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go/src/runtime/sys_linux_arm.s
Ian Lance Taylor 419c06455a runtime: get traceback from VDSO code 
Currently if a profiling signal arrives while executing within a VDSO
the profiler will report _ExternalCode, which is needlessly confusing
for a pure Go program. Change the VDSO calling code to record the
caller's PC/SP, so that we can do a traceback from that point. If that
fails for some reason, report _VDSO rather than _ExternalCode, which
should at least point in the right direction.

This adds some instructions to the code that calls the VDSO, but the
slowdown is reasonably negligible:

name                                  old time/op  new time/op  delta
ClockVDSOAndFallbackPaths/vDSO-8      40.5ns ± 2%  41.3ns ± 1%  +1.85%  (p=0.002 n=10+10)
ClockVDSOAndFallbackPaths/Fallback-8  41.9ns ± 1%  43.5ns ± 1%  +3.84%  (p=0.000 n=9+9)
TimeNow-8                             41.5ns ± 3%  41.5ns ± 2%    ~     (p=0.723 n=10+10)

Fixes #24142

Change-Id: Iacd935db3c4c782150b3809aaa675a71799b1c9c
Reviewed-on: https://go-review.googlesource.com/97315
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
2018-03-07 23:35:25 +00:00

604 lines
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// Copyright 2009 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.
//
// System calls and other sys.stuff for arm, Linux
//
#include "go_asm.h"
#include "go_tls.h"
#include "textflag.h"
#define CLOCK_REALTIME 0
#define CLOCK_MONOTONIC 1
// for EABI, as we don't support OABI
#define SYS_BASE 0x0
#define SYS_exit (SYS_BASE + 1)
#define SYS_read (SYS_BASE + 3)
#define SYS_write (SYS_BASE + 4)
#define SYS_open (SYS_BASE + 5)
#define SYS_close (SYS_BASE + 6)
#define SYS_getpid (SYS_BASE + 20)
#define SYS_kill (SYS_BASE + 37)
#define SYS_clone (SYS_BASE + 120)
#define SYS_rt_sigreturn (SYS_BASE + 173)
#define SYS_rt_sigaction (SYS_BASE + 174)
#define SYS_rt_sigprocmask (SYS_BASE + 175)
#define SYS_sigaltstack (SYS_BASE + 186)
#define SYS_mmap2 (SYS_BASE + 192)
#define SYS_futex (SYS_BASE + 240)
#define SYS_exit_group (SYS_BASE + 248)
#define SYS_munmap (SYS_BASE + 91)
#define SYS_madvise (SYS_BASE + 220)
#define SYS_setitimer (SYS_BASE + 104)
#define SYS_mincore (SYS_BASE + 219)
#define SYS_gettid (SYS_BASE + 224)
#define SYS_tkill (SYS_BASE + 238)
#define SYS_sched_yield (SYS_BASE + 158)
#define SYS_pselect6 (SYS_BASE + 335)
#define SYS_sched_getaffinity (SYS_BASE + 242)
#define SYS_clock_gettime (SYS_BASE + 263)
#define SYS_epoll_create (SYS_BASE + 250)
#define SYS_epoll_ctl (SYS_BASE + 251)
#define SYS_epoll_wait (SYS_BASE + 252)
#define SYS_epoll_create1 (SYS_BASE + 357)
#define SYS_fcntl (SYS_BASE + 55)
#define SYS_access (SYS_BASE + 33)
#define SYS_connect (SYS_BASE + 283)
#define SYS_socket (SYS_BASE + 281)
#define SYS_brk (SYS_BASE + 45)
#define ARM_BASE (SYS_BASE + 0x0f0000)
TEXT runtime·open(SB),NOSPLIT,$0
