[PATCH] riscv: Implement TLS Descriptors
Luke Zhuang
luke.zhuang@linux.alibaba.com
Tue Jul 14 14:30:42 GMT 2026
From: "Luke Zhuang" <luke.zhuang@linux.alibaba.com>
Implement TLS Descriptors (TLSDESC) for RISC-V, as specified by the
RISC-V psABI TLSDESC extension [1].
This adds the RISC-V TLSDESC relocation handling and the three resolver
entry points used by the dynamic loader:
_dl_tlsdesc_undefweak
_dl_tlsdesc_return
_dl_tlsdesc_dynamic
The dynamic resolver implements the usual fast path by checking the DTV
generation counter, and falls back to __tls_get_addr on the slow path.
This work is based on Tatsuyuki Ishi's original patch series [2], and
is being relanded with his authorization. The reland includes the
following updates:
* Do not save and restore vector registers in _dl_tlsdesc_dynamic.
The RISC-V psABI now defines vector registers and vector CSRs as
caller-clobbered across TLSDESC calls [3], so preserving live vector
state is the compiler's responsibility.
* Call HIDDEN_JUMPTARGET(__tls_get_addr) from ld.so, avoiding a PLT
reference to __tls_get_addr.
* Publish TLSDESC entries in elf_machine_rela in arg-before-entry
order, and use a volatile tlsdesc pointer, matching the ordering
used by other architectures.
* Add sysdeps/riscv/tst-gnu2-tls2.h to test that the RISC-V TLSDESC
resolver preserves the required caller-saved GPR and FPR state
across the slow path.
Basic GCC and binutils support for RISC-V TLSDESC relocations is already
upstream [4][5]. Linker relaxation support is on the way but should not
be a blocker.
[1] https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/373
[2] https://inbox.sourceware.org/libc-alpha/09A14C77-9EEA-4707-9E36-D3AAF8A98B24@gmail.com/T/#u
[3] https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/496
[4] https://gcc.gnu.org/cgit/gcc/commit/?id=97069657c4e40b209c7b774e12faaca13812a86c
[5] https://sourceware.org/git/?p=binutils-gdb.git;a=commitdiff;h=159afbb7617d2c8a9cd3f3350374711f37f60442
Co-authored-by: Tatsuyuki Ishi <ishitatsuyuki@gmail.com>
Signed-off-by: Luke Zhuang <luke.zhuang@linux.alibaba.com>
---
sysdeps/riscv/Makefile | 10 ++
sysdeps/riscv/dl-lookupcfg.h | 27 +++++
sysdeps/riscv/dl-machine.h | 54 ++++++++-
sysdeps/riscv/dl-tlsdesc.S | 221 ++++++++++++++++++++++++++++++++++
sysdeps/riscv/dl-tlsdesc.h | 48 ++++++++
sysdeps/riscv/linkmap.h | 1 +
sysdeps/riscv/preconfigure | 1 +
sysdeps/riscv/tlsdesc.c | 38 ++++++
sysdeps/riscv/tlsdesc.sym | 19 +++
sysdeps/riscv/tst-gnu2-tls2.h | 201 +++++++++++++++++++++++++++++++
10 files changed, 619 insertions(+), 1 deletion(-)
create mode 100644 sysdeps/riscv/dl-lookupcfg.h
create mode 100644 sysdeps/riscv/dl-tlsdesc.S
create mode 100644 sysdeps/riscv/dl-tlsdesc.h
create mode 100644 sysdeps/riscv/tlsdesc.c
create mode 100644 sysdeps/riscv/tlsdesc.sym
create mode 100644 sysdeps/riscv/tst-gnu2-tls2.h
diff --git a/sysdeps/riscv/Makefile b/sysdeps/riscv/Makefile
index c08753ae8a..fc16081cde 100644
--- a/sysdeps/riscv/Makefile
+++ b/sysdeps/riscv/Makefile
@@ -4,6 +4,16 @@ endif
ifeq ($(subdir),elf)
gen-as-const-headers += dl-link.sym
+sysdep-dl-routines += \
+ dl-tlsdesc \
+ tlsdesc \
+ # routines
+endif
+
+ifeq ($(subdir),csu)
+gen-as-const-headers += \
+ tlsdesc.sym \
+ # gen-as-const-headers
endif
# RISC-V's assembler also needs to know about PIC as it changes the definition
diff --git a/sysdeps/riscv/dl-lookupcfg.h b/sysdeps/riscv/dl-lookupcfg.h
new file mode 100644
index 0000000000..414c8c8f8e
--- /dev/null
+++ b/sysdeps/riscv/dl-lookupcfg.h
@@ -0,0 +1,27 @@
+/* Configuration of lookup functions.
