When libgcc is built with pac-ret, it requires to autenticate the
unwinding frame based on CFI information. The _dl_tlsdesc_dynamic
uses a custom calling convention, where it is responsible to save
and restore all registers it might use (even volatile).
The pac-ret support added by
1be3d6eb823d8b952fa54b7bbc90cbecb8981380
was added only on the slow-path, but the fast path also adds DWARF
Register Rule Instruction (cfi_adjust_cfa_offset) since it requires
to save/restore some auxiliary register. It seems that this is not
fully supported neither by libgcc nor AArch64 ABI [1].
Instead, move paciasp/autiasp to function prologue/epilogue to be
used on both fast and slow paths.
I also corrected the _dl_tlsdesc_dynamic comment description, it was
copied from i386 implementation without any adjustment.
Checked on aarch64-linux-gnu with a toolchain built with
--enable-standard-branch-protection on a system with pac-ret
support.
[1] https://github.com/ARM-software/abi-aa/blob/main/aadwarf64/aadwarf64.rst#id1
Reviewed-by: Yury Khrustalev <yury.khrustalev@arm.com>
object referenced by the argument.
ptrdiff_t
- __attribute__ ((__regparm__ (1)))
_dl_tlsdesc_dynamic (struct tlsdesc *tdp)
{
struct tlsdesc_dynamic_arg *td = tdp->arg;
- dtv_t *dtv = *(dtv_t **)((char *)__thread_pointer + TCBHEAD_DTV);
+ 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;
+ - __thread_pointer();
- return ___tls_get_addr (&td->tlsinfo) - __thread_pointer;
+ return __tls_get_addr (&td->tlsinfo) - __thread_pointer();
}
*/
cfi_startproc
.align 2
_dl_tlsdesc_dynamic:
+# if HAVE_AARCH64_PAC_RET
+ PACIASP
+ cfi_window_save
+# else
BTI_C
+# endif
/* Save just enough registers to support fast path, if we fall
into slow path we will save additional registers. */
1:
ldp x3, x4, [sp, #16]
ldp x1, x2, [sp], #32
+# if HAVE_AARCH64_PAC_RET
+ AUTIASP
+ cfi_window_save
+# endif
cfi_adjust_cfa_offset (-32)
RET
2:
/* Save the remaining registers that we must treat as caller save. */
cfi_restore_state
-# if HAVE_AARCH64_PAC_RET
- PACIASP
- cfi_window_save
-# endif
# define NSAVEXREGPAIRS 8
stp x29, x30, [sp,#-16*NSAVEXREGPAIRS]!
cfi_adjust_cfa_offset (16*NSAVEXREGPAIRS)
cfi_adjust_cfa_offset (-16*NSAVEXREGPAIRS)
cfi_restore (x29)
cfi_restore (x30)
-# if HAVE_AARCH64_PAC_RET
- AUTIASP
- cfi_window_save
-# endif
b 1b
cfi_endproc
.size _dl_tlsdesc_dynamic, .-_dl_tlsdesc_dynamic
+ifeq ($(subdir),elf)
+tests += \
+ tst-tlsdesc-pac \
+ # tests
+modules-names += \
+ tst-tlsdesc-pac-mod \
+ # modules-names
+
+LDFLAGS-tst-tlsdesc-pac = -rdynamic
+
+$(objpfx)tst-tlsdesc-pac.out: $(objpfx)tst-tlsdesc-pac-mod.so
+endif
+
ifeq ($(subdir),misc)
sysdep_headers += sys/elf.h
tests += \
--- /dev/null
+/* AArch64 tests for unwinding TLSDESC (BZ 32612)
+ Copyright (C) 2025 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/>. */
+
+_Thread_local int foo;
+/* Make the TLS segment large enough to trigger _dl_tlsdesc_dynamic. */
+_Thread_local int foobar[1000];
+
+void
+bar (void)
+{
+ foo = 1;
+}
--- /dev/null
+/* AArch64 tests for unwinding TLSDESC (BZ 32612)
+ Copyright (C) 2025 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 <stdlib.h>
+#include <unwind.h>
+#include <support/xdlfcn.h>
+
+static _Unwind_Reason_Code
+unwind_callback (struct _Unwind_Context* context, void* closure)
+{
+ return _URC_NO_REASON;
+}
+
+/* Assume that TLS variable from tst-tlsdesc-pac-mod.so will trigger
+ the slow-path that allocates the required memory with malloc. */
+void *
+malloc (size_t s)
+{
+ _Unwind_Backtrace (unwind_callback, NULL);
+ return calloc (1, s);
+}
+
+static int
+do_test (void)
+{
+ void *h = xdlopen ("tst-tlsdesc-pac-mod.so", RTLD_LAZY);
+ void (*func)(void) = xdlsym (h, "bar");
+ func ();
+
+ return 0;
+}
+
+#include <support/test-driver.c>
projects / thirdparty / glibc.git / commitdiff
