runtime: fix vet complaints for all nacl

Working toward making the tree vet-safe instead of having
so many exceptions in cmd/vet/all/whitelist.

This CL makes "go vet -unsafeptr=false runtime" happy for nacl/*,
while keeping "GO_BUILDER_NAME=misc-vetall go tool dist test" happy too.

For #31916.

Change-Id: I6adb4a7b0c2b03d901fba37f9c05e74e5b7b6691
Reviewed-on: https://go-review.googlesource.com/c/go/+/176107Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/vet/all/whitelist/nacl_386.txt

-// nacl/386-specific vet whitelist. See readme.txt for details.
-
-runtime/sys_nacl_386.s: [386] nacl_clock_gettime: function nacl_clock_gettime missing Go declaration
-runtime/sys_nacl_386.s: [386] sigtramp: use of 20(SP) points beyond argument frame
-runtime/sys_nacl_386.s: [386] sigtramp: use of 4(SP) points beyond argument frame
-runtime/sys_nacl_386.s: [386] sigtramp: unknown variable ctxt
-runtime/sys_nacl_386.s: [386] sigtramp: use of 8(SP) points beyond argument frame
-runtime/sys_nacl_386.s: [386] sigtramp: use of 12(SP) points beyond argument frame
-runtime/sys_nacl_386.s: [386] sigtramp: use of 20(SP) points beyond argument frame
-runtime/sys_nacl_386.s: [386] sigtramp: unknown variable ctxt

src/cmd/vet/all/whitelist/nacl_amd64p32.txt

-// nacl/amd64p32-specific vet whitelist. See readme.txt for details.
-
-// reflect trampolines intentionally omit arg size. Same for morestack.
-runtime/asm_amd64p32.s: [amd64p32] morestack: use of 8(SP) points beyond argument frame
-runtime/asm_amd64p32.s: [amd64p32] morestack: use of 16(SP) points beyond argument frame
-runtime/asm_amd64p32.s: [amd64p32] morestack: use of 8(SP) points beyond argument frame
-
-runtime/sys_nacl_amd64p32.s: [amd64p32] sigtramp: unknown variable ctxt
-runtime/sys_nacl_amd64p32.s: [amd64p32] sigtramp: unknown variable ctxt
-runtime/sys_nacl_amd64p32.s: [amd64p32] sigtramp: unknown variable ctxt
-runtime/sys_nacl_amd64p32.s: [amd64p32] nacl_sysinfo: function nacl_sysinfo missing Go declaration
-runtime/sys_nacl_amd64p32.s: [amd64p32] nacl_clock_gettime: function nacl_clock_gettime missing Go declaration
-
-// Clearer using FP than SP, but that requires named offsets.
-runtime/asm_amd64p32.s: [amd64p32] rt0_go: unknown variable argc
-runtime/asm_amd64p32.s: [amd64p32] rt0_go: unknown variable argv
-
-runtime/asm_amd64p32.s: [amd64p32] asmcgocall: RET without writing to 4-byte ret+8(FP)

src/cmd/vet/all/whitelist/nacl_arm.txt

-// nacl/arm-specific vet whitelist. See readme.txt for details.
-
-runtime/sys_nacl_arm.s: [arm] nacl_clock_gettime: function nacl_clock_gettime missing Go declaration
-runtime/sys_nacl_arm.s: [arm] nacl_sysinfo: function nacl_sysinfo missing Go declaration

src/runtime/asm_amd64p32.s

@@ -9,9 +9,9 @@
 
 TEXT runtime·rt0_go(SB),NOSPLIT,$0
 	// copy arguments forward on an even stack
-	MOVL	argc+0(FP), AX
-	MOVL	argv+4(FP), BX
 	MOVL	SP, CX
+	MOVL	8(CX), AX	// argc
+	MOVL	12(CX), BX	// argv
 	SUBL	$128, CX		// plenty of scratch
 	ANDL	$~15, CX
 	MOVL	CX, SP
@@ -276,6 +276,7 @@ TEXT runtime·morestack(SB),NOSPLIT,$0-0
 
 	// Called from f.
 	// Set m->morebuf to f's caller.
+	NOP	SP	// tell vet SP changed - stop checking offsets
 	MOVL	8(SP), AX	// f's caller's PC
 	MOVL	AX, (m_morebuf+gobuf_pc)(BX)
 	LEAL	16(SP), AX	// f's caller's SP
@@ -443,7 +444,8 @@ TEXT runtime·jmpdefer(SB), NOSPLIT, $0-8
 // func asmcgocall(fn, arg unsafe.Pointer) int32
 // Not implemented.
 TEXT runtime·asmcgocall(SB),NOSPLIT,$0-12
-	MOVL	0, AX
+	MOVL	0, AX // crash
+	MOVL	$0, ret+8(FP) // for vet
 	RET
 