MOVW name+0(FP), R0
MOVW mode+4(FP), R1
MOVW perm+8(FP), R2
MOVW $SYS_open, R7
SWI $0
MOVW $0xfffff001, R1
CMP R1, R0
MOVW.HI $-1, R0
MOVW R0, ret+12(FP)
RET
TEXT runtime·closefd(SB),NOSPLIT,$0
MOVW fd+0(FP), R0
MOVW $SYS_close, R7
SWI $0
MOVW $0xfffff001, R1
CMP R1, R0
MOVW.HI $-1, R0
MOVW R0, ret+4(FP)
RET
TEXT runtime·write(SB),NOSPLIT,$0
MOVW fd+0(FP), R0
MOVW p+4(FP), R1
MOVW n+8(FP), R2
MOVW $SYS_write, R7
SWI $0
MOVW $0xfffff001, R1
CMP R1, R0
MOVW.HI $-1, R0
MOVW R0, ret+12(FP)
RET
TEXT runtime·read(SB),NOSPLIT,$0
MOVW fd+0(FP), R0
MOVW p+4(FP), R1
MOVW n+8(FP), R2
MOVW $SYS_read, R7
SWI $0
MOVW $0xfffff001, R1
CMP R1, R0
MOVW.HI $-1, R0
MOVW R0, ret+12(FP)
RET
TEXT runtime·exit(SB),NOSPLIT|NOFRAME,$0
MOVW code+0(FP), R0
MOVW $SYS_exit_group, R7
SWI $0
MOVW $1234, R0
MOVW $1002, R1
MOVW R0, (R1) // fail hard
TEXT exit1<>(SB),NOSPLIT|NOFRAME,$0
MOVW code+0(FP), R0
MOVW $SYS_exit, R7
SWI $0
MOVW $1234, R0
MOVW $1003, R1
MOVW R0, (R1) // fail hard
// func exitThread(wait *uint32)
TEXT runtime·exitThread(SB),NOSPLIT|NOFRAME,$0-4
MOVW wait+0(FP), R0
// We're done using the stack.
// Alas, there's no reliable way to make this write atomic
// without potentially using the stack. So it goes.
MOVW $0, R1
MOVW R1, (R0)
MOVW $0, R0 // exit code
MOVW $SYS_exit, R7
SWI $0
MOVW $1234, R0
MOVW $1004, R1
MOVW R0, (R1) // fail hard
JMP 0(PC)
TEXT runtime·gettid(SB),NOSPLIT,$0-4
MOVW $SYS_gettid, R7
SWI $0
MOVW R0, ret+0(FP)
RET
TEXT runtime·raise(SB),NOSPLIT|NOFRAME,$0
MOVW $SYS_gettid, R7
SWI $0
// arg 1 tid already in R0 from gettid
MOVW sig+0(FP), R1 // arg 2 - signal
MOVW $SYS_tkill, R7
SWI $0
RET
TEXT runtime·raiseproc(SB),NOSPLIT|NOFRAME,$0
MOVW $SYS_getpid, R7
SWI $0
// arg 1 tid already in R0 from getpid
MOVW sig+0(FP), R1 // arg 2 - signal
MOVW $SYS_kill, R7
SWI $0
RET
TEXT runtime·mmap(SB),NOSPLIT,$0
MOVW addr+0(FP), R0
MOVW n+4(FP), R1
MOVW prot+8(FP), R2
MOVW flags+12(FP), R3
MOVW fd+16(FP), R4
MOVW off+20(FP), R5
MOVW $SYS_mmap2, R7
SWI $0
MOVW $0xfffff001, R6
CMP R6, R0
MOVW $0, R1
RSB.HI $0, R0
MOVW.HI R0, R1 // if error, put in R1
MOVW.HI $0, R0
MOVW R0, p+24(FP)
MOVW R1, err+28(FP)
RET
TEXT runtime·munmap(SB),NOSPLIT,$0
MOVW addr+0(FP), R0
MOVW n+4(FP), R1
MOVW $SYS_munmap, R7
SWI $0
MOVW $0xfffff001, R6
CMP R6, R0
MOVW.HI $0, R8 // crash on syscall failure
MOVW.HI R8, (R8)
RET
TEXT runtime·madvise(SB),NOSPLIT,$0
MOVW addr+0(FP), R0
MOVW n+4(FP), R1
MOVW flags+8(FP), R2
MOVW $SYS_madvise, R7
SWI $0
// ignore failure - maybe pages are locked
RET
TEXT runtime·setitimer(SB),NOSPLIT,$0
MOVW mode+0(FP), R0
MOVW new+4(FP), R1
MOVW old+8(FP), R2
MOVW $SYS_setitimer, R7
SWI $0
RET
TEXT runtime·mincore(SB),NOSPLIT,$0
MOVW addr+0(FP), R0
MOVW n+4(FP), R1
MOVW dst+8(FP), R2
MOVW $SYS_mincore, R7
SWI $0
MOVW R0, ret+12(FP)
RET
TEXT runtime·walltime(SB),NOSPLIT,$0-12
// We don't know how much stack space the VDSO code will need,
// so switch to g0.