+ Copyright (C) 2026 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library. If not, see
+ <https://www.gnu.org/licenses/>. */
+
+#define DL_UNMAP_IS_SPECIAL
+
+#include_next <dl-lookupcfg.h>
+
+struct link_map;
+
+extern void _dl_unmap (struct link_map *map);
+
+#define DL_UNMAP(map) _dl_unmap (map)
diff --git a/sysdeps/riscv/dl-machine.h b/sysdeps/riscv/dl-machine.h
index babb52af20..79f0d02cab 100644
--- a/sysdeps/riscv/dl-machine.h
+++ b/sysdeps/riscv/dl-machine.h
@@ -25,6 +25,7 @@
#include <elf/elf.h>
#include <sys/asm.h>
#include <dl-tls.h>
+#include <dl-tlsdesc.h>
#include <dl-irel.h>
#include <dl-static-tls.h>
#include <dl-machine-rel.h>
@@ -51,7 +52,8 @@
|| (__WORDSIZE == 32 && (type) == R_RISCV_TLS_TPREL32) \
|| (__WORDSIZE == 64 && (type) == R_RISCV_TLS_DTPREL64) \
|| (__WORDSIZE == 64 && (type) == R_RISCV_TLS_DTPMOD64) \
- || (__WORDSIZE == 64 && (type) == R_RISCV_TLS_TPREL64))) \
+ || (__WORDSIZE == 64 && (type) == R_RISCV_TLS_TPREL64) \
+ || ((type) == R_RISCV_TLSDESC))) \
| (ELF_RTYPE_CLASS_COPY * ((type) == R_RISCV_COPY)))
/* Return nonzero iff ELF header is compatible with the running host. */
@@ -220,6 +222,37 @@ elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
}
break;
+ case R_RISCV_TLSDESC:
+ {
+ struct tlsdesc volatile *td =
+ (struct tlsdesc volatile *)reloc_addr;
+ if (!sym)
+ {
+ td->arg = (void *) reloc->r_addend;
+ td->entry = _dl_tlsdesc_undefweak;
+ }
+ else
+ {
+# ifndef SHARED
+ CHECK_STATIC_TLS (map, sym_map);
+# else
+ if (!TRY_STATIC_TLS (map, sym_map))
+ {
+ td->arg = _dl_make_tlsdesc_dynamic
+ (sym_map, sym->st_value + reloc->r_addend);
+ td->entry = _dl_tlsdesc_dynamic;
+ }
+ else
+# endif
+ {
+ td->arg
+ = (void *) (TLS_TPREL_VALUE (sym_map, sym) + reloc->r_addend);
+ td->entry = _dl_tlsdesc_return;
+ }
+ }
+ break;
+ }
+
case R_RISCV_COPY:
{
if (__glibc_unlikely (sym == NULL))
@@ -290,6 +323,25 @@ elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
else
*reloc_addr = map->l_mach.plt;
}
+ else if (__glibc_likely (r_type == R_RISCV_TLSDESC))
+ {
+ const Elf_Symndx symndx = ELFW (R_SYM) (reloc->r_info);
+ const ElfW (Sym) *symtab = (const void *)D_PTR (map, l_info[DT_SYMTAB]);
+ const ElfW (Sym) *sym = &symtab[symndx];
+ const struct r_found_version *version = NULL;
+
+ if (map->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
+ {
+ const ElfW (Half) *vernum =
+ (const void *)D_PTR (map, l_info[VERSYMIDX (DT_VERSYM)]);
+ version = &map->l_versions[vernum[symndx] & 0x7fff];
+ }
+
+ /* Always initialize TLS descriptors completely, because lazy
+ initialization requires synchronization at every TLS access. */
+ elf_machine_rela (map, scope, reloc, sym, version, reloc_addr,
+ skip_ifunc);
+ }
else if (__glibc_unlikely (r_type == R_RISCV_IRELATIVE))
{
ElfW(Addr) value = map->l_addr + reloc->r_addend;
diff --git a/sysdeps/riscv/dl-tlsdesc.S b/sysdeps/riscv/dl-tlsdesc.S
new file mode 100644
index 0000000000..b11bd25e62
--- /dev/null
+++ b/sysdeps/riscv/dl-tlsdesc.S
@@ -0,0 +1,221 @@
+/* Thread-local storage handling in the ELF dynamic linker.
+ RISC-V version.
+ Copyright (C) 2026 Free Software Foundation, Inc.