 // cgocallback(void (*fn)(void*), void *frame, uintptr framesize)

src/runtime/os_nacl.go

@@ -77,7 +77,7 @@ func mpreinit(mp *m) {
 	mp.gsignal.m = mp
 }
 
-func sigtramp()
+func sigtramp(ctxt byte)
 
 //go:nosplit
 func msigsave(mp *m) {

src/runtime/signal_nacl_amd64p32.go

@@ -6,6 +6,8 @@ package runtime
 
 import "unsafe"
 
+func nacl_sysinfo(di uint32) // cross-assembly-file call; declared for vet
+
 type sigctxt struct {
 	info *siginfo
 	ctxt unsafe.Pointer

src/runtime/sys_nacl_386.s

@@ -258,15 +258,6 @@ TEXT runtime·walltime(SB),NOSPLIT,$20
 TEXT syscall·now(SB),NOSPLIT,$0
 	JMP runtime·walltime(SB)
 
-TEXT runtime·nacl_clock_gettime(SB),NOSPLIT,$8
-	MOVL arg1+0(FP), AX
-	MOVL AX, 0(SP)
-	MOVL arg2+4(FP), AX
-	MOVL AX, 4(SP)
-	NACL_SYSCALL(SYS_clock_gettime)
-	MOVL AX, ret+8(FP)
-	RET
-
 TEXT runtime·nanotime(SB),NOSPLIT,$20
 	MOVL $0, 0(SP) // real time clock
 	LEAL 8(SP), AX
@@ -307,6 +298,7 @@ TEXT runtime·sigtramp(SB),NOSPLIT,$0
 	JMP 	ret
 
 	// save g
+	NOP	SP	// tell vet SP changed - stop checking offsets
 	MOVL	DI, 20(SP)
 
 	// g = m->gsignal
@@ -317,7 +309,7 @@ TEXT runtime·sigtramp(SB),NOSPLIT,$0
 	// copy arguments for sighandler
 	MOVL	$11, 0(SP) // signal
 	MOVL	$0, 4(SP) // siginfo
-	LEAL	ctxt+4(FP), AX
+	LEAL	8(SP), AX
 	MOVL	AX, 8(SP) // context
 	MOVL	DI, 12(SP) // g
 
@@ -359,8 +351,7 @@ ret:
 	//
 	// We smash BP, because that's what the linker smashes during RET.
 	//
-	LEAL	ctxt+4(FP), BP
-	ADDL	$64, BP
+	LEAL	72(SP), BP
 	MOVL	0(BP), AX
 	MOVL	4(BP), CX
 	MOVL	8(BP), DX

src/runtime/sys_nacl_amd64p32.s

@@ -293,13 +293,6 @@ realtime:
 TEXT syscall·now(SB),NOSPLIT,$0
 	JMP runtime·walltime(SB)
 
-TEXT runtime·nacl_clock_gettime(SB),NOSPLIT,$0
-	MOVL arg1+0(FP), DI
-	MOVL arg2+4(FP), SI
-	NACL_SYSCALL(SYS_clock_gettime)
-	MOVL AX, ret+8(FP)
-	RET
-
 TEXT runtime·nanotime(SB),NOSPLIT,$16
 	MOVQ runtime·faketime(SB), AX
 	CMPQ AX, $0

src/runtime/sys_nacl_arm.s

@@ -217,13 +217,6 @@ TEXT runtime·walltime(SB),NOSPLIT,$16
 TEXT syscall·now(SB),NOSPLIT,$0
 	B runtime·walltime(SB)
 
-TEXT runtime·nacl_clock_gettime(SB),NOSPLIT,$0
-	MOVW	arg1+0(FP), R0
-	MOVW	arg2+4(FP), R1
-	NACL_SYSCALL(SYS_clock_gettime)
-	MOVW	R0, ret+8(FP)
-	RET
-
 // int64 nanotime(void) so really
 // void nanotime(int64 *nsec)
 TEXT runtime·nanotime(SB),NOSPLIT,$16
@@ -304,9 +297,6 @@ nog:
 	MOVW	$0, R0
 	RET
 
-TEXT runtime·nacl_sysinfo(SB),NOSPLIT,$16
-	RET
-
 // func getRandomData([]byte)
 TEXT runtime·getRandomData(SB),NOSPLIT,$0-12
 	MOVW arg_base+0(FP), R0