summaryrefslogtreecommitdiffstats
path: root/src/runtime/sys_windows_arm.s
diff options
context:
space:
mode:
Diffstat (limited to 'src/runtime/sys_windows_arm.s')
-rw-r--r--src/runtime/sys_windows_arm.s694
1 files changed, 694 insertions, 0 deletions
diff --git a/src/runtime/sys_windows_arm.s b/src/runtime/sys_windows_arm.s
new file mode 100644
index 0000000..fe26708
--- /dev/null
+++ b/src/runtime/sys_windows_arm.s
@@ -0,0 +1,694 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "go_asm.h"
+#include "go_tls.h"
+#include "textflag.h"
+
+// void runtime·asmstdcall(void *c);
+TEXT runtime·asmstdcall(SB),NOSPLIT|NOFRAME,$0
+ MOVM.DB.W [R4, R5, R14], (R13) // push {r4, r5, lr}
+ MOVW R0, R4 // put libcall * in r4
+ MOVW R13, R5 // save stack pointer in r5
+
+ // SetLastError(0)
+ MOVW $0, R0
+ MRC 15, 0, R1, C13, C0, 2
+ MOVW R0, 0x34(R1)
+
+ MOVW 8(R4), R12 // libcall->args
+
+ // Do we have more than 4 arguments?
+ MOVW 4(R4), R0 // libcall->n
+ SUB.S $4, R0, R2
+ BLE loadregs
+
+ // Reserve stack space for remaining args
+ SUB R2<<2, R13
+ BIC $0x7, R13 // alignment for ABI
+
+ // R0: count of arguments
+ // R1:
+ // R2: loop counter, from 0 to (n-4)
+ // R3: scratch
+ // R4: pointer to libcall struct
+ // R12: libcall->args
+ MOVW $0, R2
+stackargs:
+ ADD $4, R2, R3 // r3 = args[4 + i]
+ MOVW R3<<2(R12), R3
+ MOVW R3, R2<<2(R13) // stack[i] = r3
+
+ ADD $1, R2 // i++
+ SUB $4, R0, R3 // while (i < (n - 4))
+ CMP R3, R2
+ BLT stackargs
+
+loadregs:
+ CMP $3, R0
+ MOVW.GT 12(R12), R3
+
+ CMP $2, R0
+ MOVW.GT 8(R12), R2
+
+ CMP $1, R0
+ MOVW.GT 4(R12), R1
+
+ CMP $0, R0
+ MOVW.GT 0(R12), R0
+
+ BIC $0x7, R13 // alignment for ABI
+ MOVW 0(R4), R12 // branch to libcall->fn
+ BL (R12)
+
+ MOVW R5, R13 // free stack space
+ MOVW R0, 12(R4) // save return value to libcall->r1
+ MOVW R1, 16(R4)
+
+ // GetLastError
+ MRC 15, 0, R1, C13, C0, 2
+ MOVW 0x34(R1), R0
+ MOVW R0, 20(R4) // store in libcall->err
+
+ MOVM.IA.W (R13), [R4, R5, R15]
+
+TEXT runtime·badsignal2(SB),NOSPLIT|NOFRAME,$0
+ MOVM.DB.W [R4, R14], (R13) // push {r4, lr}
+ MOVW R13, R4 // save original stack pointer
+ SUB $8, R13 // space for 2 variables
+ BIC $0x7, R13 // alignment for ABI
+
+ // stderr
+ MOVW runtime·_GetStdHandle(SB), R1
+ MOVW $-12, R0
+ BL (R1)
+
+ MOVW $runtime·badsignalmsg(SB), R1 // lpBuffer
+ MOVW $runtime·badsignallen(SB), R2 // lpNumberOfBytesToWrite
+ MOVW (R2), R2
+ ADD $0x4, R13, R3 // lpNumberOfBytesWritten
+ MOVW $0, R12 // lpOverlapped
+ MOVW R12, (R13)
+
+ MOVW runtime·_WriteFile(SB), R12
+ BL (R12)
+
+ MOVW R4, R13 // restore SP
+ MOVM.IA.W (R13), [R4, R15] // pop {r4, pc}
+
+TEXT runtime·getlasterror(SB),NOSPLIT,$0
+ MRC 15, 0, R0, C13, C0, 2
+ MOVW 0x34(R0), R0
+ MOVW R0, ret+0(FP)
+ RET
+
+TEXT runtime·setlasterror(SB),NOSPLIT|NOFRAME,$0
+ MRC 15, 0, R1, C13, C0, 2
+ MOVW R0, 0x34(R1)
+ RET
+
+// Called by Windows as a Vectored Exception Handler (VEH).