+
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <sysdep.h>
+#include <tls.h>
+#include <tlsdesc.h>
+
+/* The fast path does not call function and does not need to align sp, but
+ to simplify handling when going into the slow path, keep sp aligned all
+ the time.
+ */
+#define FRAME_SIZE_FAST (-((-3 * SZREG) & ALMASK))
+
+/* The slow path save slot layout, from lower address to higher address, is:
+ 1. 12 GP registers
+ 2. 20 FP registers
+
+ Besides a0 and t0, the vector registers are also caller-saved per the psABI
+ (riscv-non-isa/riscv-elf-psabi-doc#496) so they are not preserved across
+ the TLSDESC ifunc.
+ */
+#if defined(__riscv_float_abi_soft)
+# define FRAME_SIZE_SLOW (-((-12 * SZREG) & ALMASK))
+#else
+# define FRAME_SIZE_SLOW (-((-12 * SZREG - 20 * SZFREG) & ALMASK))
+#endif
+
+ .text
+
+ /* Compute the thread pointer offset for symbols in the static
+ TLS block. The offset is the same for all threads.
+ Prototype:
+ _dl_tlsdesc_return (tlsdesc *) ;
+ */
+ENTRY (_dl_tlsdesc_return)
+ REG_L a0, TLSDESC_ARG(a0)
+ jr t0
+END (_dl_tlsdesc_return)
+
+ /* Handler for undefined weak TLS symbols.
+ Prototype:
+ _dl_tlsdesc_undefweak (tlsdesc *);
+
+ The second word of the descriptor contains the addend.
+ Return the addend minus the thread pointer. This ensures
+ that when the caller adds on the thread pointer it gets back
+ the addend. */
+
+ENTRY (_dl_tlsdesc_undefweak)
+ REG_L a0, TLSDESC_ARG(a0)
+ sub a0, a0, tp
+ jr t0
+END (_dl_tlsdesc_undefweak)
+
+#ifdef SHARED
+ /* Handler for dynamic TLS symbols.
+ Prototype:
+ _dl_tlsdesc_dynamic (tlsdesc *) ;
+
+ The second word of the descriptor points to a
+ tlsdesc_dynamic_arg structure.
+
+ Returns the offset between the thread pointer and the
+ object referenced by the argument.
+
+ unsigned long
+ _dl_tlsdesc_dynamic (struct tlsdesc *tdp)
+ {
+ struct tlsdesc_dynamic_arg *td = tdp->arg;
+ dtv_t *dtv = *(dtv_t **)((char *)__thread_pointer + TCBHEAD_DTV);
+ if (__builtin_expect (td->gen_count <= dtv[0].counter
+ && (dtv[td->tlsinfo.ti_module].pointer.val
+ != TLS_DTV_UNALLOCATED),
+ 1))
+ return dtv[td->tlsinfo.ti_module].pointer.val
+ + td->tlsinfo.ti_offset
+ - __thread_pointer;
+
+ return __tls_get_addr (&td->tlsinfo) - __thread_pointer;
+ }
+ */
+
+ENTRY (_dl_tlsdesc_dynamic)
+ /* Save just enough registers to support fast path, if we fall
+ into slow path we will save additional registers. */
+ add sp, sp, -FRAME_SIZE_FAST
+ REG_S t0, 0*SZREG(sp)
+ REG_S t1, 1*SZREG(sp)
+ REG_S t2, 2*SZREG(sp)
+
+ /* t0 = dtv */
+ REG_L t0, TCBHEAD_DTV(tp)
+ /* a0 = tdp->arg */
+ REG_L a0, TLSDESC_ARG(a0)
+ /* t1 = td->gen_count */
+ REG_L t1, TLSDESC_GEN_COUNT(a0)
+ /* t2 = dtv[0].counter */
+ REG_L t2, DTV_COUNTER(t0)
+ bltu t2, t1, .Lslow
+ /* t1 = td->tlsinfo.ti_module */
+ REG_L t1, TLSDESC_MODID(a0)
+ slli t1, t1, PTRLOG + 1 /* sizeof(dtv_t) == sizeof(void*) * 2 */
+ add t1, t1, t0
+ /* t1 = dtv[td->tlsinfo.ti_module].pointer.val */
+ REG_L t1, 0(t1)
+ li t2, TLS_DTV_UNALLOCATED
+ beq t1, t2, .Lslow
+ /* t2 = td->tlsinfo.ti_offset */
+ REG_L t2, TLSDESC_MODOFF(a0)
+ add a0, t1, t2
+.Lret:
+ sub a0, a0, tp
