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Message-ID: <20260618191256.GQ3520958@port70.net>
Date: Thu, 18 Jun 2026 21:12:56 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: [PATCH] or1k: fix local-exec tls with large alignment
or1k uses an unusual variant of the TLS_ABOVE_TP layout:
powerpc, mips, m68k:
pthread | tls
+----------+-----------------+--
| |< tpoff >|
self a = e = m tp
arm, aarch64, sh:
pthread < gap >| tls
+----------+-------------+------
| | |
self a = e = tp m
or1k:
pthread < gap >| tls
+----------+-------------+------
| |< tpoff >|
self a = e m = tp
tp: thread pointer
a: address aligned to tls_align
e: end of the libc internal pthread self struct
m: min user tls address
the layout variant only matters for local-exec tls access, but then
ld and libc have to match how tp-relative tls addresses are computed.
or1k is tpoff=gap=16 in bfd ld, but it was gap=tpoff=0 in musl. this
works if tls_align <= 16, but an exe with larger tls_align fails.
TP_OFFSET (tpoff) and GAP_ABOVE_TP (gap) are now defined as
tpoff: tp - a
gap: m - a (so it is not really "gap above tp")
TPOFF_K = -tpoff is needed for relocs as the tls_module->offset is
internally computed relative to a, not tp.
this changes tp - e on or1k which in general may affect internal abi
(e.g. tlsdesc asm uses self->dtv) or toolchain abi (the layout below
m is not visible to the elf abi, but e.g. ssp uses self->canary on
some targets with fixed tp offset), but or1k seems unaffected. it is
possible to place the pthread struct such that tp = m = e on or1k,
to aviod this abi change, but that looks uglier (e.g. a != e then).
found and tested on user qemu-or1k.
---
arch/or1k/pthread_arch.h | 3 ++-
arch/or1k/reloc.h | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/or1k/pthread_arch.h b/arch/or1k/pthread_arch.h
index f75ea7e4..97197c8e 100644
--- a/arch/or1k/pthread_arch.h
+++ b/arch/or1k/pthread_arch.h
@@ -11,6 +11,7 @@ static inline uintptr_t __get_tp()
}
#define TLS_ABOVE_TP
-#define GAP_ABOVE_TP 0
+#define GAP_ABOVE_TP 16
+#define TP_OFFSET 16
#define MC_PC regs.pc
diff --git a/arch/or1k/reloc.h b/arch/or1k/reloc.h
index 128089ca..20d407b6 100644
--- a/arch/or1k/reloc.h
+++ b/arch/or1k/reloc.h
@@ -1,6 +1,6 @@
#define LDSO_ARCH "or1k"
-#define TPOFF_K 0
+#define TPOFF_K (-16)
#define REL_SYMBOLIC R_OR1K_32
#define REL_GOT R_OR1K_GLOB_DAT
--
2.52.0
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