git: 2d049e4de292 - stable/15 - i386 rtld: implement support for TLSDESC relocation
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Date: Sat, 12 Sep 2026 00:28:07 UTC
The branch stable/15 has been updated by kib:
URL: https://cgit.FreeBSD.org/src/commit/?id=2d049e4de2925a495c54e502c77598f2f833eb5f
commit 2d049e4de2925a495c54e502c77598f2f833eb5f
Author: Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2026-08-25 12:26:50 +0000
Commit: Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2026-09-11 06:59:53 +0000
i386 rtld: implement support for TLSDESC relocation
(cherry picked from commit d45d7aea6197a91b794808d508295a74ce5be0cd)
---
libexec/rtld-elf/amd64/rtld_start.S | 25 ++++++++++
libexec/rtld-elf/i386/reloc.c | 95 +++++++++++++++++++++++++++++++++++-
libexec/rtld-elf/i386/rtld_machdep.h | 31 ++++++++++--
libexec/rtld-elf/i386/rtld_start.S | 36 ++++++++++++++
4 files changed, 183 insertions(+), 4 deletions(-)
diff --git a/libexec/rtld-elf/amd64/rtld_start.S b/libexec/rtld-elf/amd64/rtld_start.S
index 7f85a9f94d5c..dcc168a33c57 100644
--- a/libexec/rtld-elf/amd64/rtld_start.S
+++ b/libexec/rtld-elf/amd64/rtld_start.S
@@ -171,4 +171,29 @@ rtld_dynamic_addr:
.cfi_endproc
.size rtld_dynamic_addr, . - rtld_dynamic_addr
+rtld_tlsdesc_static:
+ .globl rtld_tlsdesc_static
+ .type rtld_tlsdesc_static,@function
+ .cfi_startproc
+ movq 8(%rax), %rax
+ ret
+ .cfi_endproc
+ .size rtld_tlsdesc_static, . - rtld_tlsdesc_static
+
+rtld_tlsdesc_undef:
+ .globl rtld_tlsdesc_undef
+ .type rtld_tlsdesc_undef,@function
+ .cfi_startproc
+ ret
+ .cfi_endproc
+ .size rtld_tlsdesc_undef, . - rtld_tlsdesc_undef
+
+rtld_tlsdesc_dynamic:
+ .globl rtld_tlsdesc_static
+ .type rtld_tlsdesc_dynamic,@function
+ .cfi_startproc
+ ret
+ .cfi_endproc
+ .size rtld_tlsdesc_dynamic, . - rtld_tlsdesc_dynamic
+
.section .note.GNU-stack,"",%progbits
diff --git a/libexec/rtld-elf/i386/reloc.c b/libexec/rtld-elf/i386/reloc.c
index 060b3cb147e3..5dd495f2056c 100644
--- a/libexec/rtld-elf/i386/reloc.c
+++ b/libexec/rtld-elf/i386/reloc.c
@@ -51,6 +51,22 @@
#include "rtld.h"
#include "rtld_tls.h"
+void
+md_obj_entry_init(Obj_Entry *obj)
+{
+ STAILQ_INIT(&obj->tlsdesc_dynargs);
+}
+
+void
+md_obj_entry_fini(Obj_Entry *obj)
+{
+ struct tlsdesc_dynarg *tda, *t;
+
+ STAILQ_FOREACH_SAFE(tda, &obj->tlsdesc_dynargs, link, t) {
+ free(tda);
+ }
+}
+
/*
* Process the special R_386_COPY relocations in the main program. These
* copy data from a shared object into a region in the main program's BSS
@@ -125,6 +141,60 @@ init_pltgot(Obj_Entry *obj)
}
}
+static struct tlsdesc_dynarg *
+reloc_tlsdesc_alloc(Obj_Entry *obj, Elf_Addr tlsoffs)
+{
+ struct tlsdesc_dynarg *tda;
+
+ tda = xmalloc(sizeof(struct tlsdesc_dynarg));
+ tda->tlsinfo.ti_module = obj->tlsindex;
+ tda->tlsinfo.ti_offset = tlsoffs;
