git: 858d63cf8a4f - stable/15 - amd64 rtld: implement support for TLSDESC relocation
- Go to: [ bottom of page ] [ top of archives ] [ this month ]
Date: Sat, 12 Sep 2026 00:28:08 UTC
The branch stable/15 has been updated by kib:
URL: https://cgit.FreeBSD.org/src/commit/?id=858d63cf8a4f1a41929a7440da866ea73ac12886
commit 858d63cf8a4f1a41929a7440da866ea73ac12886
Author: Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2026-08-26 09:41:59 +0000
Commit: Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2026-09-11 06:59:53 +0000
amd64 rtld: implement support for TLSDESC relocation
(cherry picked from commit 76f5fccc5fbdf2a7b42f1e4aa71fe625be32fa13)
---
libexec/rtld-elf/amd64/reloc.c | 94 ++++++++++++++++++++++++++++++++++-
libexec/rtld-elf/amd64/rtld_machdep.h | 36 ++++++++++++--
libexec/rtld-elf/amd64/rtld_start.S | 42 +++++++++++++++-
3 files changed, 166 insertions(+), 6 deletions(-)
diff --git a/libexec/rtld-elf/amd64/reloc.c b/libexec/rtld-elf/amd64/reloc.c
index b1a2069edb2f..7d6487267352 100644
--- a/libexec/rtld-elf/amd64/reloc.c
+++ b/libexec/rtld-elf/amd64/reloc.c
@@ -53,6 +53,22 @@
#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_X86_64_COPY relocations in the main program. These
* copy data from a shared object into a region in the main program's BSS
@@ -127,6 +143,61 @@ 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_Rela *rela,
+ struct tlsdesc *where, int flags, RtldLockState *lockstate)
+{
+ const Elf_Sym *def;
+ const Obj_Entry *defobj;
+ Elf_Addr offs;
+
+ dbg("reloc_tlsdesc obj %s rela %p where %p", obj->path, rela, where);
+ offs = 0;
+ if (ELF_R_SYM(rela->r_info) != 0) {
+ def = find_symdef(ELF_R_SYM(rela->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;
+ where->addend = rela->r_addend;
+ return;
+ }
+ }
+ offs += rela->r_addend;
+
+ 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,
@@ -313,6 +384,10 @@ reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld, int flags,
case R_X86_64_IRELATIVE:
obj->irelative_nonplt = true;
break;
+ case R_X86_64_TLSDESC:
+ reloc_tlsdesc(obj, rela, (struct tlsdesc *)where,
+ flags, lockstate);
+ break;
/*
* missing:
@@ -334,7 +409,7 @@ done:
/* Process the PLT relocations. */
int
-reloc_plt(Obj_Entry *obj, int flags __unused, RtldLockState *lockstate __unused)
+reloc_plt(Obj_Entry *obj, int flags, RtldLockState *lockstate)
{
const Elf_Rela *relalim;
const Elf_Rela *rela;
@@ -344,10 +419,10 @@ reloc_plt(Obj_Entry *obj, int flags __unused, RtldLockState *lockstate __unused)
for (rela = obj->pltrela; rela < relalim; rela++) {
Elf_Addr *where;
+ where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
switch (ELF_R_TYPE(rela->r_info)) {
case R_X86_64_JMP_SLOT:
/* Relocate the GOT slot pointing into the PLT. */
- where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
*where += (Elf_Addr)obj->relocbase;
break;
@@ -355,6 +430,11 @@ reloc_plt(Obj_Entry *obj, int flags __unused, RtldLockState *lockstate __unused)