+// First argument is pointer to struct containing
+// exception record and context pointers.
+// Handler function is stored in R1
+// Return 0 for 'not handled', -1 for handled.
+// int32_t sigtramp(
+// PEXCEPTION_POINTERS ExceptionInfo,
+// func *GoExceptionHandler);
+TEXT sigtramp<>(SB),NOSPLIT|NOFRAME,$0
+ MOVM.DB.W [R0, R4-R11, R14], (R13) // push {r0, r4-r11, lr} (SP-=40)
+ SUB $(8+20), R13 // reserve space for g, sp, and
+ // parameters/retval to go call
+
+ MOVW R0, R6 // Save param0
+ MOVW R1, R7 // Save param1
+
+ BL runtime·load_g(SB)
+ CMP $0, g // is there a current g?
+ BL.EQ runtime·badsignal2(SB)
+
+ // save g and SP in case of stack switch
+ MOVW R13, 24(R13)
+ MOVW g, 20(R13)
+
+ // do we need to switch to the g0 stack?
+ MOVW g, R5 // R5 = g
+ MOVW g_m(R5), R2 // R2 = m
+ MOVW m_g0(R2), R4 // R4 = g0
+ CMP R5, R4 // if curg == g0
+ BEQ g0
+
+ // switch to g0 stack
+ MOVW R4, g // g = g0
+ MOVW (g_sched+gobuf_sp)(g), R3 // R3 = g->gobuf.sp
+ BL runtime·save_g(SB)
+
+ // traceback will think that we've done PUSH and SUB
+ // on this stack, so subtract them here to match.
+ // (we need room for sighandler arguments anyway).
+ // and re-save old SP for restoring later.
+ SUB $(40+8+20), R3
+ MOVW R13, 24(R3) // save old stack pointer
+ MOVW R3, R13 // switch stack
+
+g0:
+ MOVW 0(R6), R2 // R2 = ExceptionPointers->ExceptionRecord
+ MOVW 4(R6), R3 // R3 = ExceptionPointers->ContextRecord
+
+ // make it look like mstart called us on g0, to stop traceback
+ MOVW $runtime·mstart(SB), R4
+
+ MOVW R4, 0(R13) // Save link register for traceback
+ MOVW R2, 4(R13) // Move arg0 (ExceptionRecord) into position
+ MOVW R3, 8(R13) // Move arg1 (ContextRecord) into position
+ MOVW R5, 12(R13) // Move arg2 (original g) into position
+ BL (R7) // Call the go routine
+ MOVW 16(R13), R4 // Fetch return value from stack
+
+ // Compute the value of the g0 stack pointer after deallocating
+ // this frame, then allocating 8 bytes. We may need to store
+ // the resume SP and PC on the g0 stack to work around
+ // control flow guard when we resume from the exception.
+ ADD $(40+20), R13, R12
+
+ // switch back to original stack and g
+ MOVW 24(R13), R13
+ MOVW 20(R13), g
+ BL runtime·save_g(SB)
+
+done:
+ MOVW R4, R0 // move retval into position
+ ADD $(8 + 20), R13 // free locals
+ MOVM.IA.W (R13), [R3, R4-R11, R14] // pop {r3, r4-r11, lr}
+
+ // if return value is CONTINUE_SEARCH, do not set up control
+ // flow guard workaround
+ CMP $0, R0
+ BEQ return
+
+ // Check if we need to set up the control flow guard workaround.