// Save old SP. Use R13 instead of SP to avoid linker rewriting the offsets.
MOVW R13, R4 // R4 is unchanged by C code.
MOVW g_m(g), R5 // R5 is unchanged by C code.
// Set vdsoPC and vdsoSP for SIGPROF traceback.
MOVW LR, m_vdsoPC(R5)
MOVW R13, m_vdsoSP(R5)
MOVW m_curg(R5), R0
CMP g, R0 // Only switch if on curg.
B.NE noswitch
MOVW m_g0(R5), R0
MOVW (g_sched+gobuf_sp)(R0), R13 // Set SP to g0 stack
noswitch:
SUB $24, R13 // Space for results
BIC $0x7, R13 // Align for C code
MOVW $CLOCK_REALTIME, R0
MOVW $8(R13), R1 // timespec
MOVW runtime·vdsoClockgettimeSym(SB), R11
CMP $0, R11
B.EQ fallback
BL (R11)
JMP finish
fallback:
MOVW $SYS_clock_gettime, R7
SWI $0
finish:
MOVW 8(R13), R0 // sec
MOVW 12(R13), R2 // nsec
MOVW R4, R13 // Restore real SP
MOVW $0, R1
MOVW R1, m_vdsoSP(R5)
MOVW R0, sec_lo+0(FP)
MOVW R1, sec_hi+4(FP)
MOVW R2, nsec+8(FP)
RET
// int64 nanotime(void)
TEXT runtime·nanotime(SB),NOSPLIT,$0-8
// Switch to g0 stack. See comment above in runtime·walltime.
// Save old SP. Use R13 instead of SP to avoid linker rewriting the offsets.
MOVW R13, R4 // R4 is unchanged by C code.
MOVW g_m(g), R5 // R5 is unchanged by C code.
// Set vdsoPC and vdsoSP for SIGPROF traceback.
MOVW LR, m_vdsoPC(R5)
MOVW R13, m_vdsoSP(R5)
MOVW m_curg(R5), R0
CMP g, R0 // Only switch if on curg.
B.NE noswitch
MOVW m_g0(R5), R0
MOVW (g_sched+gobuf_sp)(R0), R13 // Set SP to g0 stack
noswitch:
SUB $24, R13 // Space for results
BIC $0x7, R13 // Align for C code
MOVW $CLOCK_MONOTONIC, R0
MOVW $8(R13), R1 // timespec
MOVW runtime·vdsoClockgettimeSym(SB), R11
CMP $0, R11
B.EQ fallback
BL (R11)
JMP finish
fallback:
MOVW $SYS_clock_gettime, R7
SWI $0
finish:
MOVW 8(R13), R0 // sec
MOVW 12(R13), R2 // nsec
MOVW R4, R13 // Restore real SP
MOVW $0, R4
MOVW R4, m_vdsoSP(R5)
MOVW $1000000000, R3
MULLU R0, R3, (R1, R0)
ADD.S R2, R0
ADC R4, R1
MOVW R0, ret_lo+0(FP)
MOVW R1, ret_hi+4(FP)
RET
// int32 futex(int32 *uaddr, int32 op, int32 val,
// struct timespec *timeout, int32 *uaddr2, int32 val2);
TEXT runtime·futex(SB),NOSPLIT,$0
MOVW addr+0(FP), R0
MOVW op+4(FP), R1
MOVW val+8(FP), R2
MOVW ts+12(FP), R3
MOVW addr2+16(FP), R4
MOVW val3+20(FP), R5
MOVW $SYS_futex, R7
SWI $0
MOVW R0, ret+24(FP)
RET
// int32 clone(int32 flags, void *stack, M *mp, G *gp, void (*fn)(void));
TEXT runtime·clone(SB),NOSPLIT,$0
MOVW flags+0(FP), R0
MOVW stk+4(FP), R1
MOVW $0, R2 // parent tid ptr
MOVW $0, R3 // tls_val
MOVW $0, R4 // child tid ptr
MOVW $0, R5
// Copy mp, gp, fn off parent stack for use by child.
