Hi,
I think there's a bug in musl's TLSDESC implementation for ARM32.
TLSDESC uses two consecutive GOT slots to store a function pointer and its argument. Usually, the function pointer is stored in the first slot and the argument in the second. However, on ARM32, the order is reversed; the argument is stored in the first slot.
If a TLSDESC relocation has a non-zero addend, it's applied to the function argument and not to the function pointer. That means, for an ABI that uses the REL-type relocations (as opposed to RELA-type), the addend should be stored to the location where the function argument is stored, and that's the first slot on ARM32.
So, I believe we need something like this.
diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index ceca3c98..254fa5b8 100644
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c
@@ -513,11 +513,17 @@ static void do_relocs(struct dso *dso, size_t *rel, size_t rel_size, size_t stri
case REL_TPOFF_NEG:
*reloc_addr = def.dso->tls.offset - tls_val + addend;
break;
#endif
case REL_TLSDESC:
- if (stride<3) addend = reloc_addr[1];
+ if (stride<3) {
+#ifdef TLSDESC_BACKWARDS
+ addend = reloc_addr[0];
+#else
+ addend = reloc_addr[1];
+#endif
+ }
if (def.dso->tls_id > static_tls_cnt) {
struct td_index *new = malloc(sizeof *new);
if (!new) {
error(
"Error relocating %s: cannot allocate TLSDESC for %s",