+ REG_L t0, 0*SZREG(sp)
+ REG_L t1, 1*SZREG(sp)
+ REG_L t2, 2*SZREG(sp)
+ add sp, sp, FRAME_SIZE_FAST
+ jr t0
+.Lslow:
+ /* This is the slow path. We need to call __tls_get_addr() which
+ means we need to save and restore all the register that the
+ callee will trash. */
+
+ /* Save the remaining registers that we must treat as caller save. */
+ addi sp, sp, -FRAME_SIZE_SLOW
+ REG_S ra, 0*SZREG(sp)
+ REG_S a1, 1*SZREG(sp)
+ REG_S a2, 2*SZREG(sp)
+ REG_S a3, 3*SZREG(sp)
+ REG_S a4, 4*SZREG(sp)
+ REG_S a5, 5*SZREG(sp)
+ REG_S a6, 6*SZREG(sp)
+ REG_S a7, 7*SZREG(sp)
+ REG_S t3, 8*SZREG(sp)
+ REG_S t4, 9*SZREG(sp)
+ REG_S t5, 10*SZREG(sp)
+ REG_S t6, 11*SZREG(sp)
+
+#ifndef __riscv_float_abi_soft
+ FREG_S ft0, (12*SZREG + 0*SZFREG)(sp)
+ FREG_S ft1, (12*SZREG + 1*SZFREG)(sp)
+ FREG_S ft2, (12*SZREG + 2*SZFREG)(sp)
+ FREG_S ft3, (12*SZREG + 3*SZFREG)(sp)
+ FREG_S ft4, (12*SZREG + 4*SZFREG)(sp)
+ FREG_S ft5, (12*SZREG + 5*SZFREG)(sp)
+ FREG_S ft6, (12*SZREG + 6*SZFREG)(sp)
+ FREG_S ft7, (12*SZREG + 7*SZFREG)(sp)
+ FREG_S fa0, (12*SZREG + 8*SZFREG)(sp)
+ FREG_S fa1, (12*SZREG + 9*SZFREG)(sp)
+ FREG_S fa2, (12*SZREG + 10*SZFREG)(sp)
+ FREG_S fa3, (12*SZREG + 11*SZFREG)(sp)
+ FREG_S fa4, (12*SZREG + 12*SZFREG)(sp)
+ FREG_S fa5, (12*SZREG + 13*SZFREG)(sp)
+ FREG_S fa6, (12*SZREG + 14*SZFREG)(sp)
+ FREG_S fa7, (12*SZREG + 15*SZFREG)(sp)
+ FREG_S ft8, (12*SZREG + 16*SZFREG)(sp)
+ FREG_S ft9, (12*SZREG + 17*SZFREG)(sp)
+ FREG_S ft10, (12*SZREG + 18*SZFREG)(sp)
+ FREG_S ft11, (12*SZREG + 19*SZFREG)(sp)
+#endif
+
+ call HIDDEN_JUMPTARGET(__tls_get_addr)
+ addi a0, a0, -TLS_DTV_OFFSET
+
+ REG_L ra, 0*SZREG(sp)
+ REG_L a1, 1*SZREG(sp)
+ REG_L a2, 2*SZREG(sp)
+ REG_L a3, 3*SZREG(sp)
+ REG_L a4, 4*SZREG(sp)
+ REG_L a5, 5*SZREG(sp)
+ REG_L a6, 6*SZREG(sp)
+ REG_L a7, 7*SZREG(sp)
+ REG_L t3, 8*SZREG(sp)
+ REG_L t4, 9*SZREG(sp)
+ REG_L t5, 10*SZREG(sp)
+ REG_L t6, 11*SZREG(sp)
+
+#ifndef __riscv_float_abi_soft
+ FREG_L ft0, (12*SZREG + 0*SZFREG)(sp)
+ FREG_L ft1, (12*SZREG + 1*SZFREG)(sp)
+ FREG_L ft2, (12*SZREG + 2*SZFREG)(sp)
+ FREG_L ft3, (12*SZREG + 3*SZFREG)(sp)
+ FREG_L ft4, (12*SZREG + 4*SZFREG)(sp)
+ FREG_L ft5, (12*SZREG + 5*SZFREG)(sp)
+ FREG_L ft6, (12*SZREG + 6*SZFREG)(sp)
+ FREG_L ft7, (12*SZREG + 7*SZFREG)(sp)
+ FREG_L fa0, (12*SZREG + 8*SZFREG)(sp)
+ FREG_L fa1, (12*SZREG + 9*SZFREG)(sp)
+ FREG_L fa2, (12*SZREG + 10*SZFREG)(sp)
+ FREG_L fa3, (12*SZREG + 11*SZFREG)(sp)
+ FREG_L fa4, (12*SZREG + 12*SZFREG)(sp)
+ FREG_L fa5, (12*SZREG + 13*SZFREG)(sp)
+ FREG_L fa6, (12*SZREG + 14*SZFREG)(sp)
+ FREG_L fa7, (12*SZREG + 15*SZFREG)(sp)
+ FREG_L ft8, (12*SZREG + 16*SZFREG)(sp)
+ FREG_L ft9, (12*SZREG + 17*SZFREG)(sp)
+ FREG_L ft10, (12*SZREG + 18*SZFREG)(sp)
+ FREG_L ft11, (12*SZREG + 19*SZFREG)(sp)
+#endif
+
+ addi sp, sp, FRAME_SIZE_SLOW
+ j .Lret
+END (_dl_tlsdesc_dynamic)
+ .hidden HIDDEN_JUMPTARGET(__tls_get_addr)
+#endif
diff --git a/sysdeps/riscv/dl-tlsdesc.h b/sysdeps/riscv/dl-tlsdesc.h
new file mode 100644
index 0000000000..366b454183
--- /dev/null
+++ b/sysdeps/riscv/dl-tlsdesc.h
@@ -0,0 +1,48 @@
+/* Thread-local storage descriptor handling in the ELF dynamic linker.