// TODO(kaib): figure out which registers are clobbered by clone and avoid stack copying
MOVW $-16(R1), R1
MOVW mp+8(FP), R6
MOVW R6, 0(R1)
MOVW gp+12(FP), R6
MOVW R6, 4(R1)
MOVW fn+16(FP), R6
MOVW R6, 8(R1)
MOVW $1234, R6
MOVW R6, 12(R1)
MOVW $SYS_clone, R7
SWI $0
// In parent, return.
CMP $0, R0
BEQ 3(PC)
MOVW R0, ret+20(FP)
RET
// Paranoia: check that SP is as we expect. Use R13 to avoid linker 'fixup'
MOVW 12(R13), R0
MOVW $1234, R1
CMP R0, R1
BEQ 2(PC)
BL runtime·abort(SB)
MOVW 0(R13), R8 // m
MOVW 4(R13), R0 // g
CMP $0, R8
BEQ nog
CMP $0, R0
BEQ nog
MOVW R0, g
MOVW R8, g_m(g)
// paranoia; check they are not nil
MOVW 0(R8), R0
MOVW 0(g), R0
BL runtime·emptyfunc(SB) // fault if stack check is wrong
// Initialize m->procid to Linux tid
MOVW $SYS_gettid, R7
SWI $0
MOVW g_m(g), R8
MOVW R0, m_procid(R8)
nog:
// Call fn
MOVW 8(R13), R0
MOVW $16(R13), R13
BL (R0)
// It shouldn't return. If it does, exit that thread.
SUB $16, R13 // restore the stack pointer to avoid memory corruption
MOVW $0, R0
MOVW R0, 4(R13)
BL exit1<>(SB)
MOVW $1234, R0
MOVW $1005, R1
MOVW R0, (R1)
TEXT runtime·sigaltstack(SB),NOSPLIT,$0
MOVW new+0(FP), R0
MOVW old+4(FP), R1
MOVW $SYS_sigaltstack, R7
SWI $0
MOVW $0xfffff001, R6
CMP R6, R0
MOVW.HI $0, R8 // crash on syscall failure
MOVW.HI R8, (R8)
RET
TEXT runtime·sigfwd(SB),NOSPLIT,$0-16
MOVW sig+4(FP), R0
MOVW info+8(FP), R1
MOVW ctx+12(FP), R2
MOVW fn+0(FP), R11
MOVW R13, R4
SUB $24, R13
BIC $0x7, R13 // alignment for ELF ABI
BL (R11)
MOVW R4, R13
RET
TEXT runtime·sigtramp(SB),NOSPLIT,$12
// this might be called in external code context,
// where g is not set.
// first save R0, because runtime·load_g will clobber it
MOVW R0, 4(R13)
MOVB runtime·iscgo(SB), R0
CMP $0, R0
BL.NE runtime·load_g(SB)
MOVW R1, 8(R13)
MOVW R2, 12(R13)
MOVW $runtime·sigtrampgo(SB), R11
BL (R11)
RET
TEXT runtime·cgoSigtramp(SB),NOSPLIT,$0
MOVW $runtime·sigtramp(SB), R11
B (R11)
TEXT runtime·rtsigprocmask(SB),NOSPLIT,$0
MOVW how+0(FP), R0
MOVW new+4(FP), R1
MOVW old+8(FP), R2
MOVW size+12(FP), R3
MOVW $SYS_rt_sigprocmask, R7
SWI $0
RET
TEXT runtime·rt_sigaction(SB),NOSPLIT,$0
MOVW sig+0(FP), R0
MOVW new+4(FP), R1
MOVW old+8(FP), R2
MOVW size+12(FP), R3
MOVW $SYS_rt_sigaction, R7
SWI $0
MOVW R0, ret+16(FP)
RET
TEXT runtime·usleep(SB),NOSPLIT,$12
MOVW usec+0(FP), R0
CALL runtime·usplitR0(SB)
MOVW R0, 4(R13)
MOVW $1000, R0 // usec to nsec
MUL R0, R1
MOVW R1, 8(R13)
MOVW $0, R0
MOVW $0, R1
MOVW $0, R2
MOVW $0, R3
MOVW $4(R13), R4
MOVW $0, R5
MOVW $SYS_pselect6, R7
SWI $0
RET
// As for cas, memory barriers are complicated on ARM, but the kernel
// provides a user helper. ARMv5 does not support SMP and has no
// memory barrier instruction at all. ARMv6 added SMP support and has
// a memory barrier, but it requires writing to a coprocessor
// register. ARMv7 introduced the DMB instruction, but it's expensive
// even on single-core devices. The kernel helper takes care of all of
// this for us.