+ STAILQ_INSERT_TAIL(&obj->tlsdesc_dynargs, tda, link);
+ return (tda);
+}
+
+static void
+reloc_tlsdesc(const Obj_Entry *obj, const Elf_Rel *rel,
+ struct tlsdesc *where, int flags, RtldLockState *lockstate)
+{
+ const Elf_Sym *def;
+ const Obj_Entry *defobj;
+ Elf_Addr offs;
+
+ dbg("reloc_tlsdesc obj %s rel %p where %p", obj->path, rel, where);
+ offs = 0;
+ if (ELF_R_SYM(rel->r_info) != 0) {
+ def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, flags,
+ NULL, lockstate);
+ if (def == NULL)
+ rtld_die();
+ if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
+ _rtld_error("%s: IFUNC for TLSDESC reloc",
+ obj->path);
+ rtld_die();
+ }
+ offs = def->st_value;
+ obj = defobj;
+ if (def->st_shndx == SHN_UNDEF) {
+ /* Weak undefined thread variable */
+ where->entry = rtld_tlsdesc_undef;
+ return;
+ }
+ }
+ offs += where->offset;
+
+ if (obj->tlsoffset != 0) {
+ /* Variable is in initialy allocated TLS segment */
+ where->entry = rtld_tlsdesc_static;
+ where->offset = offs - obj->tlsoffset;
+ } else {
+ /* TLS offest is unknown at load time, use dynamic resolving */
+ where->entry = rtld_tlsdesc_dynamic;
+ where->arg = reloc_tlsdesc_alloc(__DECONST(Obj_Entry *, obj),
+ offs);
+ }
+}
+
/* Process the non-PLT relocations. */
int
reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags,
@@ -271,6 +341,10 @@ reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags,
case R_386_IRELATIVE:
obj->irelative_nonplt = true;
break;
+ case R_386_TLS_DESC:
+ reloc_tlsdesc(obj, rel, (struct tlsdesc *)where,
+ flags, lockstate);
+ break;
default:
_rtld_error(
"%s: Unsupported relocation type %d in non-PLT relocations",
@@ -295,10 +369,10 @@ reloc_plt(Obj_Entry *obj, int flags __unused, RtldLockState *lockstate __unused)
for (rel = obj->pltrel; rel < rellim; rel++) {
Elf_Addr *where;
+ where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
switch (ELF_R_TYPE(rel->r_info)) {
case R_386_JMP_SLOT:
/* Relocate the GOT slot pointing into the PLT. */
- where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
*where += (Elf_Addr)obj->relocbase;
break;
@@ -306,6 +380,11 @@ reloc_plt(Obj_Entry *obj, int flags __unused, RtldLockState *lockstate __unused)
obj->irelative = true;
break;
+ case R_386_TLS_DESC:
+ reloc_tlsdesc(obj, rel, (struct tlsdesc *)where,
+ SYMLOOK_IN_PLT | flags, lockstate);
+ break;
+
default:
_rtld_error("Unknown relocation type %x in PLT",
ELF_R_TYPE(rel->r_info));
@@ -552,3 +631,17 @@ calculate_first_tls_offset(size_t size, size_t align, size_t offset)
{
return (calculate_tls_offset(0, 0, size, align, offset));
}
+
+__GNU_ABI ptrdiff_t
+rtld_tlsdesc_dynamic_impl(struct tlsdesc *tdp)
+{
+ struct tlsdesc_dynarg *tda;
+ struct tcb *tcb;
+ tls_index *ti;
+
+ tda = tdp->arg;
+ ti = &tda->tlsinfo;
+ tcb = _tcb_get();
