fix TLS layout of TLS variant I when there is a gap above TP

In TLS variant I the TLS is above TP (or above a fixed offset from TP)
but on some targets there is a reserved gap above TP before TLS starts.

This matters for the local-exec tls access model when the offsets of
TLS variables from the TP are hard coded by the linker into the
executable, so the libc must compute these offsets the same way as the
linker.  The tls offset of the main module has to be

	alignup(GAP_ABOVE_TP, main_tls_align).

If there is no TLS in the main module then the gap can be ignored
since musl does not use it and the tls access models of shared
libraries are not affected.

The previous setup only worked if (tls_align & -GAP_ABOVE_TP) == 0
(i.e. TLS did not require large alignment) because the gap was
treated as a fixed offset from TP.  Now the TP points at the end
of the pthread struct (which is aligned) and there is a gap above
it (which may also need alignment).

The fix required changing TP_ADJ and __pthread_self on affected
targets (aarch64, arm and sh) and in the tlsdesc asm the offset to
access the dtv changed too.

1 files changed, 2 insertions, 3 deletions

diff --git a/src/ldso/aarch64/tlsdesc.s b/src/ldso/aarch64/tlsdesc.s
index 8ed5c267..8e4004d7 100644
--- a/src/ldso/aarch64/tlsdesc.s
+++ b/src/ldso/aarch64/tlsdesc.s
@@ -14,7 +14,7 @@ __tlsdesc_static:
 // size_t __tlsdesc_dynamic(size_t *a)
 // {
 // 	struct {size_t modidx,off;} *p = (void*)a[1];
-// 	size_t *dtv = *(size_t**)(tp + 16 - 8);
+// 	size_t *dtv = *(size_t**)(tp - 8);
 // 	if (p->modidx <= dtv[0])
 // 		return dtv[p->modidx] + p->off - tp;
 // 	return __tls_get_new(p) - tp;
@@ -28,8 +28,7 @@ __tlsdesc_dynamic:
 	mrs x1,tpidr_el0      // tp
 	ldr x0,[x0,#8]        // p
 	ldr x2,[x0]           // p->modidx
-	add x3,x1,#8
-	ldr x3,[x3]           // dtv
+	ldr x3,[x1,#-8]       // dtv
 	ldr x4,[x3]           // dtv[0]
 	cmp x2,x4
 	b.hi 1f