[v4,3/3] RISC-V: Implement TLS Descriptors.

diff --git a/sysdeps/riscv/Makefile b/sysdeps/riscv/Makefile
index 8fb10b164f..0fa1664cb1 100644
--- a/sysdeps/riscv/Makefile
+++ b/sysdeps/riscv/Makefile
@@ -2,6 +2,19 @@  ifeq ($(subdir),misc)
 sysdep_headers += sys/asm.h
 endif
 
+ifeq ($(subdir),elf)
+sysdep-dl-routines += \
+  dl-tlsdesc \
+  tlsdesc \
+  # routines
+endif
+
+ifeq ($(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
 # of some assembler macros.
 ASFLAGS-.os += $(pic-ccflag)
diff --git a/sysdeps/riscv/dl-lookupcfg.h b/sysdeps/riscv/dl-lookupcfg.h
new file mode 100644
index 0000000000..d75a48f50c
--- /dev/null
+++ b/sysdeps/riscv/dl-lookupcfg.h
@@ -0,0 +1,27 @@ 
+/* Configuration of lookup functions.
+   Copyright (C) 2023 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 c0c9bd93ad..9f10160dbb 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>
@@ -50,7 +51,8 @@ 
      || (__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.  */
@@ -219,6 +221,34 @@  elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
 	}
       break;
 
+    case R_RISCV_TLSDESC:
+      struct tlsdesc *td = (struct tlsdesc *) addr_field;
+      if (sym == NULL)
+	{
+	  td->entry = _dl_tlsdesc_undefweak;
+	  td->arg = (void *) reloc->r_addend;
+	}
+      else
+	{
+# ifndef SHARED
+	  CHECK_STATIC_TLS (map, sym_map);
+# else
+	  if (!TRY_STATIC_TLS (map, sym_map))
+	    {
+	      td->entry = _dl_tlsdesc_dynamic;
+	      td->arg = _dl_make_tlsdesc_dynamic (
+		  sym_map, sym->st_value + reloc->r_addend);
+	    }
+	  else
+# endif
+	    {
+	      td->entry = _dl_tlsdesc_return;
+	      td->arg
+		  = (void *) (TLS_TPREL_VALUE (sym_map, sym) + reloc->r_addend);
+	    }
+	}
+      break;
+
     case R_RISCV_COPY:
       {
 	if (__glibc_unlikely (sym == NULL))
@@ -289,6 +319,24 @@  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..06fe134a38
--- /dev/null
+++ b/sysdeps/riscv/dl-tlsdesc.S
@@ -0,0 +1,205 @@ 
+/* Thread-local storage handling in the ELF dynamic linker.
+   RISC-V version.
+   Copyright (C) 2023 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>
+
+#define FRAME_SIZE_FAST (-((-3 * SZREG) & ALMASK))
+
+#ifdef __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	__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)
+#endif
diff --git a/sysdeps/riscv/dl-tlsdesc.h b/sysdeps/riscv/dl-tlsdesc.h
new file mode 100644
index 0000000000..0c9b83f43d
--- /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) 2023 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/tlsdesc.c b/sysdeps/riscv/tlsdesc.c
new file mode 100644
index 0000000000..d013bc7135
--- /dev/null
+++ b/sysdeps/riscv/tlsdesc.c
@@ -0,0 +1,38 @@ 
+/* Manage TLS descriptors.  RISC-V version.
+   Copyright (C) 2023 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/unix/sysv/linux/riscv/localplt.data b/sysdeps/unix/sysv/linux/riscv/localplt.data
index ea887042e0..01710df22d 100644
--- a/sysdeps/unix/sysv/linux/riscv/localplt.data
+++ b/sysdeps/unix/sysv/linux/riscv/localplt.data
@@ -6,3 +6,5 @@  libc.so: free
 libc.so: malloc
 libc.so: memset ?
 libc.so: realloc
+# The dynamic loader needs __tls_get_addr for TLS.
+ld.so: __tls_get_addr