+ RISC-V version.
+ Copyright (C) 2026 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library. If not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef _DL_TLSDESC_H
+# define _DL_TLSDESC_H 1
+
+#include <dl-tls.h>
+
+/* Type used to represent a TLS descriptor in the GOT. */
+struct tlsdesc
+{
+ unsigned long (*entry) (struct tlsdesc *);
+ void *arg;
+};
+
+/* Type used as the argument in a TLS descriptor for a symbol that
+ needs dynamic TLS offsets. */
+struct tlsdesc_dynamic_arg
+{
+ tls_index tlsinfo;
+ size_t gen_count;
+};
+
+extern unsigned long _dl_tlsdesc_return (struct tlsdesc *) attribute_hidden;
+extern unsigned long _dl_tlsdesc_undefweak (struct tlsdesc *) attribute_hidden;
+
+# ifdef SHARED
+extern void *_dl_make_tlsdesc_dynamic (struct link_map *, size_t);
+extern unsigned long _dl_tlsdesc_dynamic (struct tlsdesc *) attribute_hidden;
+# endif
+
+#endif /* _DL_TLSDESC_H */
diff --git a/sysdeps/riscv/linkmap.h b/sysdeps/riscv/linkmap.h
index ac170bb342..2fa3f6d43f 100644
--- a/sysdeps/riscv/linkmap.h
+++ b/sysdeps/riscv/linkmap.h
@@ -1,4 +1,5 @@
struct link_map_machine
{
ElfW(Addr) plt; /* Address of .plt. */
+ void *tlsdesc_table; /* Address of TLS descriptor hash table. */
};
diff --git a/sysdeps/riscv/preconfigure b/sysdeps/riscv/preconfigure
index 57fe6822cf..7c30cf045c 100755
--- a/sysdeps/riscv/preconfigure
+++ b/sysdeps/riscv/preconfigure
@@ -74,6 +74,7 @@ riscv*)
base_machine=riscv
machine=riscv/rv$xlen/$float_machine
+ mtls_descriptor=desc
printf "%s\n" "#define RISCV_ABI_XLEN $xlen" >>confdefs.h
diff --git a/sysdeps/riscv/tlsdesc.c b/sysdeps/riscv/tlsdesc.c
new file mode 100644
index 0000000000..f2cef3db77
--- /dev/null
+++ b/sysdeps/riscv/tlsdesc.c
@@ -0,0 +1,38 @@
+/* Manage TLS descriptors. RISC-V version.
+ Copyright (C) 2026 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <ldsodefs.h>
+#include <tls.h>
+#include <dl-tls.h>
+#include <dl-tlsdesc.h>
+#include <dl-unmap-segments.h>
+#include <tlsdeschtab.h>
+
+/* Unmap the dynamic object, but also release its TLS descriptor table
+ if there is one. */
+
+void
+_dl_unmap (struct link_map *map)
+{
+ _dl_unmap_segments (map);
+
+#ifdef SHARED
+ if (map->l_mach.tlsdesc_table)
+ htab_delete (map->l_mach.tlsdesc_table);
+#endif
+}
diff --git a/sysdeps/riscv/tlsdesc.sym b/sysdeps/riscv/tlsdesc.sym
new file mode 100644
index 0000000000..652e72ea58
--- /dev/null
+++ b/sysdeps/riscv/tlsdesc.sym
@@ -0,0 +1,19 @@
+#include <stddef.h>
+#include <sysdep.h>
+#include <tls.h>
+#include <link.h>
+#include <dl-tls.h>
+#include <dl-tlsdesc.h>
+
+--
+
+-- Abuse tls.h macros to derive offsets relative to the thread register.
