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runtime: eliminate externalthreadhandler

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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 <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
This commit is contained in:
Austin Clements 2021-04-13 08:44:56 -04:00
parent e69f02265c
commit c19759aa48
10 changed files with 22 additions and 261 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
src/cmd/internal/objabi/funcid.go
View File

@ -29,7 +29,6 @@ const (
FuncID_asyncPreempt
FuncID_cgocallback
FuncID_debugCallV1
FuncID_externalthreadhandler
FuncID_gcBgMarkWorker
FuncID_goexit
FuncID_gogo
@ -55,7 +54,6 @@ var funcIDs = map[string]FuncID{
"asyncPreempt": FuncID_asyncPreempt,
"cgocallback": FuncID_cgocallback,
"debugCallV1": FuncID_debugCallV1,
"externalthreadhandler": FuncID_externalthreadhandler,
"gcBgMarkWorker": FuncID_gcBgMarkWorker,
"go": FuncID_rt0_go,
"goexit": FuncID_goexit,

4
src/cmd/link/internal/ld/pe.go
View File

@ -947,9 +947,7 @@ func (f *peFile) writeOptionalHeader(ctxt *Link) {
// calls that may need more stack than we think.
//
// The default stack reserve size directly affects only the main
// thread and threads that enter in externalthreadhandler.
// For this, it must be greater than the stack size assumed by
// externalthreadhandler.
// thread.
//
// For other threads, the runtime explicitly asks the kernel
// to use the default stack size so that all stacks are

2
src/runtime/memclr_386.s
View File

@ -7,8 +7,6 @@
#include "go_asm.h"
#include "textflag.h"
// NOTE: Windows externalthreadhandler expects memclr to preserve DX.
// See memclrNoHeapPointers Go doc for important implementation constraints.
// func memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr)

2
src/runtime/memclr_amd64.s
View File

@ -7,8 +7,6 @@
#include "go_asm.h"
#include "textflag.h"
// NOTE: Windows externalthreadhandler expects memclr to preserve DX.
// See memclrNoHeapPointers Go doc for important implementation constraints.
// func memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr)

1
src/runtime/os_windows.go
View File

@ -386,7 +386,6 @@ const (
)
// in sys_windows_386.s and sys_windows_amd64.s:
func externalthreadhandler()
func getlasterror() uint32
// When loading DLLs, we prefer to use LoadLibraryEx with

1
src/runtime/symtab.go
View File

@ -317,7 +317,6 @@ const (
funcID_asyncPreempt
funcID_cgocallback
funcID_debugCallV1
funcID_externalthreadhandler
funcID_gcBgMarkWorker
funcID_goexit
funcID_gogo

51
src/runtime/sys_windows_386.s
View File

@ -156,57 +156,6 @@ TEXT runtime·lastcontinuetramp<ABIInternal>(SB),NOSPLIT,$0-0
MOVL $runtime·lastcontinuehandler(SB), AX
JMP sigtramp<>(SB)
TEXT runtime·externalthreadhandler<ABIInternal>(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<ABIInternal>(SB),NOSPLIT,$0

