;
            if(p->as == AADD)
            if(isdconst(&p->from))
-           if(p->from.offset > -4096 && p->from.offset < 4096)
+           if(p->from.offset > -65536 && p->from.offset < 65536)
                return r1;
        default:
            return nil;
@@ -865,7 +865,7 @@ xtramodes(Graph *g, Flow *r, Adr *a)
               (p1->from.type == D_SHIFT && (p1->from.offset&(1<<4)) == 0 &&
                ((p->as != AMOVB && p->as != AMOVBS) || (a == &p->from && (p1->from.offset&~0xf) == 0))) ||
               (p1->from.type == D_CONST &&
-               p1->from.offset > -4096 && p1->from.offset < 4096))
+               p1->from.offset > -65536 && p1->from.offset < 65536))
            if(nochange(uniqs(r1), r, p1)) {
                if(a != &p->from || v.reg != p->to.reg)
                if (finduse(g, r->s1, &v)) {
@@ -1625,5 +1625,5 @@ smallindir(Addr *a, Addr *reg)
 {
    return reg->type == D_REG && a->type == D_OREG &&
        a->reg == reg->reg &&
-       0 <= a->offset && a->offset < 4096;
+       0 <= a->offset && a->offset < 65536;
 }
diff --git a/src/cmd/5l/obj.c b/src/cmd/5l/obj.c
index c6f60ee..679a06c 100644
--- a/src/cmd/5l/obj.c
+++ b/src/cmd/5l/obj.c
@@ -91,7 +91,7 @@ archinit(void)
        if(INITDAT == -1)
            INITDAT = 0;
        if(INITRND == -1)
-           INITRND = 4096;
+           INITRND = 65536;
        break;
    case Hnacl:
        elfinit();
diff --git a/src/runtime/arch1_arm.go b/src/runtime/arch1_arm.go
index 6662eae..b2e84b8 100644
--- a/src/runtime/arch1_arm.go
+++ b/src/runtime/arch1_arm.go
@@ -9,7 +9,8 @@ const (
    _BigEndian        = 0
    _CacheLineSize    = 32
    _RuntimeGogoBytes = 60
-   _PhysPageSize     = 65536*goos_nacl + 4096*(1-goos_nacl)
-   _PCQuantum        = 4
-   _Int64Align       = 4
+   //_PhysPageSize     = 65536*goos_nacl + 4096*(1-goos_nacl)
+   _PhysPageSize = 65536
+   _PCQuantum    = 4
+   _Int64Align   = 4
 )
diff --git a/src/syscall/syscall_linux_arm.go b/src/syscall/syscall_linux_arm.go
index b127345..2f912dd 100644
--- a/src/syscall/syscall_linux_arm.go
+++ b/src/syscall/syscall_linux_arm.go
@@ -6,7 +6,7 @@ package syscall

 import "unsafe"

-func Getpagesize() int { return 4096 }
+func Getpagesize() int { return 65536 }

 func TimespecToNsec(ts Timespec) int64 { return int64(ts.Sec)*1e9 + int64(ts.Nsec) }

Note that this will break ARM builds for 4K sized pages.

I disagree, but you may ask Go devs to see if they accept contributions in this sense. I’m fairly certain that if someone offers to do the work and maintain it there’s not much reason to say no. Considering this is a free project and that there’s both a hardware and time cost (in my experience emulated system such as qemu-user didn’t work) to implement either solution, I’d not expect it to happen on its own, but only if users contribute.