+ // On Windows/ARM, the stack pointer must lie within system
+ // stack limits when we resume from exception.
+ // Store the resume SP and PC on the g0 stack,
+ // and return to returntramp on the g0 stack. returntramp
+ // pops the saved PC and SP from the g0 stack, resuming execution
+ // at the desired location.
+ // If returntramp has already been set up by a previous exception
+ // handler, don't clobber the stored SP and PC on the stack.
+ MOVW 4(R3), R3 // PEXCEPTION_POINTERS->Context
+ MOVW 0x40(R3), R2 // load PC from context record
+ MOVW $returntramp<>(SB), R1
+ CMP R1, R2
+ B.EQ return // do not clobber saved SP/PC
+
+ // Save resume SP and PC on g0 stack
+ MOVW 0x38(R3), R2 // load SP from context record
+ MOVW R2, 0(R12) // Store resume SP on g0 stack
+ MOVW 0x40(R3), R2 // load PC from context record
+ MOVW R2, 4(R12) // Store resume PC on g0 stack
+
+ // Set up context record to return to returntramp on g0 stack
+ MOVW R12, 0x38(R3) // save g0 stack pointer
+ // in context record
+ MOVW $returntramp<>(SB), R2 // save resume address
+ MOVW R2, 0x40(R3) // in context record
+
+return:
+ B (R14) // return
+
+//
+// Trampoline to resume execution from exception handler.
+// This is part of the control flow guard workaround.
+// It switches stacks and jumps to the continuation address.
+//
+TEXT returntramp<>(SB),NOSPLIT|NOFRAME,$0
+ MOVM.IA (R13), [R13, R15] // ldm sp, [sp, pc]
+
+TEXT runtime·exceptiontramp(SB),NOSPLIT|NOFRAME,$0
+ MOVW $runtime·exceptionhandler(SB), R1
+ B sigtramp<>(SB)
+
+TEXT runtime·firstcontinuetramp(SB),NOSPLIT|NOFRAME,$0
+ MOVW $runtime·firstcontinuehandler(SB), R1
+ B sigtramp<>(SB)
+
+TEXT runtime·lastcontinuetramp(SB),NOSPLIT|NOFRAME,$0
+ MOVW $runtime·lastcontinuehandler(SB), R1
+ B sigtramp<>(SB)
+
+TEXT runtime·ctrlhandler(SB),NOSPLIT|NOFRAME,$0
+ MOVW $runtime·ctrlhandler1(SB), R1
+ B runtime·externalthreadhandler(SB)
+
+TEXT runtime·profileloop(SB),NOSPLIT|NOFRAME,$0
+ MOVW $runtime·profileloop1(SB), R1
+ B runtime·externalthreadhandler(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 |
+// +----------------+
+// 4 | param0 |
+// +----------------+
+// 0 | retval |
+// +----------------+
+//
+TEXT runtime·externalthreadhandler(SB),NOSPLIT|NOFRAME,$0
+ MOVM.DB.W [R4-R11, R14], (R13) // push {r4-r11, lr}
+ SUB $(m__size + g__size + 20), R13 // space for locals
+ 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 0(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(SB),NOSPLIT|NOFRAME,$0
+ // On entry, the trampoline in zcallback_windows_arm.s left
+ // the callback index in R12 (which is volatile in the C ABI).
+
+ // Push callback register arguments r0-r3. We do this first so
+ // they're contiguous with stack arguments.
+ MOVM.DB.W [R0-R3], (R13)
+ // Push C callee-save registers r4-r11 and lr.
+ MOVM.DB.W [R4-R11, R14], (R13)
+ SUB $(16 + callbackArgs__size), R13 // space for locals
+
+ // Create a struct callbackArgs on our stack.
