From c19759aa487f7d6f479daa00e7462425f4efc481 Mon Sep 17 00:00:00 2001 From: Austin Clements Date: Tue, 13 Apr 2021 08:44:56 -0400 Subject: runtime: eliminate externalthreadhandler This function is no longer used. Eliminating this actually fixes several problems: - It made assumptions about what registers memclrNoHeapPointers would preserve. Besides being an abstraction violation and lurking maintenance issue, this actively became a problem for regabi because the call to memclrNoHeapPointers now happens through an ABI wrapper, which is generated by the compiler and hence we can't easily control what registers it clobbers. - The amd64 implementation (at least), does not interact with the host ABI correctly. Notably, it doesn't save many of the registers that are callee-save in the host ABI but caller-save in the Go ABI. - It interacts strangely with the NOSPLIT checker because it allocates an entire M and G on its stack. It worked around this on arm64, and happened to do things the NOSPLIT checker couldn't track on 386 and amd64, and happened to be *4 bytes* below the limit on arm (so any addition to the m or g structs would cause a NOSPLIT failure). See CL 309031 for a more complete explanation. Fixes #45530. Updates #40724. Change-Id: Ic70d4d7e1c17f1d796575b3377b8529449e93576 Reviewed-on: https://go-review.googlesource.com/c/go/+/309634 Trust: Austin Clements Run-TryBot: Austin Clements TryBot-Result: Go Bot Reviewed-by: Michael Pratt Reviewed-by: Michael Knyszek --- src/runtime/sys_windows_arm64.s | 60 ----------------------------------------- 1 file changed, 60 deletions(-) (limited to 'src/runtime/sys_windows_arm64.s') diff --git a/src/runtime/sys_windows_arm64.s b/src/runtime/sys_windows_arm64.s index 70f628c27d..6b28a0c2ef 100644 --- a/src/runtime/sys_windows_arm64.s +++ b/src/runtime/sys_windows_arm64.s @@ -299,66 +299,6 @@ TEXT runtime·lastcontinuetramp(SB),NOSPLIT|NOFRAME,$0 MOVD $runtime·lastcontinuehandler(SB), R1 B sigtramp<>(SB) -// externalthreadhander called with R0 = uint32 arg, R1 = Go function f. -// Need to call f(arg), which returns a uint32, and return it in R0. -TEXT runtime·externalthreadhandler(SB),NOSPLIT|TOPFRAME,$96-0 - NO_LOCAL_POINTERS - - // Push C callee-save registers R19-R28. LR, FP already saved. - SAVE_R19_TO_R28(-10*8) - - // Allocate space for args, saved R0+R1, g, and m structures. - // Hide from nosplit check. - #define extra ((64+g__size+m__size+15)&~15) - SUB $extra, RSP, R2 // hide from nosplit overflow check - MOVD R2, RSP - - // Save R0 and R1 (our args). - MOVD R0, 32(RSP) - MOVD R1, 40(RSP) - - // Zero out m and g structures. - MOVD $64(RSP), R0 - MOVD R0, 8(RSP) - MOVD $(m__size + g__size), R0 - MOVD R0, 16(RSP) - MOVD $0, 0(RSP) // not-saved LR - BL runtime·memclrNoHeapPointers(SB) - - // Initialize m and g structures. - MOVD $64(RSP), g - MOVD $g__size(g), R3 // m - MOVD R3, g_m(g) // g->m = m - MOVD g, m_g0(R3) // m->g0 = g - MOVD g, m_curg(R3) // m->curg = g - MOVD RSP, R0 - MOVD R0, g_stack+stack_hi(g) - SUB $(32*1024), R0 - MOVD R0, (g_stack+stack_lo)(g) - MOVD R0, g_stackguard0(g) - MOVD R0, g_stackguard1(g) - BL runtime·save_g(SB) - - // Call function. - MOVD 32(RSP), R0 - MOVD 40(RSP), R1 - MOVW R0, 8(RSP) - BL (R1) - - // Clear g. - MOVD $0, g - BL runtime·save_g(SB) - - // Load return value (save_g would have smashed) - MOVW (2*8)(RSP), R0 - - ADD $extra, RSP, R2 - MOVD R2, RSP - #undef extra - - RESTORE_R19_TO_R28(-10*8) - RET - GLOBL runtime·cbctxts(SB), NOPTR, $4 TEXT runtime·callbackasm1(SB),NOSPLIT,$208-0 -- cgit v1.3