TEXT publicationBarrier<>(SB),NOSPLIT,$0
// void __kuser_memory_barrier(void);
MOVW $0xffff0fa0, R15 // R15 is hardware PC.
TEXT ·publicationBarrier(SB),NOSPLIT,$0
BL publicationBarrier<>(SB)
RET
TEXT runtime·osyield(SB),NOSPLIT,$0
MOVW $SYS_sched_yield, R7
SWI $0
RET
TEXT runtime·sched_getaffinity(SB),NOSPLIT,$0
MOVW pid+0(FP), R0
MOVW len+4(FP), R1
MOVW buf+8(FP), R2
MOVW $SYS_sched_getaffinity, R7
SWI $0
MOVW R0, ret+12(FP)
RET
// int32 runtime·epollcreate(int32 size)
TEXT runtime·epollcreate(SB),NOSPLIT,$0
MOVW size+0(FP), R0
MOVW $SYS_epoll_create, R7
SWI $0
MOVW R0, ret+4(FP)
RET
// int32 runtime·epollcreate1(int32 flags)
TEXT runtime·epollcreate1(SB),NOSPLIT,$0
MOVW flags+0(FP), R0
MOVW $SYS_epoll_create1, R7
SWI $0
MOVW R0, ret+4(FP)
RET
// func epollctl(epfd, op, fd int32, ev *epollEvent) int
TEXT runtime·epollctl(SB),NOSPLIT,$0
MOVW epfd+0(FP), R0
MOVW op+4(FP), R1
MOVW fd+8(FP), R2
MOVW ev+12(FP), R3
MOVW $SYS_epoll_ctl, R7
SWI $0
MOVW R0, ret+16(FP)
RET
// int32 runtime·epollwait(int32 epfd, EpollEvent *ev, int32 nev, int32 timeout)
TEXT runtime·epollwait(SB),NOSPLIT,$0
MOVW epfd+0(FP), R0
MOVW ev+4(FP), R1
MOVW nev+8(FP), R2
MOVW timeout+12(FP), R3
MOVW $SYS_epoll_wait, R7
SWI $0
MOVW R0, ret+16(FP)
RET
// void runtime·closeonexec(int32 fd)
TEXT runtime·closeonexec(SB),NOSPLIT,$0
MOVW fd+0(FP), R0 // fd
MOVW $2, R1 // F_SETFD
MOVW $1, R2 // FD_CLOEXEC
MOVW $SYS_fcntl, R7
SWI $0
RET
// b __kuser_get_tls @ 0xffff0fe0
TEXT runtime·read_tls_fallback(SB),NOSPLIT|NOFRAME,$0
MOVW $0xffff0fe0, R0
B (R0)
TEXT runtime·access(SB),NOSPLIT,$0
MOVW name+0(FP), R0
MOVW mode+4(FP), R1
MOVW $SYS_access, R7
SWI $0
MOVW R0, ret+8(FP)
RET
TEXT runtime·connect(SB),NOSPLIT,$0
MOVW fd+0(FP), R0
MOVW addr+4(FP), R1
MOVW len+8(FP), R2
MOVW $SYS_connect, R7
SWI $0
MOVW R0, ret+12(FP)
RET
TEXT runtime·socket(SB),NOSPLIT,$0
MOVW domain+0(FP), R0
MOVW typ+4(FP), R1
MOVW prot+8(FP), R2
MOVW $SYS_socket, R7
SWI $0
MOVW R0, ret+12(FP)
RET
// func sbrk0() uintptr
TEXT runtime·sbrk0(SB),NOSPLIT,$0-4
// Implemented as brk(NULL).
MOVW $0, R0
MOVW $SYS_brk, R7
SWI $0
MOVW R0, ret+0(FP)
RET
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