+ MOVW R12, (16+callbackArgs_index)(R13) // callback index
+ MOVW $(16+callbackArgs__size+4*9)(R13), R0
+ MOVW R0, (16+callbackArgs_args)(R13) // address of args vector
+ MOVW $0, R0
+ MOVW R0, (16+callbackArgs_result)(R13) // result
+
+ // Prepare for entry to Go.
+ BL runtime·load_g(SB)
+
+ // Call cgocallback, which will call callbackWrap(frame).
+ MOVW $0, R0
+ MOVW R0, 12(R13) // context
+ MOVW $16(R13), R1 // R1 = &callbackArgs{...}
+ MOVW R1, 8(R13) // frame (address of callbackArgs)
+ MOVW $·callbackWrap(SB), R1
+ MOVW R1, 4(R13) // PC of function to call
+ BL runtime·cgocallback(SB)
+
+ // Get callback result.
+ MOVW (16+callbackArgs_result)(R13), R0
+
+ ADD $(16 + callbackArgs__size), R13 // free locals
+ MOVM.IA.W (R13), [R4-R11, R12] // pop {r4-r11, lr=>r12}
+ ADD $(4*4), R13 // skip r0-r3
+ B (R12) // return
+
+// uint32 tstart_stdcall(M *newm);
+TEXT runtime·tstart_stdcall(SB),NOSPLIT|NOFRAME,$0
+ MOVM.DB.W [R4-R11, R14], (R13) // push {r4-r11, lr}
+
+ MOVW m_g0(R0), g
+ MOVW R0, g_m(g)
+ BL runtime·save_g(SB)
+
+ // do per-thread TLS initialization
+ BL init_thread_tls<>(SB)
+
+ // Layout new m scheduler stack on os stack.
+ MOVW R13, R0
+ MOVW R0, g_stack+stack_hi(g)
+ SUB $(64*1024), R0
+ MOVW R0, (g_stack+stack_lo)(g)
+ MOVW R0, g_stackguard0(g)
+ MOVW R0, g_stackguard1(g)
+
+ BL runtime·emptyfunc(SB) // fault if stack check is wrong
+ BL runtime·mstart(SB)
+
+ // Exit the thread.
+ MOVW $0, R0
+ MOVM.IA.W (R13), [R4-R11, R15] // pop {r4-r11, pc}
+
+// onosstack calls fn on OS stack.
+// adapted from asm_arm.s : systemstack
+// func onosstack(fn unsafe.Pointer, arg uint32)
+TEXT runtime·onosstack(SB),NOSPLIT,$0
+ MOVW fn+0(FP), R5 // R5 = fn
+ MOVW arg+4(FP), R6 // R6 = arg
+
+ // This function can be called when there is no g,
+ // for example, when we are handling a callback on a non-go thread.
+ // In this case we're already on the system stack.
+ CMP $0, g
+ BEQ noswitch
+
+ MOVW g_m(g), R1 // R1 = m
+
+ MOVW m_gsignal(R1), R2 // R2 = gsignal
+ CMP g, R2
+ B.EQ noswitch
+
+ MOVW m_g0(R1), R2 // R2 = g0
+ CMP g, R2
+ B.EQ noswitch
+
+ MOVW m_curg(R1), R3
+ CMP g, R3
+ B.EQ switch
+
+ // Bad: g is not gsignal, not g0, not curg. What is it?
+ // Hide call from linker nosplit analysis.
+ MOVW $runtime·badsystemstack(SB), R0
+ BL (R0)
+ B runtime·abort(SB)
+
+switch:
+ // save our state in g->sched. Pretend to
+ // be systemstack_switch if the G stack is scanned.
