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_386.s | 51 ------------------------------------------- 1 file changed, 51 deletions(-) (limited to 'src/runtime/sys_windows_386.s') diff --git a/src/runtime/sys_windows_386.s b/src/runtime/sys_windows_386.s index c8839b9976..d6b521ab65 100644 --- a/src/runtime/sys_windows_386.s +++ b/src/runtime/sys_windows_386.s @@ -156,57 +156,6 @@ TEXT runtime·lastcontinuetramp(SB),NOSPLIT,$0-0 MOVL $runtime·lastcontinuehandler(SB), AX JMP sigtramp<>(SB) -TEXT runtime·externalthreadhandler(SB),NOSPLIT|TOPFRAME,$0 - PUSHL BP - MOVL SP, BP - PUSHL BX - PUSHL SI - PUSHL DI - PUSHL 0x14(FS) - MOVL SP, DX - - // setup dummy m, g - SUBL $m__size, SP // space for M - MOVL SP, 0(SP) - MOVL $m__size, 4(SP) - CALL runtime·memclrNoHeapPointers(SB) // smashes AX,BX,CX - - LEAL m_tls(SP), CX - MOVL CX, 0x14(FS) - MOVL SP, BX - SUBL $g__size, SP // space for G - MOVL SP, g(CX) - MOVL SP, m_g0(BX) - - MOVL SP, 0(SP) - MOVL $g__size, 4(SP) - CALL runtime·memclrNoHeapPointers(SB) // smashes AX,BX,CX - LEAL g__size(SP), BX - MOVL BX, g_m(SP) - - LEAL -32768(SP), CX // must be less than SizeOfStackReserve set by linker - MOVL CX, (g_stack+stack_lo)(SP) - ADDL $const__StackGuard, CX - MOVL CX, g_stackguard0(SP) - MOVL CX, g_stackguard1(SP) - MOVL DX, (g_stack+stack_hi)(SP) - - PUSHL AX // room for return value - PUSHL 16(BP) // arg for handler - CALL 8(BP) - POPL CX - POPL AX // pass return value to Windows in AX - - get_tls(CX) - MOVL g(CX), CX - MOVL (g_stack+stack_hi)(CX), SP - POPL 0x14(FS) - POPL DI - POPL SI - POPL BX - POPL BP - RET - GLOBL runtime·cbctxts(SB), NOPTR, $4 TEXT runtime·callbackasm1(SB),NOSPLIT,$0 -- cgit v1.3