+
+TLSDESC_ARG offsetof(struct tlsdesc, arg)
+TLSDESC_GEN_COUNT offsetof(struct tlsdesc_dynamic_arg, gen_count)
+TLSDESC_MODID offsetof(struct tlsdesc_dynamic_arg, tlsinfo.ti_module)
+TLSDESC_MODOFF offsetof(struct tlsdesc_dynamic_arg, tlsinfo.ti_offset)
+TCBHEAD_DTV offsetof(tcbhead_t, dtv) - sizeof(tcbhead_t) - TLS_TCB_OFFSET
+DTV_COUNTER offsetof(dtv_t, counter)
+TLS_DTV_UNALLOCATED TLS_DTV_UNALLOCATED
+TLS_DTV_OFFSET TLS_DTV_OFFSET
diff --git a/sysdeps/riscv/tst-gnu2-tls2.h b/sysdeps/riscv/tst-gnu2-tls2.h
new file mode 100644
index 0000000000..ef5b345ef2
--- /dev/null
+++ b/sysdeps/riscv/tst-gnu2-tls2.h
@@ -0,0 +1,201 @@
+/* Test TLSDESC relocation. RISC-V version.
+ Copyright (C) 2026 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+/* The TLSDESC calling convention requires _dl_tlsdesc_dynamic to preserve
+ every register except a0 (the argument/return value) and t0 (the return
+ address). On the slow path it calls __tls_get_addr, an ordinary function
+ that may clobber all caller-saved registers, so the resolver must save and
+ restore the caller-saved general-purpose registers a1-a7 and t1-t6, and
+ the 20 caller-saved floating-point registers (ft0-ft7, fa0-fa7, ft8-ft11),
+ around that call. Load sentinel values into them before the TLS access and
+ verify that they are unchanged afterwards.
+
+ Vector registers and vector CSRs are intentionally *not* checked: per the
+ RISC-V psABI they are clobbered by the TLSDESC call (see
+ riscv-non-isa/riscv-elf-psabi-doc#496), so the compiler, not the dynamic
+ linker, is responsible for preserving them across the access. */
+
+#define INIT_TLSDESC_CALL() \
+ register unsigned long tlsdesc_gp_a1 asm ("a1") = 11; \
+ register unsigned long tlsdesc_gp_a2 asm ("a2") = 12; \
+ register unsigned long tlsdesc_gp_a3 asm ("a3") = 13; \
+ register unsigned long tlsdesc_gp_a4 asm ("a4") = 14; \
+ register unsigned long tlsdesc_gp_a5 asm ("a5") = 15; \
+ register unsigned long tlsdesc_gp_a6 asm ("a6") = 16; \
+ register unsigned long tlsdesc_gp_a7 asm ("a7") = 17; \
+ register unsigned long tlsdesc_gp_t1 asm ("t1") = 21; \
+ register unsigned long tlsdesc_gp_t2 asm ("t2") = 22; \
+ register unsigned long tlsdesc_gp_t3 asm ("t3") = 23; \
+ register unsigned long tlsdesc_gp_t4 asm ("t4") = 24; \
+ register unsigned long tlsdesc_gp_t5 asm ("t5") = 25; \
+ register unsigned long tlsdesc_gp_t6 asm ("t6") = 26;
+
+#define LOAD_REGISTER_GP() \
+ asm volatile ("" \
+ : "+r" (tlsdesc_gp_a1), "+r" (tlsdesc_gp_a2), \
+ "+r" (tlsdesc_gp_a3), "+r" (tlsdesc_gp_a4), \
+ "+r" (tlsdesc_gp_a5), "+r" (tlsdesc_gp_a6), \
+ "+r" (tlsdesc_gp_a7), "+r" (tlsdesc_gp_t1), \
+ "+r" (tlsdesc_gp_t2), "+r" (tlsdesc_gp_t3), \
+ "+r" (tlsdesc_gp_t4), "+r" (tlsdesc_gp_t5), \
+ "+r" (tlsdesc_gp_t6) \
+ : \
+ : "memory")
+
+#define SAVE_REGISTER_GP() \
+ LOAD_REGISTER_GP (); \
+ if (tlsdesc_gp_a1 != 11 || tlsdesc_gp_a2 != 12 \
+ || tlsdesc_gp_a3 != 13 || tlsdesc_gp_a4 != 14 \
+ || tlsdesc_gp_a5 != 15 || tlsdesc_gp_a6 != 16 \
+ || tlsdesc_gp_a7 != 17 || tlsdesc_gp_t1 != 21 \