+ MOVW $runtime·systemstack_switch(SB), R3
+ ADD $4, R3, R3 // get past push {lr}
+ MOVW R3, (g_sched+gobuf_pc)(g)
+ MOVW R13, (g_sched+gobuf_sp)(g)
+ MOVW LR, (g_sched+gobuf_lr)(g)
+ MOVW g, (g_sched+gobuf_g)(g)
+
+ // switch to g0
+ MOVW R2, g
+ MOVW (g_sched+gobuf_sp)(R2), R3
+ // make it look like mstart called systemstack on g0, to stop traceback
+ SUB $4, R3, R3
+ MOVW $runtime·mstart(SB), R4
+ MOVW R4, 0(R3)
+ MOVW R3, R13
+
+ // call target function
+ MOVW R6, R0 // arg
+ BL (R5)
+
+ // switch back to g
+ MOVW g_m(g), R1
+ MOVW m_curg(R1), g
+ MOVW (g_sched+gobuf_sp)(g), R13
+ MOVW $0, R3
+ MOVW R3, (g_sched+gobuf_sp)(g)
+ RET
+
+noswitch:
+ // Using a tail call here cleans up tracebacks since we won't stop
+ // at an intermediate systemstack.
+ MOVW.P 4(R13), R14 // restore LR
+ MOVW R6, R0 // arg
+ B (R5)
+
+// Runs on OS stack. Duration (in 100ns units) is in R0.
+TEXT runtime·usleep2(SB),NOSPLIT|NOFRAME,$0
+ MOVM.DB.W [R4, R14], (R13) // push {r4, lr}
+ MOVW R13, R4 // Save SP
+ SUB $8, R13 // R13 = R13 - 8
+ BIC $0x7, R13 // Align SP for ABI
+ RSB $0, R0, R3 // R3 = -R0
+ MOVW $0, R1 // R1 = FALSE (alertable)
+ MOVW $-1, R0 // R0 = handle
+ MOVW R13, R2 // R2 = pTime
+ MOVW R3, 0(R2) // time_lo
+ MOVW R0, 4(R2) // time_hi
+ MOVW runtime·_NtWaitForSingleObject(SB), R3
+ BL (R3)
+ MOVW R4, R13 // Restore SP
+ MOVM.IA.W (R13), [R4, R15] // pop {R4, pc}
+
+// Runs on OS stack. Duration (in 100ns units) is in R0.
+// TODO: neeeds to be implemented properly.
+TEXT runtime·usleep2HighRes(SB),NOSPLIT|NOFRAME,$0
+ B runtime·abort(SB)
+
+// Runs on OS stack.
+TEXT runtime·switchtothread(SB),NOSPLIT|NOFRAME,$0
+ MOVM.DB.W [R4, R14], (R13) // push {R4, lr}
+ MOVW R13, R4
+ BIC $0x7, R13 // alignment for ABI
+ MOVW runtime·_SwitchToThread(SB), R0
+ BL (R0)
+ MOVW R4, R13 // restore stack pointer
+ MOVM.IA.W (R13), [R4, R15] // pop {R4, pc}
+
+TEXT ·publicationBarrier(SB),NOSPLIT|NOFRAME,$0-0
+ B runtime·armPublicationBarrier(SB)
+
+// never called (cgo not supported)
+TEXT runtime·read_tls_fallback(SB),NOSPLIT|NOFRAME,$0
+ MOVW $0xabcd, R0
+ MOVW R0, (R0)
+ RET
+
+// See http://www.dcl.hpi.uni-potsdam.de/research/WRK/2007/08/getting-os-information-the-kuser_shared_data-structure/
+// Must read hi1, then lo, then hi2. The snapshot is valid if hi1 == hi2.
