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cmd/go, runtime: always use position-independent code to invoke vsyscall helper on linux/386

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golang.org/cl/16346 changed the runtime on linux/386 to invoke the vsyscall
helper via a PIC sequence (CALL 0x10(GS)) when dynamically linking. But it's
actually quite easy to make that code sequence work all the time, so do that,
and remove the ugly machinery that passed the buildmode from the go tool to the
assembly.

This means enlarging m.tls so that we can safely access 0x10(GS) (GS is set to
&m.tls + 4, so 0x10(GS) accesses m_tls[5]).

Change-Id: I1345c34029b149cb5f25320bf19a3cdd73a056fa
Reviewed-on: https://go-review.googlesource.com/16796
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Michael Hudson-Doyle 2015-11-12 12:55:57 +13:00
parent 52393ad036
commit 7af0839e11
3 changed files with 49 additions and 52 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
src/cmd/go/build.go
View File

@ -332,9 +332,6 @@ func buildModeInit() {
_, gccgo := buildToolchain.(gccgoToolchain)
var codegenArg string
platform := goos + "/" + goarch
if buildBuildmode != "default" {
buildAsmflags = append(buildAsmflags, "-D=GOBUILDMODE_"+strings.Replace(buildBuildmode, "-", "_", -1)+"=1")
}
switch buildBuildmode {
case "archive":
pkgsFilter = pkgsNotMain

2
src/runtime/runtime2.go
View File

@ -274,7 +274,7 @@ type m struct {
procid uint64 // for debuggers, but offset not hard-coded
gsignal *g // signal-handling g
sigmask [4]uintptr // storage for saved signal mask
tls [4]uintptr // thread-local storage (for x86 extern register)
tls [6]uintptr // thread-local storage (for x86 extern register)
mstartfn func()
curg *g // current running goroutine
caughtsig guintptr // goroutine running during fatal signal

