diff options
Diffstat (limited to 'sysdeps/aarch64')
| -rw-r--r-- | sysdeps/aarch64/dl-tlsdesc.S | 37 | ||||
| -rw-r--r-- | sysdeps/aarch64/dl-tlsdesc.h | 3 | ||||
| -rw-r--r-- | sysdeps/aarch64/tlsdesc.c | 36 |
3 files changed, 64 insertions, 12 deletions
diff --git a/sysdeps/aarch64/dl-tlsdesc.S b/sysdeps/aarch64/dl-tlsdesc.S index be9b9b3..c7adf79 100644 --- a/sysdeps/aarch64/dl-tlsdesc.S +++ b/sysdeps/aarch64/dl-tlsdesc.S @@ -79,6 +79,29 @@ _dl_tlsdesc_return: cfi_endproc .size _dl_tlsdesc_return, .-_dl_tlsdesc_return + /* Same as _dl_tlsdesc_return but with synchronization for + lazy relocation. + Prototype: + _dl_tlsdesc_return_lazy (tlsdesc *) ; + */ + .hidden _dl_tlsdesc_return_lazy + .global _dl_tlsdesc_return_lazy + .type _dl_tlsdesc_return_lazy,%function + cfi_startproc + .align 2 +_dl_tlsdesc_return_lazy: + /* The ldar here happens after the load from [x0] at the call site + (that is generated by the compiler as part of the TLS access ABI), + so it reads the same value (this function is the final value of + td->entry) and thus it synchronizes with the release store to + td->entry in _dl_tlsdesc_resolve_rela_fixup ensuring that the load + from [x0,#8] here happens after the initialization of td->arg. */ + ldar xzr, [x0] + ldr x0, [x0, #8] + RET + cfi_endproc + .size _dl_tlsdesc_return_lazy, .-_dl_tlsdesc_return_lazy + /* Handler for undefined weak TLS symbols. Prototype: _dl_tlsdesc_undefweak (tlsdesc *); @@ -96,6 +119,13 @@ _dl_tlsdesc_return: _dl_tlsdesc_undefweak: str x1, [sp, #-16]! cfi_adjust_cfa_offset(16) + /* The ldar here happens after the load from [x0] at the call site + (that is generated by the compiler as part of the TLS access ABI), + so it reads the same value (this function is the final value of + td->entry) and thus it synchronizes with the release store to + td->entry in _dl_tlsdesc_resolve_rela_fixup ensuring that the load + from [x0,#8] here happens after the initialization of td->arg. */ + ldar xzr, [x0] ldr x0, [x0, #8] mrs x1, tpidr_el0 sub x0, x0, x1 @@ -152,6 +182,13 @@ _dl_tlsdesc_dynamic: stp x3, x4, [sp, #32+16*1] mrs x4, tpidr_el0 + /* The ldar here happens after the load from [x0] at the call site + (that is generated by the compiler as part of the TLS access ABI), + so it reads the same value (this function is the final value of + td->entry) and thus it synchronizes with the release store to + td->entry in _dl_tlsdesc_resolve_rela_fixup ensuring that the load + from [x0,#8] here happens after the initialization of td->arg. */ + ldar xzr, [x0] ldr x1, [x0,#8] ldr x0, [x4] ldr x3, [x1,#16] diff --git a/sysdeps/aarch64/dl-tlsdesc.h b/sysdeps/aarch64/dl-tlsdesc.h index 7a1285e..e6c0078 100644 --- a/sysdeps/aarch64/dl-tlsdesc.h +++ b/sysdeps/aarch64/dl-tlsdesc.h @@ -46,6 +46,9 @@ extern ptrdiff_t attribute_hidden _dl_tlsdesc_return (struct tlsdesc *); extern ptrdiff_t attribute_hidden +_dl_tlsdesc_return_lazy (struct tlsdesc *); + +extern ptrdiff_t attribute_hidden _dl_tlsdesc_undefweak (struct tlsdesc *); extern ptrdiff_t attribute_hidden diff --git a/sysdeps/aarch64/tlsdesc.c b/sysdeps/aarch64/tlsdesc.c index 4821f8c..9f3ff9b 100644 --- a/sysdeps/aarch64/tlsdesc.c +++ b/sysdeps/aarch64/tlsdesc.c @@ -25,6 +25,7 @@ #include <dl-tlsdesc.h> #include <dl-unmap-segments.h> #include <tlsdeschtab.h> +#include <atomic.h> /* The following functions take an entry_check_offset argument. It's computed by the caller as an offset between its entry point and the @@ -39,11 +40,15 @@ void attribute_hidden -_dl_tlsdesc_resolve_rela_fixup (struct tlsdesc volatile *td, - struct link_map *l) +_dl_tlsdesc_resolve_rela_fixup (struct tlsdesc *td, struct link_map *l) { - const ElfW(Rela) *reloc = td->arg; + const ElfW(Rela) *reloc = atomic_load_relaxed (&td->arg); + /* After GL(dl_load_lock) is grabbed only one caller can see td->entry in + initial state in _dl_tlsdesc_resolve_early_return_p, other concurrent + callers will return and retry calling td->entry. The updated td->entry + synchronizes with the single writer so all read accesses here can use + relaxed order. */ if (_dl_tlsdesc_resolve_early_return_p (td, (void*)(D_PTR (l, l_info[ADDRIDX (DT_TLSDESC_PLT)]) + l->l_addr))) return; @@ -86,8 +91,10 @@ _dl_tlsdesc_resolve_rela_fixup (struct tlsdesc volatile *td, if (!sym) { - td->arg = (void*) reloc->r_addend; - td->entry = _dl_tlsdesc_undefweak; + atomic_store_relaxed (&td->arg, (void *) reloc->r_addend); + /* This release store synchronizes with the ldar acquire load + instruction in _dl_tlsdesc_undefweak. */ + atomic_store_release (&td->entry, _dl_tlsdesc_undefweak); } else { @@ -96,16 +103,22 @@ _dl_tlsdesc_resolve_rela_fixup (struct tlsdesc volatile *td, # else if (!TRY_STATIC_TLS (l, result)) { - td->arg = _dl_make_tlsdesc_dynamic (result, sym->st_value + void *p = _dl_make_tlsdesc_dynamic (result, sym->st_value + reloc->r_addend); - td->entry = _dl_tlsdesc_dynamic; + atomic_store_relaxed (&td->arg, p); + /* This release store synchronizes with the ldar acquire load + instruction in _dl_tlsdesc_dynamic. */ + atomic_store_release (&td->entry, _dl_tlsdesc_dynamic); } else # endif { - td->arg = (void*) (sym->st_value + result->l_tls_offset + void *p = (void*) (sym->st_value + result->l_tls_offset + reloc->r_addend); - td->entry = _dl_tlsdesc_return; + atomic_store_relaxed (&td->arg, p); + /* This release store synchronizes with the ldar acquire load + instruction in _dl_tlsdesc_return_lazy. */ + atomic_store_release (&td->entry, _dl_tlsdesc_return_lazy); } } @@ -120,11 +133,10 @@ _dl_tlsdesc_resolve_rela_fixup (struct tlsdesc volatile *td, void attribute_hidden -_dl_tlsdesc_resolve_hold_fixup (struct tlsdesc volatile *td, - void *caller) +_dl_tlsdesc_resolve_hold_fixup (struct tlsdesc *td, void *caller) { /* Maybe we're lucky and can return early. */ - if (caller != td->entry) + if (caller != atomic_load_relaxed (&td->entry)) return; /* Locking here will stop execution until the running resolver runs |