+#define _INTERRUPT_TIME 0x7ffe0008
+#define _SYSTEM_TIME 0x7ffe0014
+#define time_lo 0
+#define time_hi1 4
+#define time_hi2 8
+
+TEXT runtime·nanotime1(SB),NOSPLIT,$0-8
+ MOVW $0, R0
+ MOVB runtime·useQPCTime(SB), R0
+ CMP $0, R0
+ BNE useQPC
+ MOVW $_INTERRUPT_TIME, R3
+loop:
+ MOVW time_hi1(R3), R1
+ MOVW time_lo(R3), R0
+ MOVW time_hi2(R3), R2
+ CMP R1, R2
+ BNE loop
+
+ // wintime = R1:R0, multiply by 100
+ MOVW $100, R2
+ MULLU R0, R2, (R4, R3) // R4:R3 = R1:R0 * R2
+ MULA R1, R2, R4, R4
+
+ // wintime*100 = R4:R3
+ MOVW R3, ret_lo+0(FP)
+ MOVW R4, ret_hi+4(FP)
+ RET
+useQPC:
+ B runtime·nanotimeQPC(SB) // tail call
+ RET
+
+TEXT time·now(SB),NOSPLIT,$0-20
+ MOVW $0, R0
+ MOVB runtime·useQPCTime(SB), R0
+ CMP $0, R0
+ BNE useQPC
+ MOVW $_INTERRUPT_TIME, R3
+loop:
+ MOVW time_hi1(R3), R1
+ MOVW time_lo(R3), R0
+ MOVW time_hi2(R3), R2
+ CMP R1, R2
+ BNE loop
+
+ // wintime = R1:R0, multiply by 100
+ MOVW $100, R2
+ MULLU R0, R2, (R4, R3) // R4:R3 = R1:R0 * R2
+ MULA R1, R2, R4, R4
+
+ // wintime*100 = R4:R3
+ MOVW R3, mono+12(FP)
+ MOVW R4, mono+16(FP)
+
+ MOVW $_SYSTEM_TIME, R3
+wall:
+ MOVW time_hi1(R3), R1
+ MOVW time_lo(R3), R0
+ MOVW time_hi2(R3), R2
+ CMP R1, R2
+ BNE wall
+
+ // w = R1:R0 in 100ns untis
+ // convert to Unix epoch (but still 100ns units)
+ #define delta 116444736000000000
+ SUB.S $(delta & 0xFFFFFFFF), R0
+ SBC $(delta >> 32), R1
+
+ // Convert to nSec
+ MOVW $100, R2
+ MULLU R0, R2, (R4, R3) // R4:R3 = R1:R0 * R2
+ MULA R1, R2, R4, R4
+ // w = R2:R1 in nSec
+ MOVW R3, R1 // R4:R3 -> R2:R1
+ MOVW R4, R2
+
+ // multiply nanoseconds by reciprocal of 10**9 (scaled by 2**61)
+ // to get seconds (96 bit scaled result)
+ MOVW $0x89705f41, R3 // 2**61 * 10**-9
+ MULLU R1,R3,(R6,R5) // R7:R6:R5 = R2:R1 * R3
+ MOVW $0,R7
+ MULALU R2,R3,(R7,R6)
+
+ // unscale by discarding low 32 bits, shifting the rest by 29
+ MOVW R6>>29,R6 // R7:R6 = (R7:R6:R5 >> 61)
+ ORR R7<<3,R6
+ MOVW R7>>29,R7
+
+ // subtract (10**9 * sec) from nsec to get nanosecond remainder
+ MOVW $1000000000, R5 // 10**9
+ MULLU R6,R5,(R9,R8) // R9:R8 = R7:R6 * R5
+ MULA R7,R5,R9,R9
+ SUB.S R8,R1 // R2:R1 -= R9:R8
+ SBC R9,R2
+
+ // because reciprocal was a truncated repeating fraction, quotient
+ // may be slightly too small -- adjust to make remainder < 10**9
+ CMP R5,R1 // if remainder > 10**9
+ SUB.HS R5,R1 // remainder -= 10**9
+ ADD.HS $1,R6 // sec += 1
+
+ MOVW R6,sec_lo+0(FP)
+ MOVW R7,sec_hi+4(FP)
+ MOVW R1,nsec+8(FP)
+ RET
+useQPC:
+ B runtime·nanotimeQPC(SB) // tail call
+ RET
+
+// save_g saves the g register (R10) into thread local memory
+// so that we can call externally compiled
+// ARM code that will overwrite those registers.