51
src/runtime/sys_windows_amd64.s
View File

@ -202,57 +202,6 @@ TEXT runtime·lastcontinuetramp<ABIInternal>(SB),NOSPLIT|NOFRAME,$0-0
MOVQ $runtime·lastcontinuehandler(SB), AX
JMP sigtramp<>(SB)
TEXT runtime·externalthreadhandler<ABIInternal>(SB),NOSPLIT|NOFRAME|TOPFRAME,$0
PUSHQ BP
MOVQ SP, BP
PUSHQ BX
PUSHQ SI
PUSHQ DI
PUSHQ 0x28(GS)
MOVQ SP, DX
// setup dummy m, g
SUBQ $m__size, SP // space for M
MOVQ SP, 0(SP)
MOVQ $m__size, 8(SP)
CALL runtime·memclrNoHeapPointers(SB) // smashes AX,BX,CX, maybe BP
LEAQ m_tls(SP), CX
MOVQ CX, 0x28(GS)
MOVQ SP, BX
SUBQ $g__size, SP // space for G
MOVQ SP, g(CX)
MOVQ SP, m_g0(BX)
MOVQ SP, 0(SP)
MOVQ $g__size, 8(SP)
CALL runtime·memclrNoHeapPointers(SB) // smashes AX,BX,CX, maybe BP
LEAQ g__size(SP), BX
MOVQ BX, g_m(SP)
LEAQ -32768(SP), CX // must be less than SizeOfStackReserve set by linker
MOVQ CX, (g_stack+stack_lo)(SP)
ADDQ $const__StackGuard, CX
MOVQ CX, g_stackguard0(SP)
MOVQ CX, g_stackguard1(SP)
MOVQ DX, (g_stack+stack_hi)(SP)
PUSHQ AX // room for return value
PUSHQ 32(BP) // arg for handler
CALL 16(BP)
POPQ CX
POPQ AX // pass return value to Windows in AX
get_tls(CX)
MOVQ g(CX), CX
MOVQ (g_stack+stack_hi)(CX), SP
POPQ 0x28(GS)
POPQ DI
POPQ SI
POPQ BX
POPQ BP
RET
GLOBL runtime·cbctxts(SB), NOPTR, $8
TEXT runtime·callbackasm1(SB),NOSPLIT,$0

67
src/runtime/sys_windows_arm.s
View File

@ -233,73 +233,6 @@ TEXT runtime·lastcontinuetramp<ABIInternal>(SB),NOSPLIT|NOFRAME,$0
MOVW $runtime·lastcontinuehandler(SB), R1
B sigtramp<>(SB)
// int32 externalthreadhandler(uint32 arg, int (*func)(uint32))
// stack layout:
// +----------------+
// | callee-save |
// | registers |
// +----------------+
// | m |
// +----------------+
// 20| g |
// +----------------+
// 16| func ptr (r1) |
// +----------------+
// 12| argument (r0) |
//---+----------------+
// 8 | param1 | (also return value for called Go function)
// +----------------+
// 4 | param0 |
// +----------------+
// 0 | slot for LR |
// +----------------+
//
TEXT runtime·externalthreadhandler<ABIInternal>(SB),NOSPLIT|NOFRAME|TOPFRAME,$0
MOVM.DB.W [R4-R11, R14], (R13) // push {r4-r11, lr}
SUB $(m__size + g__size + 20), R13 // space for locals
MOVW R14, 0(R13) // push LR again for anything unwinding the stack
MOVW R0, 12(R13)
MOVW R1, 16(R13)
// zero out m and g structures
ADD $20, R13, R0 // compute pointer to g
MOVW R0, 4(R13)
MOVW $(m__size + g__size), R0
MOVW R0, 8(R13)
BL runtime·memclrNoHeapPointers(SB)
// initialize m and g structures
ADD $20, R13, R2 // R2 = g
ADD $(20 + g__size), R13, R3 // R3 = m
MOVW R2, m_g0(R3) // m->g0 = g
MOVW R3, g_m(R2) // g->m = m
MOVW R2, m_curg(R3) // m->curg = g
MOVW R2, g
BL runtime·save_g(SB)
// set up stackguard stuff
MOVW R13, R0
MOVW R0, g_stack+stack_hi(g)
SUB $(32*1024), R0
MOVW R0, (g_stack+stack_lo)(g)
MOVW R0, g_stackguard0(g)
MOVW R0, g_stackguard1(g)
// move argument into position and call function
MOVW 12(R13), R0
MOVW R0, 4(R13)
MOVW 16(R13), R1
BL (R1)
// clear g
MOVW $0, g
BL runtime·save_g(SB)
MOVW 8(R13), R0 // load return value
ADD $(m__size + g__size + 20), R13 // free locals
MOVM.IA.W (R13), [R4-R11, R15] // pop {r4-r11, pc}
GLOBL runtime·cbctxts(SB), NOPTR, $4
TEXT runtime·callbackasm1<ABIInternal>(SB),NOSPLIT|NOFRAME,$0

60
src/runtime/sys_windows_arm64.s
View File

@ -299,66 +299,6 @@ TEXT runtime·lastcontinuetramp(SB),NOSPLIT|NOFRAME,$0
MOVD $runtime·lastcontinuehandler<ABIInternal>(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<ABIInternal>(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<ABIInternal>(SB),NOSPLIT,$208-0