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go/src/runtime/sys_linux_arm64.s
Austin Clements bb6309cd63 runtime: inform arena placement using sbrk(0) 
On 32-bit architectures (or if we fail to map a 64-bit-style arena),
we try to map the heap arena just above the end of the process image.
While we can accept any address, using lower addresses is preferable
because lower addresses cause us to map less of the heap bitmap.

However, if a program is linked against C code that has global
constructors, those constructors may call brk/sbrk to allocate memory
(e.g., many C malloc implementations do this for small allocations).
The brk also starts just above the process image, so this may adjust
the brk past the beginning of where we want to put the heap arena. In
this case, the kernel will pick a different address for the arena and
it will usually be very high (at least, as these things go in a 32-bit
address space).

Fix this by consulting the current value of the brk and using this in
addition to the end of the process image to compute the initial arena
placement.

This is implemented only on Linux currently, since we have no evidence
that it's an issue on any other OSes.

Fixes #19831.

Change-Id: Id64b45d08d8c91e4f50d92d0339146250b04f2f8
Reviewed-on: https://go-review.googlesource.com/39810
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
2017-04-21 14:34:10 +00:00

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// Copyright 2014 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 arm64, Linux
//
#include "go_asm.h"
#include "go_tls.h"
#include "textflag.h"
#define AT_FDCWD -100
#define SYS_exit 93
#define SYS_read 63
#define SYS_write 64
#define SYS_openat 56
#define SYS_close 57
#define SYS_fcntl 25
#define SYS_gettimeofday 169
#define SYS_pselect6 72
#define SYS_mmap 222
#define SYS_munmap 215
#define SYS_setitimer 103
#define SYS_clone 220
#define SYS_sched_yield 124
#define SYS_rt_sigreturn 139
#define SYS_rt_sigaction 134
#define SYS_rt_sigprocmask 135
#define SYS_sigaltstack 132
#define SYS_getrlimit 163
#define SYS_madvise 233
#define SYS_mincore 232
#define SYS_getpid 172
#define SYS_gettid 178
#define SYS_kill 129
#define SYS_tkill 130
#define SYS_futex 98
#define SYS_sched_getaffinity 123
#define SYS_exit_group 94
#define SYS_epoll_create1 20
#define SYS_epoll_ctl 21
#define SYS_epoll_pwait 22
#define SYS_clock_gettime 113
#define SYS_faccessat 48
#define SYS_socket 198
#define SYS_connect 203
#define SYS_brk 214
TEXT runtime·exit(SB),NOSPLIT,$-8-4
MOVW code+0(FP), R0
MOVD $SYS_exit_group, R8
