amd64: use segment memory for thread-local storage
Returns R14 and R15 to the available register pool.
Plays more nicely with ELF ABI C code.
In particular, our signal handlers will no longer crash
when a signal arrives during execution of a cgo C call.
Fixes #720.
R=ken2, r
CC=golang-dev
https://golang.org/cl/1847051
diff --git a/src/cmd/6l/obj.c b/src/cmd/6l/obj.c
index 724f112..3b981a6 100644
--- a/src/cmd/6l/obj.c
+++ b/src/cmd/6l/obj.c
@@ -165,6 +165,11 @@
INITRND = 4096;
break;
case 6: /* apple MACH */
+ /*
+ * OS X system constant - offset from 0(GS) to our TLS.
+ * Explained in ../../libcgo/darwin_amd64.c.
+ */
+ tlsoffset = 0x8a0;
machoinit();
HEADR = MACHORESERVE;
if(INITRND == -1)
@@ -176,6 +181,13 @@
break;
case 7: /* elf64 executable */
case 9: /* freebsd */
+ /*
+ * ELF uses TLS offset negative from FS.
+ * Translate 0(FS) and 8(FS) into -16(FS) and -8(FS).
+ * Also known to ../../pkg/runtime/linux/amd64/sys.s
+ * and ../../libcgo/linux_amd64.s.
+ */
+ tlsoffset = -16;
elfinit();
HEADR = ELFRESERVE;
if(INITTEXT == -1)
@@ -434,6 +446,8 @@
adrgotype = zsym(pn, f, h);
s = a->sym;
t = a->type;
+ if(t == D_INDIR+D_GS)
+ a->offset += tlsoffset;
if(t != D_AUTO && t != D_PARAM) {
if(s && adrgotype)
s->gotype = adrgotype;