94
src/runtime/sys_linux_386.s
View File

@ -10,23 +10,17 @@
#include "go_tls.h"
#include "textflag.h"
#ifdef GOBUILDMODE_shared
#define INVOKE_SYSINFO CALL 0x10(GS)
#else
#define INVOKE_SYSINFO CALL *runtime·_vdso(SB)
#endif
TEXT runtime·exit(SB),NOSPLIT,$0
MOVL $252, AX // syscall number
MOVL code+0(FP), BX
INVOKE_SYSINFO
CALL 0x10(GS)
INT $3 // not reached
RET
TEXT runtime·exit1(SB),NOSPLIT,$0
MOVL $1, AX // exit - exit the current os thread
MOVL code+0(FP), BX
INVOKE_SYSINFO
CALL 0x10(GS)
INT $3 // not reached
RET
@ -35,7 +29,7 @@ TEXT runtime·open(SB),NOSPLIT,$0
MOVL name+0(FP), BX
MOVL mode+4(FP), CX
MOVL perm+8(FP), DX
INVOKE_SYSINFO
CALL 0x10(GS)
CMPL AX, $0xfffff001
JLS 2(PC)
MOVL $-1, AX
@ -45,7 +39,7 @@ TEXT runtime·open(SB),NOSPLIT,$0
TEXT runtime·closefd(SB),NOSPLIT,$0
MOVL $6, AX // syscall - close
MOVL fd+0(FP), BX
INVOKE_SYSINFO
CALL 0x10(GS)
CMPL AX, $0xfffff001
JLS 2(PC)
MOVL $-1, AX
@ -57,7 +51,7 @@ TEXT runtime·write(SB),NOSPLIT,$0
MOVL fd+0(FP), BX
MOVL p+4(FP), CX
MOVL n+8(FP), DX
INVOKE_SYSINFO
CALL 0x10(GS)
CMPL AX, $0xfffff001
JLS 2(PC)
MOVL $-1, AX
@ -69,7 +63,7 @@ TEXT runtime·read(SB),NOSPLIT,$0
MOVL fd+0(FP), BX
MOVL p+4(FP), CX
MOVL n+8(FP), DX
INVOKE_SYSINFO
CALL 0x10(GS)
CMPL AX, $0xfffff001
JLS 2(PC)
MOVL $-1, AX
@ -80,7 +74,7 @@ TEXT runtime·getrlimit(SB),NOSPLIT,$0
MOVL $191, AX // syscall - ugetrlimit
MOVL kind+0(FP), BX
MOVL limit+4(FP), CX
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL AX, ret+8(FP)
RET
@ -99,31 +93,31 @@ TEXT runtime·usleep(SB),NOSPLIT,$8
MOVL $0, DX
MOVL $0, SI
LEAL 0(SP), DI
INVOKE_SYSINFO
CALL 0x10(GS)
RET
TEXT runtime·gettid(SB),NOSPLIT,$0-4
MOVL $224, AX // syscall - gettid
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL AX, ret+0(FP)
RET
TEXT runtime·raise(SB),NOSPLIT,$12
MOVL $224, AX // syscall - gettid
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL AX, BX // arg 1 tid
MOVL sig+0(FP), CX // arg 2 signal
MOVL $238, AX // syscall - tkill
INVOKE_SYSINFO
CALL 0x10(GS)
RET
TEXT runtime·raiseproc(SB),NOSPLIT,$12
MOVL $20, AX // syscall - getpid
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL AX, BX // arg 1 pid
MOVL sig+0(FP), CX // arg 2 signal
MOVL $37, AX // syscall - kill
INVOKE_SYSINFO
CALL 0x10(GS)
RET
TEXT runtime·setitimer(SB),NOSPLIT,$0-12
@ -131,7 +125,7 @@ TEXT runtime·setitimer(SB),NOSPLIT,$0-12
MOVL mode+0(FP), BX
MOVL new+4(FP), CX
MOVL old+8(FP), DX
INVOKE_SYSINFO
CALL 0x10(GS)
RET
TEXT runtime·mincore(SB),NOSPLIT,$0-16
@ -139,7 +133,7 @@ TEXT runtime·mincore(SB),NOSPLIT,$0-16
MOVL addr+0(FP), BX
MOVL n+4(FP), CX
MOVL dst+8(FP), DX
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL AX, ret+12(FP)
RET
@ -149,7 +143,7 @@ TEXT time·now(SB), NOSPLIT, $32
MOVL $0, BX // CLOCK_REALTIME
LEAL 8(SP), CX
MOVL $0, DX
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL 8(SP), AX // sec
MOVL 12(SP), BX // nsec
@ -166,7 +160,7 @@ TEXT runtime·nanotime(SB), NOSPLIT, $32
MOVL $1, BX // CLOCK_MONOTONIC
LEAL 8(SP), CX
MOVL $0, DX
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL 8(SP), AX // sec
MOVL 12(SP), BX // nsec
@ -187,7 +181,7 @@ TEXT runtime·rtsigprocmask(SB),NOSPLIT,$0
MOVL new+4(FP), CX
MOVL old+8(FP), DX
MOVL size+12(FP), SI
INVOKE_SYSINFO
CALL 0x10(GS)
CMPL AX, $0xfffff001
JLS 2(PC)
INT $3
@ -199,7 +193,7 @@ TEXT runtime·rt_sigaction(SB),NOSPLIT,$0
MOVL new+4(FP), CX
MOVL old+8(FP), DX
MOVL size+12(FP), SI
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL AX, ret+16(FP)
RET
@ -227,7 +221,7 @@ TEXT runtime·sigtramp(SB),NOSPLIT,$12
TEXT runtime·sigreturn(SB),NOSPLIT,$0
MOVL $173, AX // rt_sigreturn
// Sigreturn expects same SP as signal handler,
// so cannot CALL *runtime._vsdo(SB) here.
// so cannot CALL 0x10(GS) here.
INT $0x80
INT $3 // not reached
RET
@ -241,7 +235,7 @@ TEXT runtime·mmap(SB),NOSPLIT,$0
MOVL fd+16(FP), DI
MOVL off+20(FP), BP
SHRL $12, BP
INVOKE_SYSINFO
CALL 0x10(GS)
CMPL AX, $0xfffff001
JLS 3(PC)
NOTL AX
@ -253,7 +247,7 @@ TEXT runtime·munmap(SB),NOSPLIT,$0
MOVL $91, AX // munmap
MOVL addr+0(FP), BX
MOVL n+4(FP), CX
INVOKE_SYSINFO
CALL 0x10(GS)