SVC
RET
TEXT runtime·exit1(SB),NOSPLIT,$-8-4
MOVW code+0(FP), R0
MOVD $SYS_exit, R8
SVC
RET
TEXT runtime·open(SB),NOSPLIT,$-8-20
MOVD $AT_FDCWD, R0
MOVD name+0(FP), R1
MOVW mode+8(FP), R2
MOVW perm+12(FP), R3
MOVD $SYS_openat, R8
SVC
CMN $4095, R0
BCC done
MOVW $-1, R0
done:
MOVW R0, ret+16(FP)
RET
TEXT runtime·closefd(SB),NOSPLIT,$-8-12
MOVW fd+0(FP), R0
MOVD $SYS_close, R8
SVC
CMN $4095, R0
BCC done
MOVW $-1, R0
done:
MOVW R0, ret+8(FP)
RET
TEXT runtime·write(SB),NOSPLIT,$-8-28
MOVD fd+0(FP), R0
MOVD p+8(FP), R1
MOVW n+16(FP), R2
MOVD $SYS_write, R8
SVC
CMN $4095, R0
BCC done
MOVW $-1, R0
done:
MOVW R0, ret+24(FP)
RET
TEXT runtime·read(SB),NOSPLIT,$-8-28
MOVW fd+0(FP), R0
MOVD p+8(FP), R1
MOVW n+16(FP), R2
MOVD $SYS_read, R8
SVC
CMN $4095, R0
BCC done
MOVW $-1, R0
done:
MOVW R0, ret+24(FP)
RET
TEXT runtime·getrlimit(SB),NOSPLIT,$-8-20
MOVW kind+0(FP), R0
MOVD limit+8(FP), R1
MOVD $SYS_getrlimit, R8
SVC
MOVW R0, ret+16(FP)
RET
TEXT runtime·usleep(SB),NOSPLIT,$24-4
MOVWU usec+0(FP), R3
MOVD R3, R5
MOVW $1000000, R4
UDIV R4, R3
MOVD R3, 8(RSP)
MUL R3, R4
SUB R4, R5
MOVW $1000, R4
MUL R4, R5
MOVD R5, 16(RSP)
// pselect6(0, 0, 0, 0, &ts, 0)
MOVD $0, R0
MOVD R0, R1
MOVD R0, R2
MOVD R0, R3
ADD $8, RSP, R4
MOVD R0, R5
MOVD $SYS_pselect6, R8
SVC
RET
TEXT runtime·gettid(SB),NOSPLIT,$0-4
MOVD $SYS_gettid, R8
SVC
MOVW R0, ret+0(FP)
RET
TEXT runtime·raise(SB),NOSPLIT,$-8
MOVD $SYS_gettid, R8
SVC
MOVW R0, R0 // arg 1 tid
MOVW sig+0(FP), R1 // arg 2
MOVD $SYS_tkill, R8
SVC
RET
TEXT runtime·raiseproc(SB),NOSPLIT,$-8
MOVD $SYS_getpid, R8
SVC
MOVW R0, R0 // arg 1 pid
MOVW sig+0(FP), R1 // arg 2
MOVD $SYS_kill, R8
SVC
RET
TEXT runtime·setitimer(SB),NOSPLIT,$-8-24
MOVW mode+0(FP), R0
MOVD new+8(FP), R1
MOVD old+16(FP), R2
MOVD $SYS_setitimer, R8
SVC
RET
TEXT runtime·mincore(SB),NOSPLIT,$-8-28
MOVD addr+0(FP), R0
MOVD n+8(FP), R1
MOVD dst+16(FP), R2
MOVD $SYS_mincore, R8
SVC
MOVW R0, ret+24(FP)
RET
// func walltime() (sec int64, nsec int32)
TEXT runtime·walltime(SB),NOSPLIT,$24-12
MOVW $0, R0 // CLOCK_REALTIME
MOVD RSP, R1
MOVD $SYS_clock_gettime, R8
SVC
MOVD 0(RSP), R3 // sec
MOVD 8(RSP), R5 // nsec
MOVD R3, sec+0(FP)
MOVW R5, nsec+8(FP)
RET
TEXT runtime·nanotime(SB),NOSPLIT,$24-8
MOVW $1, R0 // CLOCK_MONOTONIC
MOVD RSP, R1
MOVD $SYS_clock_gettime, R8
SVC
MOVD 0(RSP), R3 // sec
MOVD 8(RSP), R5 // nsec
// sec is in R3, nsec in R5
// return nsec in R3
MOVD $1000000000, R4
MUL R4, R3
ADD R5, R3
MOVD R3, ret+0(FP)
RET
TEXT runtime·rtsigprocmask(SB),NOSPLIT,$-8-28
MOVW how+0(FP), R0
MOVD new+8(FP), R1
MOVD old+16(FP), R2
MOVW size+24(FP), R3