+ || tlsdesc_gp_t2 != 22 || tlsdesc_gp_t3 != 23 \
+ || tlsdesc_gp_t4 != 24 || tlsdesc_gp_t5 != 25 \
+ || tlsdesc_gp_t6 != 26) \
+ { \
+ printf ("GP registers compare failed!\n"); \
+ abort (); \
+ }
+
+#define CLOBBER_REGISTER_GP() \
+ asm volatile ("li a1, 101" ::: "a1"); \
+ asm volatile ("li a2, 102" ::: "a2"); \
+ asm volatile ("li a3, 103" ::: "a3"); \
+ asm volatile ("li a4, 104" ::: "a4"); \
+ asm volatile ("li a5, 105" ::: "a5"); \
+ asm volatile ("li a6, 106" ::: "a6"); \
+ asm volatile ("li a7, 107" ::: "a7"); \
+ asm volatile ("li t1, 111" ::: "t1"); \
+ asm volatile ("li t2, 112" ::: "t2"); \
+ asm volatile ("li t3, 113" ::: "t3"); \
+ asm volatile ("li t4, 114" ::: "t4"); \
+ asm volatile ("li t5, 115" ::: "t5"); \
+ asm volatile ("li t6, 116" ::: "t6")
+
+#ifndef __riscv_float_abi_soft
+
+# define LOAD_REGISTER_FLOAT() \
+ double src_float[20]; \
+ for (int i = 0; i < 20; i++) \
+ src_float[i] = i + 1; \
+ asm volatile ("fld ft0, %0" :: "m" (src_float[0]) : "ft0"); \
+ asm volatile ("fld ft1, %0" :: "m" (src_float[1]) : "ft1"); \
+ asm volatile ("fld ft2, %0" :: "m" (src_float[2]) : "ft2"); \
+ asm volatile ("fld ft3, %0" :: "m" (src_float[3]) : "ft3"); \
+ asm volatile ("fld ft4, %0" :: "m" (src_float[4]) : "ft4"); \
+ asm volatile ("fld ft5, %0" :: "m" (src_float[5]) : "ft5"); \
+ asm volatile ("fld ft6, %0" :: "m" (src_float[6]) : "ft6"); \
+ asm volatile ("fld ft7, %0" :: "m" (src_float[7]) : "ft7"); \
+ asm volatile ("fld fa0, %0" :: "m" (src_float[8]) : "fa0"); \
+ asm volatile ("fld fa1, %0" :: "m" (src_float[9]) : "fa1"); \
+ asm volatile ("fld fa2, %0" :: "m" (src_float[10]) : "fa2"); \
+ asm volatile ("fld fa3, %0" :: "m" (src_float[11]) : "fa3"); \
+ asm volatile ("fld fa4, %0" :: "m" (src_float[12]) : "fa4"); \
+ asm volatile ("fld fa5, %0" :: "m" (src_float[13]) : "fa5"); \
+ asm volatile ("fld fa6, %0" :: "m" (src_float[14]) : "fa6"); \
+ asm volatile ("fld fa7, %0" :: "m" (src_float[15]) : "fa7"); \
+ asm volatile ("fld ft8, %0" :: "m" (src_float[16]) : "ft8"); \
+ asm volatile ("fld ft9, %0" :: "m" (src_float[17]) : "ft9"); \
+ asm volatile ("fld ft10, %0" :: "m" (src_float[18]) : "ft10"); \
+ asm volatile ("fld ft11, %0" :: "m" (src_float[19]) : "ft11");
+
+# define SAVE_REGISTER_FLOAT() \
+ double restore_float[20]; \
+ asm volatile ("fsd ft0, %0" : "=m" (restore_float[0])); \
+ asm volatile ("fsd ft1, %0" : "=m" (restore_float[1])); \
+ asm volatile ("fsd ft2, %0" : "=m" (restore_float[2])); \
+ asm volatile ("fsd ft3, %0" : "=m" (restore_float[3])); \
+ asm volatile ("fsd ft4, %0" : "=m" (restore_float[4])); \
+ asm volatile ("fsd ft5, %0" : "=m" (restore_float[5])); \
+ asm volatile ("fsd ft6, %0" : "=m" (restore_float[6])); \
+ asm volatile ("fsd ft7, %0" : "=m" (restore_float[7])); \
+ asm volatile ("fsd fa0, %0" : "=m" (restore_float[8])); \
+ asm volatile ("fsd fa1, %0" : "=m" (restore_float[9])); \
+ asm volatile ("fsd fa2, %0" : "=m" (restore_float[10])); \
+ asm volatile ("fsd fa3, %0" : "=m" (restore_float[11])); \