obj->irelative = true;
break;
+ case R_X86_64_TLSDESC:
+ reloc_tlsdesc(obj, rela, (struct tlsdesc *)where,
+ SYMLOOK_IN_PLT | flags, lockstate);
+ break;
+
default:
_rtld_error("Unknown relocation type %x in PLT",
(unsigned int)ELF_R_TYPE(rela->r_info));
@@ -580,3 +660,13 @@ calculate_first_tls_offset(size_t size, size_t align, size_t offset)
{
return (calculate_tls_offset(0, 0, size, align, offset));
}
+
+ptrdiff_t
+rtld_tlsdesc_dynamic_impl(struct tlsdesc_dynarg *tda, struct tcb *tcb)
+{
+ tls_index *ti;
+
+ ti = &tda->tlsinfo;
+ return ((ptrdiff_t)tls_get_addr_common(tcb, ti->ti_module,
+ ti->ti_offset) - (ptrdiff_t)tcb);
+}
diff --git a/libexec/rtld-elf/amd64/rtld_machdep.h b/libexec/rtld-elf/amd64/rtld_machdep.h
index 53a3cd29f967..7eadba62b9f6 100644
--- a/libexec/rtld-elf/amd64/rtld_machdep.h
+++ b/libexec/rtld-elf/amd64/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. */
Elf_Dyn *rtld_dynamic_addr(void);
@@ -80,9 +84,35 @@ typedef struct {
void *__tls_get_addr(tls_index *ti) __exported;
+#define __NONE_ABI /* Cannot be expressed in C */
+
+struct tlsdesc_dynarg
+{
+ tls_index tlsinfo;
+ STAILQ_ENTRY(tlsdesc_dynarg) link;
+};
+
+struct tlsdesc
+{
+ ptrdiff_t (*entry)(struct tlsdesc *) __NONE_ABI;
+ union {
+ Elf_Ssize addend;
+ 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_dynarg *tda,
+ struct tcb *tcb);
+
+ptrdiff_t rtld_tlsdesc_static(struct tlsdesc *) __NONE_ABI;
+ptrdiff_t rtld_tlsdesc_undef(struct tlsdesc *) __NONE_ABI;
+ptrdiff_t rtld_tlsdesc_dynamic(struct tlsdesc *) __NONE_ABI;
+
#endif
diff --git a/libexec/rtld-elf/amd64/rtld_start.S b/libexec/rtld-elf/amd64/rtld_start.S
index dcc168a33c57..b1a619028fd0 100644
--- a/libexec/rtld-elf/amd64/rtld_start.S
+++ b/libexec/rtld-elf/amd64/rtld_start.S
@@ -184,15 +184,55 @@ rtld_tlsdesc_undef:
.globl rtld_tlsdesc_undef
.type rtld_tlsdesc_undef,@function
.cfi_startproc
+ movq 8(%rax), %rax
+ subq %fs:0, %rax
ret
.cfi_endproc
.size rtld_tlsdesc_undef, . - rtld_tlsdesc_undef
rtld_tlsdesc_dynamic:
- .globl rtld_tlsdesc_static
+ .globl rtld_tlsdesc_dynamic
.type rtld_tlsdesc_dynamic,@function
.cfi_startproc
+ pushq %rbp
+ /* XXXKIB cfi */
+ movq %rsp,%rbp
+ pushq %rdx
+ pushq %rcx
+ pushq %rsi
+ pushq %rdi
+ movq 8(%rax), %rdi /* arg->arg */
+ movq %fs:0, %rsi /* tcb */
+
+ movq 8(%rsi), %rcx /* dtv */
+ movq (%rcx), %rdx /* dtv_gen */
+ cmpq %rdx, tls_dtv_generation(%rip)
+ jne 2f
+ movq (%rdi), %rax /* arg->tlsinfo.ti_module */
+ dec %rax
+ movq 16(%rcx, %rax, 8), %rax /* dtv_tls */
+ testq %rax, %rax
+ je 2f
+ addq 8(%rdi), %rax /* arg->offset */
+ subq %rsi, %rax
+1:
+ popq %rdi
+ popq %rsi
+ popq %rcx
+ popq %rdx
+ popq %rbp
ret
+2:
+ pushq %r8
+ pushq %r9
+ pushq %r10
+ pushq %r11
+ call rtld_tlsdesc_dynamic_impl
+ popq %r11
+ popq %r10
+ popq %r9
+ popq %r8
+ jmp 1b
.cfi_endproc
.size rtld_tlsdesc_dynamic, . - rtld_tlsdesc_dynamic