MOVD $SYS_rt_sigprocmask, R8
SVC
CMN $4095, R0
BCC done
MOVD $0, R0
MOVD R0, (R0) // crash
done:
RET
TEXT runtime·rt_sigaction(SB),NOSPLIT,$-8-36
MOVD sig+0(FP), R0
MOVD new+8(FP), R1
MOVD old+16(FP), R2
MOVD size+24(FP), R3
MOVD $SYS_rt_sigaction, R8
SVC
MOVW R0, ret+32(FP)
RET
TEXT runtime·sigfwd(SB),NOSPLIT,$0-32
MOVW sig+8(FP), R0
MOVD info+16(FP), R1
MOVD ctx+24(FP), R2
MOVD fn+0(FP), R11
BL (R11)
RET
TEXT runtime·sigtramp(SB),NOSPLIT,$24
// 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, 8(RSP)
MOVBU runtime·iscgo(SB), R0
CMP $0, R0
BEQ 2(PC)
BL runtime·load_g(SB)
MOVD R1, 16(RSP)
MOVD R2, 24(RSP)
MOVD $runtime·sigtrampgo(SB), R0
BL (R0)
RET
TEXT runtime·cgoSigtramp(SB),NOSPLIT,$0
MOVD $runtime·sigtramp(SB), R3
B (R3)
TEXT runtime·mmap(SB),NOSPLIT,$-8
MOVD addr+0(FP), R0
MOVD n+8(FP), R1
MOVW prot+16(FP), R2
MOVW flags+20(FP), R3
MOVW fd+24(FP), R4
MOVW off+28(FP), R5
MOVD $SYS_mmap, R8
SVC
CMN $4095, R0
BCC 2(PC)
NEG R0,R0
MOVD R0, ret+32(FP)
RET
TEXT runtime·munmap(SB),NOSPLIT,$-8
MOVD addr+0(FP), R0
MOVD n+8(FP), R1
MOVD $SYS_munmap, R8
SVC
CMN $4095, R0
BCC cool
MOVD R0, 0xf0(R0)
cool:
RET
TEXT runtime·madvise(SB),NOSPLIT,$-8
MOVD addr+0(FP), R0
MOVD n+8(FP), R1
MOVW flags+16(FP), R2
MOVD $SYS_madvise, R8
SVC
// ignore failure - maybe pages are locked
RET
// int64 futex(int32 *uaddr, int32 op, int32 val,
// struct timespec *timeout, int32 *uaddr2, int32 val2);
TEXT runtime·futex(SB),NOSPLIT,$-8
MOVD addr+0(FP), R0
MOVW op+8(FP), R1
MOVW val+12(FP), R2
MOVD ts+16(FP), R3
MOVD addr2+24(FP), R4
MOVW val3+32(FP), R5
MOVD $SYS_futex, R8
SVC
MOVW R0, ret+40(FP)
RET
// int64 clone(int32 flags, void *stk, M *mp, G *gp, void (*fn)(void));
TEXT runtime·clone(SB),NOSPLIT,$-8
MOVW flags+0(FP), R0
MOVD stk+8(FP), R1
// Copy mp, gp, fn off parent stack for use by child.
MOVD mp+16(FP), R10
MOVD gp+24(FP), R11
MOVD fn+32(FP), R12
MOVD R10, -8(R1)
MOVD R11, -16(R1)
MOVD R12, -24(R1)
MOVD $1234, R10
MOVD R10, -32(R1)
MOVD $SYS_clone, R8
SVC
// In parent, return.
CMP ZR, R0
BEQ child
MOVW R0, ret+40(FP)
RET
child:
// In child, on new stack.
MOVD -32(RSP), R10
MOVD $1234, R0
CMP R0, R10
BEQ good
MOVD $0, R0
MOVD R0, (R0) // crash
good:
// Initialize m->procid to Linux tid
MOVD $SYS_gettid, R8
SVC
MOVD -24(RSP), R12 // fn
MOVD -16(RSP), R11 // g
MOVD -8(RSP), R10 // m
CMP $0, R10
BEQ nog
CMP $0, R11
BEQ nog
MOVD R0, m_procid(R10)
// TODO: setup TLS.
// In child, set up new stack
MOVD R10, g_m(R11)
MOVD R11, g
//CALL runtime·stackcheck(SB)
nog:
// Call fn
MOVD R12, R0
BL (R0)
// It shouldn't return. If it does, exit that thread.