+ asm volatile ("fsd fa4, %0" : "=m" (restore_float[12])); \
+ asm volatile ("fsd fa5, %0" : "=m" (restore_float[13])); \
+ asm volatile ("fsd fa6, %0" : "=m" (restore_float[14])); \
+ asm volatile ("fsd fa7, %0" : "=m" (restore_float[15])); \
+ asm volatile ("fsd ft8, %0" : "=m" (restore_float[16])); \
+ asm volatile ("fsd ft9, %0" : "=m" (restore_float[17])); \
+ asm volatile ("fsd ft10, %0" : "=m" (restore_float[18])); \
+ asm volatile ("fsd ft11, %0" : "=m" (restore_float[19])); \
+ if (memcmp (src_float, restore_float, sizeof (src_float)) != 0) \
+ { \
+ printf ("Float registers compare failed!\n"); \
+ abort (); \
+ }
+
+/* Clobber the caller-saved floating-point registers inside malloc, which is
+ reached through __tls_get_addr on the TLSDESC slow path. If the resolver
+ fails to save and restore them, the sentinels planted by
+ BEFORE_TLSDESC_CALL will be corrupted and AFTER_TLSDESC_CALL will abort. */
+# define PREPARE_MALLOC() \
+{ \
+ static const double clobber_float[20] = \
+ { 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, \
+ 111, 112, 113, 114, 115, 116, 117, 118, 119, 120 }; \
+ CLOBBER_REGISTER_GP (); \
+ asm volatile ("fld ft0, %0" :: "m" (clobber_float[0]) : "ft0"); \
+ asm volatile ("fld ft1, %0" :: "m" (clobber_float[1]) : "ft1"); \
+ asm volatile ("fld ft2, %0" :: "m" (clobber_float[2]) : "ft2"); \
+ asm volatile ("fld ft3, %0" :: "m" (clobber_float[3]) : "ft3"); \
+ asm volatile ("fld ft4, %0" :: "m" (clobber_float[4]) : "ft4"); \
+ asm volatile ("fld ft5, %0" :: "m" (clobber_float[5]) : "ft5"); \
+ asm volatile ("fld ft6, %0" :: "m" (clobber_float[6]) : "ft6"); \
+ asm volatile ("fld ft7, %0" :: "m" (clobber_float[7]) : "ft7"); \
+ asm volatile ("fld fa0, %0" :: "m" (clobber_float[8]) : "fa0"); \
+ asm volatile ("fld fa1, %0" :: "m" (clobber_float[9]) : "fa1"); \
+ asm volatile ("fld fa2, %0" :: "m" (clobber_float[10]) : "fa2"); \
+ asm volatile ("fld fa3, %0" :: "m" (clobber_float[11]) : "fa3"); \
+ asm volatile ("fld fa4, %0" :: "m" (clobber_float[12]) : "fa4"); \
+ asm volatile ("fld fa5, %0" :: "m" (clobber_float[13]) : "fa5"); \
+ asm volatile ("fld fa6, %0" :: "m" (clobber_float[14]) : "fa6"); \
+ asm volatile ("fld fa7, %0" :: "m" (clobber_float[15]) : "fa7"); \
+ asm volatile ("fld ft8, %0" :: "m" (clobber_float[16]) : "ft8"); \
+ asm volatile ("fld ft9, %0" :: "m" (clobber_float[17]) : "ft9"); \
+ asm volatile ("fld ft10, %0" :: "m" (clobber_float[18]) : "ft10"); \
+ asm volatile ("fld ft11, %0" :: "m" (clobber_float[19]) : "ft11"); \
+}
+
+# define BEFORE_TLSDESC_CALL() \
+ LOAD_REGISTER_GP (); \
+ LOAD_REGISTER_FLOAT ()
+
+# define AFTER_TLSDESC_CALL() \
+ SAVE_REGISTER_GP (); \
+ SAVE_REGISTER_FLOAT ()
+
+#else /* __riscv_float_abi_soft */
+
+# define PREPARE_MALLOC() \
+ CLOBBER_REGISTER_GP ()
+
+# define BEFORE_TLSDESC_CALL() \
+ LOAD_REGISTER_GP ()
+
+# define AFTER_TLSDESC_CALL() \
+ SAVE_REGISTER_GP ()
+
+#endif /* __riscv_float_abi_soft */
+
+#include_next <tst-gnu2-tls2.h>
--
2.47.1
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