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

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>

diff --git a/src/cmd/go/build.go b/src/cmd/go/build.go
index c29f6a78a0ee1ac8b3e93325430acba1aa822051..5cd92c23fa2f7c55fcad965ace82dabcdcc88c50 100644 (file)
--- a/src/cmd/go/build.go
+++ b/src/cmd/go/build.go
@@ -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

diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index 1dbd3d20944ff18a909f8482e58b3a898a32ac88..eb7b30a344d2c059bc350b078929baf9720427e5 100644 (file)
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -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

diff --git a/src/runtime/sys_linux_386.s b/src/runtime/sys_linux_386.s
index d26b25e987b7f4a18348b850d4c1fd6acf676f19..98626d14c854bba57aab2d350930ffd5d46c0777 100644 (file)
--- a/src/runtime/sys_linux_386.s
+++ b/src/runtime/sys_linux_386.s
@@ -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
 
@@ -227,9 +221,9 @@ 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
+       INT     $3      // not reached
        RET
 
 TEXT runtime·mmap(SB),NOSPLIT,$0
@@ -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