MOVW $111, R0
again:
MOVD $SYS_exit, R8
SVC
B again // keep exiting
TEXT runtime·sigaltstack(SB),NOSPLIT,$-8
MOVD new+0(FP), R0
MOVD old+8(FP), R1
MOVD $SYS_sigaltstack, R8
SVC
CMN $4095, R0
BCC ok
MOVD $0, R0
MOVD R0, (R0) // crash
ok:
RET
TEXT runtime·osyield(SB),NOSPLIT,$-8
MOVD $SYS_sched_yield, R8
SVC
RET
TEXT runtime·sched_getaffinity(SB),NOSPLIT,$-8
MOVD pid+0(FP), R0
MOVD len+8(FP), R1
MOVD buf+16(FP), R2
MOVD $SYS_sched_getaffinity, R8
SVC
MOVW R0, ret+24(FP)
RET
// int32 runtime·epollcreate(int32 size);
TEXT runtime·epollcreate(SB),NOSPLIT,$-8
MOVW $0, R0
MOVD $SYS_epoll_create1, R8
SVC
MOVW R0, ret+8(FP)
RET
// int32 runtime·epollcreate1(int32 flags);
TEXT runtime·epollcreate1(SB),NOSPLIT,$-8
MOVW flags+0(FP), R0
MOVD $SYS_epoll_create1, R8
SVC
MOVW R0, ret+8(FP)
RET
// func epollctl(epfd, op, fd int32, ev *epollEvent) int
TEXT runtime·epollctl(SB),NOSPLIT,$-8
MOVW epfd+0(FP), R0
MOVW op+4(FP), R1
MOVW fd+8(FP), R2
MOVD ev+16(FP), R3
MOVD $SYS_epoll_ctl, R8
SVC
MOVW R0, ret+24(FP)
RET
// int32 runtime·epollwait(int32 epfd, EpollEvent *ev, int32 nev, int32 timeout);
TEXT runtime·epollwait(SB),NOSPLIT,$-8
MOVW epfd+0(FP), R0
MOVD ev+8(FP), R1
MOVW nev+16(FP), R2
MOVW timeout+20(FP), R3
MOVD $0, R4
MOVD $SYS_epoll_pwait, R8
SVC
MOVW R0, ret+24(FP)
RET
// void runtime·closeonexec(int32 fd);
TEXT runtime·closeonexec(SB),NOSPLIT,$-8
MOVW fd+0(FP), R0 // fd
MOVD $2, R1 // F_SETFD
MOVD $1, R2 // FD_CLOEXEC
MOVD $SYS_fcntl, R8
SVC
RET
// int access(const char *name, int mode)
TEXT runtime·access(SB),NOSPLIT,$0-20
MOVD $AT_FDCWD, R0
MOVD name+0(FP), R1
MOVW mode+8(FP), R2
MOVD $SYS_faccessat, R8
SVC
MOVW R0, ret+16(FP)
RET
// int connect(int fd, const struct sockaddr *addr, socklen_t len)
TEXT runtime·connect(SB),NOSPLIT,$0-28
MOVW fd+0(FP), R0
MOVD addr+8(FP), R1
MOVW len+16(FP), R2
MOVD $SYS_connect, R8
SVC
MOVW R0, ret+24(FP)
RET
// int socket(int domain, int typ, int prot)
TEXT runtime·socket(SB),NOSPLIT,$0-20
MOVW domain+0(FP), R0
MOVW typ+4(FP), R1
MOVW prot+8(FP), R2
MOVD $SYS_socket, R8
SVC
MOVW R0, ret+16(FP)
RET
// func sbrk0() uintptr
TEXT runtime·sbrk0(SB),NOSPLIT,$0-8
// Implemented as brk(NULL).
MOVD $0, R0
MOVD $SYS_brk, R8
SVC
MOVD R0, ret+0(FP)
RET
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