+// NOTE: runtime.gogo assumes that R1 is preserved by this function.
+// runtime.mcall assumes this function only clobbers R0 and R11.
+// Returns with g in R0.
+// Save the value in the _TEB->TlsSlots array.
+// Effectively implements TlsSetValue().
+// tls_g stores the TLS slot allocated TlsAlloc().
+TEXT runtime·save_g(SB),NOSPLIT|NOFRAME,$0
+ MRC 15, 0, R0, C13, C0, 2
+ ADD $0xe10, R0
+ MOVW $runtime·tls_g(SB), R11
+ MOVW (R11), R11
+ MOVW g, R11<<2(R0)
+ MOVW g, R0 // preserve R0 across call to setg<>
+ RET
+
+// load_g loads the g register from thread-local memory,
+// for use after calling externally compiled
+// ARM code that overwrote those registers.
+// Get the value from the _TEB->TlsSlots array.
+// Effectively implements TlsGetValue().
+TEXT runtime·load_g(SB),NOSPLIT|NOFRAME,$0
+ MRC 15, 0, R0, C13, C0, 2
+ ADD $0xe10, R0
+ MOVW $runtime·tls_g(SB), g
+ MOVW (g), g
+ MOVW g<<2(R0), g
+ RET
+
+// This is called from rt0_go, which runs on the system stack
+// using the initial stack allocated by the OS.
+// It calls back into standard C using the BL below.
+// To do that, the stack pointer must be 8-byte-aligned.
+TEXT runtime·_initcgo(SB),NOSPLIT|NOFRAME,$0
+ MOVM.DB.W [R4, R14], (R13) // push {r4, lr}
+
+ // Ensure stack is 8-byte aligned before calling C code
+ MOVW R13, R4
+ BIC $0x7, R13
+
+ // Allocate a TLS slot to hold g across calls to external code
+ MOVW $runtime·_TlsAlloc(SB), R0
+ MOVW (R0), R0
+ BL (R0)
+
+ // Assert that slot is less than 64 so we can use _TEB->TlsSlots
+ CMP $64, R0
+ MOVW $runtime·abort(SB), R1
+ BL.GE (R1)
+
+ // Save Slot into tls_g
+ MOVW $runtime·tls_g(SB), R1
+ MOVW R0, (R1)
+
+ BL init_thread_tls<>(SB)
+
+ MOVW R4, R13
+ MOVM.IA.W (R13), [R4, R15] // pop {r4, pc}
+
+// void init_thread_tls()
+//
+// Does per-thread TLS initialization. Saves a pointer to the TLS slot
+// holding G, in the current m.
+//
+// g->m->tls[0] = &_TEB->TlsSlots[tls_g]
+//
+// The purpose of this is to enable the profiling handler to get the
+// current g associated with the thread. We cannot use m->curg because curg
+// only holds the current user g. If the thread is executing system code or
+// external code, m->curg will be NULL. The thread's TLS slot always holds
+// the current g, so save a reference to this location so the profiling
+// handler can get the real g from the thread's m.
+//
+// Clobbers R0-R3
+TEXT init_thread_tls<>(SB),NOSPLIT|NOFRAME,$0
+ // compute &_TEB->TlsSlots[tls_g]
+ MRC 15, 0, R0, C13, C0, 2
+ ADD $0xe10, R0
+ MOVW $runtime·tls_g(SB), R1
+ MOVW (R1), R1
+ MOVW R1<<2, R1
+ ADD R1, R0
+
+ // save in g->m->tls[0]
+ MOVW g_m(g), R1
+ MOVW R0, m_tls(R1)
+ RET
+
+// Holds the TLS Slot, which was allocated by TlsAlloc()
+GLOBL runtime·tls_g+0(SB), NOPTR, $4