+ return ((ptrdiff_t)tls_get_addr_common(tcb, ti->ti_module,
+ ti->ti_offset) - (ptrdiff_t)tcb);
+}
diff --git a/libexec/rtld-elf/i386/rtld_machdep.h b/libexec/rtld-elf/i386/rtld_machdep.h
index 574eafe432db..50c2a1bef94e 100644
--- a/libexec/rtld-elf/i386/rtld_machdep.h
+++ b/libexec/rtld-elf/i386/rtld_machdep.h
@@ -35,10 +35,14 @@
struct Struct_Obj_Entry;
-#define MD_OBJ_ENTRY
+#define MD_OBJ_ENTRY \
+ STAILQ_HEAD(, tlsdesc_dynarg) tlsdesc_dynargs;
-#define MD_OBJ_ENTRY_INIT(obj)
-#define MD_OBJ_ENTRY_FINI(obj)
+#define MD_OBJ_ENTRY_INIT(obj) md_obj_entry_init(obj)
+#define MD_OBJ_ENTRY_FINI(obj) md_obj_entry_fini(obj)
+
+void md_obj_entry_init(struct Struct_Obj_Entry *obj);
+void md_obj_entry_fini(struct Struct_Obj_Entry *obj);
/* Return the address of the .dynamic section in the dynamic linker. */
#define rtld_dynamic(obj) \
@@ -83,10 +87,31 @@ typedef struct {
void *___tls_get_addr(tls_index *ti) __GNU_ABI __exported;
void *__tls_get_addr(tls_index *ti) __exported;
+struct tlsdesc_dynarg
+{
+ tls_index tlsinfo;
+ STAILQ_ENTRY(tlsdesc_dynarg) link;
+};
+
+struct tlsdesc
+{
+ ptrdiff_t (*entry)(struct tlsdesc *) __GNU_ABI;
+ union {
+ Elf_Size offset;
+ struct tlsdesc_dynarg *arg;
+ };
+};
+
#define md_abi_variant_hook(x)
size_t calculate_first_tls_offset(size_t size, size_t align, size_t offset);
size_t calculate_tls_offset(size_t prev_offset, size_t prev_size, size_t size,
size_t align, size_t offset);
+ptrdiff_t rtld_tlsdesc_dynamic_impl(struct tlsdesc *tdp) __GNU_ABI;
+
+ptrdiff_t rtld_tlsdesc_static(struct tlsdesc *) __GNU_ABI;
+ptrdiff_t rtld_tlsdesc_undef(struct tlsdesc *) __GNU_ABI;
+ptrdiff_t rtld_tlsdesc_dynamic(struct tlsdesc *) __GNU_ABI;
+
#endif
diff --git a/libexec/rtld-elf/i386/rtld_start.S b/libexec/rtld-elf/i386/rtld_start.S
index 9dbe32d27628..d81f2d17fff4 100644
--- a/libexec/rtld-elf/i386/rtld_start.S
+++ b/libexec/rtld-elf/i386/rtld_start.S
@@ -95,4 +95,40 @@ _rtld_bind_start:
leal 4(%esp),%esp # Discard reloff, do not change eflags
ret # "Return" to target address
+rtld_tlsdesc_static:
+ .globl rtld_tlsdesc_static
+ .type rtld_tlsdesc_static,@function
+ .cfi_startproc
+ movl 4(%eax), %eax
+ ret
+ .cfi_endproc
+ .size rtld_tlsdesc_static, . - rtld_tlsdesc_static
+
+rtld_tlsdesc_undef:
+ .globl rtld_tlsdesc_undef
+ .type rtld_tlsdesc_undef,@function
+ .cfi_startproc
+ movl 4(%eax), %eax
+ subl %gs:0, %eax
+ ret
+ .cfi_endproc
+ .size rtld_tlsdesc_undef, . - rtld_tlsdesc_undef
+
+rtld_tlsdesc_dynamic:
+ .globl rtld_tlsdesc_dynamic
+ .type rtld_tlsdesc_dynamic,@function
+ .cfi_startproc
+ pushl %ebp
+ /* XXXKIB cfi */
+ movl %esp, %ebp
+ pushl %edx
+ pushl %ecx
+ call rtld_tlsdesc_dynamic_impl
+ popl %ecx
+ popl %edx
+ popl %ebp
+ ret
+ .cfi_endproc
+ .size rtld_tlsdesc_dynamic, . - rtld_tlsdesc_dynamic
+
.section .note.GNU-stack,"",%progbits