CMPL AX, $0xfffff001
JLS 2(PC)
INT $3
@ -264,7 +258,7 @@ TEXT runtime·madvise(SB),NOSPLIT,$0
MOVL addr+0(FP), BX
MOVL n+4(FP), CX
MOVL flags+8(FP), DX
INVOKE_SYSINFO
CALL 0x10(GS)
// ignore failure - maybe pages are locked
RET
@ -278,7 +272,7 @@ TEXT runtime·futex(SB),NOSPLIT,$0
MOVL ts+12(FP), SI
MOVL addr2+16(FP), DI
MOVL val3+20(FP), BP
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL AX, ret+24(FP)
RET
@ -300,10 +294,9 @@ TEXT runtime·clone(SB),NOSPLIT,$0
MOVL SI, 8(CX)
MOVL $1234, 12(CX)
// cannot use CALL *runtime·_vdso(SB) here, because
// the stack changes during the system call (after
// CALL *runtime·_vdso(SB), the child is still using
// the parent's stack when executing its RET instruction).
// cannot use CALL 0x10(GS) here, because the stack changes during the
// system call (after CALL 0x10(GS), the child is still using the
// parent's stack when executing its RET instruction).
INT $0x80
// In parent, return.
@ -320,7 +313,7 @@ TEXT runtime·clone(SB),NOSPLIT,$0
// Initialize AX to Linux tid
MOVL $224, AX
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL 0(SP), BX // m
MOVL 4(SP), DX // g
@ -371,7 +364,7 @@ TEXT runtime·sigaltstack(SB),NOSPLIT,$-8
MOVL $186, AX // sigaltstack
MOVL new+4(SP), BX
MOVL old+8(SP), CX
INVOKE_SYSINFO
CALL 0x10(GS)
CMPL AX, $0xfffff001
JLS 2(PC)
INT $3
@ -429,6 +422,12 @@ TEXT runtime·setldt(SB),NOSPLIT,$32
ADDL $0x4, CX // address
MOVL CX, 0(CX)
#endif
// We copy the dynamic linker behaviour of storing the vsyscall entry point
// at 0x10(GS) so that it can be invoked by "CALL 0x10(GS)" in all
// situations, not only those where the binary is actually dynamically
// linked.
MOVL runtime·_vdso(SB), AX
MOVL AX, 0x10(CX)
// set up user_desc
LEAL 16(SP), AX // struct user_desc
@ -442,7 +441,8 @@ TEXT runtime·setldt(SB),NOSPLIT,$32
MOVL AX, CX // user_desc
MOVL $16, DX // sizeof(user_desc)
MOVL $123, AX // syscall - modify_ldt
INVOKE_SYSINFO
// We can't call this via 0x10(GS) because this is called from setldt0 to set that up.
INT $0x80
// breakpoint on error
CMPL AX, $0xfffff001
@ -459,7 +459,7 @@ TEXT runtime·setldt(SB),NOSPLIT,$32
TEXT runtime·osyield(SB),NOSPLIT,$0
MOVL $158, AX
INVOKE_SYSINFO
CALL 0x10(GS)
RET
TEXT runtime·sched_getaffinity(SB),NOSPLIT,$0
@ -467,7 +467,7 @@ TEXT runtime·sched_getaffinity(SB),NOSPLIT,$0
MOVL pid+0(FP), BX
MOVL len+4(FP), CX
MOVL buf+8(FP), DX
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL AX, ret+12(FP)
RET
@ -475,7 +475,7 @@ TEXT runtime·sched_getaffinity(SB),NOSPLIT,$0
TEXT runtime·epollcreate(SB),NOSPLIT,$0
MOVL $254, AX
MOVL size+0(FP), BX
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL AX, ret+4(FP)
RET
@ -483,7 +483,7 @@ TEXT runtime·epollcreate(SB),NOSPLIT,$0
TEXT runtime·epollcreate1(SB),NOSPLIT,$0
MOVL $329, AX
MOVL flags+0(FP), BX
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL AX, ret+4(FP)
RET
@ -494,7 +494,7 @@ TEXT runtime·epollctl(SB),NOSPLIT,$0
MOVL op+4(FP), CX
MOVL fd+8(FP), DX
MOVL ev+12(FP), SI
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL AX, ret+16(FP)
RET
@ -505,7 +505,7 @@ TEXT runtime·epollwait(SB),NOSPLIT,$0
MOVL ev+4(FP), CX
MOVL nev+8(FP), DX
MOVL timeout+12(FP), SI
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL AX, ret+16(FP)
RET
@ -515,7 +515,7 @@ TEXT runtime·closeonexec(SB),NOSPLIT,$0
MOVL fd+0(FP), BX // fd
MOVL $2, CX // F_SETFD
MOVL $1, DX // FD_CLOEXEC
INVOKE_SYSINFO
CALL 0x10(GS)
RET
// int access(const char *name, int mode)
@ -523,7 +523,7 @@ TEXT runtime·access(SB),NOSPLIT,$0
MOVL $33, AX // syscall - access
MOVL name+0(FP), BX
MOVL mode+4(FP), CX
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL AX, ret+8(FP)
RET
@ -534,7 +534,7 @@ TEXT runtime·connect(SB),NOSPLIT,$0-16
MOVL $102, AX // syscall - socketcall
MOVL $3, BX // connect
LEAL fd+0(FP), CX
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL AX, ret+12(FP)
RET
@ -545,6 +545,6 @@ TEXT runtime·socket(SB),NOSPLIT,$0-16
MOVL $102, AX // syscall - socketcall
MOVL $1, BX // socket
LEAL domain+0(FP), CX
INVOKE_SYSINFO
CALL 0x10(GS)
MOVL AX, ret+12(FP)
RET