From 4352e2cc934b2874dba37397157bf890fcee455a Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Fri, 28 Mar 2025 14:27:45 -0300 Subject: [PATCH] aarch64: Fix _dl_tlsdesc_dynamic unwind for pac-ret (BZ 32612) 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 --- sysdeps/aarch64/dl-tlsdesc.S | 24 +++++----- sysdeps/unix/sysv/linux/aarch64/Makefile | 13 +++++ .../sysv/linux/aarch64/tst-tlsdesc-pac-mod.c | 27 +++++++++++ .../unix/sysv/linux/aarch64/tst-tlsdesc-pac.c | 48 +++++++++++++++++++ 4 files changed, 100 insertions(+), 12 deletions(-) create mode 100644 sysdeps/unix/sysv/linux/aarch64/tst-tlsdesc-pac-mod.c create mode 100644 sysdeps/unix/sysv/linux/aarch64/tst-tlsdesc-pac.c diff --git a/sysdeps/aarch64/dl-tlsdesc.S b/sysdeps/aarch64/dl-tlsdesc.S index 68afc443f7..fc40d66c07 100644 --- a/sysdeps/aarch64/dl-tlsdesc.S +++ b/sysdeps/aarch64/dl-tlsdesc.S @@ -119,20 +119,19 @@ _dl_tlsdesc_undefweak: 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(); } */ @@ -142,7 +141,12 @@ _dl_tlsdesc_undefweak: 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. */ @@ -173,6 +177,10 @@ _dl_tlsdesc_dynamic: 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: @@ -182,10 +190,6 @@ _dl_tlsdesc_dynamic: /* 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) @@ -236,10 +240,6 @@ _dl_tlsdesc_dynamic: 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 diff --git a/sysdeps/unix/sysv/linux/aarch64/Makefile b/sysdeps/unix/sysv/linux/aarch64/Makefile index 0839f0b08c..15a2b4471d 100644 --- a/sysdeps/unix/sysv/linux/aarch64/Makefile +++ b/sysdeps/unix/sysv/linux/aarch64/Makefile @@ -1,3 +1,16 @@ +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 += \ diff --git a/sysdeps/unix/sysv/linux/aarch64/tst-tlsdesc-pac-mod.c b/sysdeps/unix/sysv/linux/aarch64/tst-tlsdesc-pac-mod.c new file mode 100644 index 0000000000..d34c8beda9 --- /dev/null +++ b/sysdeps/unix/sysv/linux/aarch64/tst-tlsdesc-pac-mod.c @@ -0,0 +1,27 @@ +/* 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 + . */ + +_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; +} diff --git a/sysdeps/unix/sysv/linux/aarch64/tst-tlsdesc-pac.c b/sysdeps/unix/sysv/linux/aarch64/tst-tlsdesc-pac.c new file mode 100644 index 0000000000..24d656aafc --- /dev/null +++ b/sysdeps/unix/sysv/linux/aarch64/tst-tlsdesc-pac.c @@ -0,0 +1,48 @@ +/* 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 + . */ + +#include +#include +#include + +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