[PATCH v8 2/2] x86: Update _dl_tlsdesc_dynamic to preserve caller-saved registers
H.J. Lu
hjl.tools@gmail.com
Sat Feb 24 17:30:46 GMT 2024
On Sat, Feb 24, 2024 at 9:09 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> On Fri, Feb 16, 2024 at 9:17 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > Compiler generates the following instruction sequence for GNU2 dynamic
> > TLS access:
> >
> > leaq tls_var@TLSDESC(%rip), %rax
> > call *tls_var@TLSCALL(%rax)
> >
> > or
> >
> > leal tls_var@TLSDESC(%ebx), %eax
> > call *tls_var@TLSCALL(%eax)
> >
> > CALL instruction is transparent to compiler which assumes all registers,
> > except for EFLAGS and RAX/EAX, are unchanged after CALL. When
> > _dl_tlsdesc_dynamic is called, it calls __tls_get_addr on the slow
> > path. __tls_get_addr is a normal function which doesn't preserve any
> > caller-saved registers. _dl_tlsdesc_dynamic saved and restored integer
> > caller-saved registers, but didn't preserve any other caller-saved
> > registers. Add _dl_tlsdesc_dynamic IFUNC functions for FNSAVE, FXSAVE,
> > XSAVE and XSAVEC to save and restore all caller-saved registers. This
> > fixes BZ #31372.
> >
> > Add GLRO(dl_x86_64_runtime_resolve) with GLRO(dl_x86_tlsdesc_dynamic)
> > to optimize elf_machine_runtime_setup.
> > ---
> > elf/Makefile | 14 ++
> > elf/tst-gnu2-tls2.c | 120 ++++++++++++
> > elf/tst-gnu2-tls2.h | 36 ++++
> > elf/tst-gnu2-tls2mod0.c | 31 +++
> > elf/tst-gnu2-tls2mod1.c | 31 +++
> > elf/tst-gnu2-tls2mod2.c | 31 +++
> > sysdeps/i386/dl-machine.h | 2 +-
> > sysdeps/i386/dl-tlsdesc-dynamic.h | 190 +++++++++++++++++++
> > sysdeps/i386/dl-tlsdesc.S | 115 +++++------
> > sysdeps/x86/Makefile | 7 +-
> > sysdeps/x86/cpu-features.c | 56 +++++-
> > sysdeps/x86/dl-procinfo.c | 16 ++
> > sysdeps/{x86_64 => x86}/features-offsets.sym | 2 +
> > sysdeps/x86/sysdep.h | 6 +
> > sysdeps/x86/tst-gnu2-tls2.c | 20 ++
> > sysdeps/x86_64/Makefile | 2 +-
> > sysdeps/x86_64/dl-machine.h | 19 +-
> > sysdeps/x86_64/dl-procinfo.c | 16 ++
> > sysdeps/x86_64/dl-tlsdesc-dynamic.h | 166 ++++++++++++++++
> > sysdeps/x86_64/dl-tlsdesc.S | 108 ++++-------
> > sysdeps/x86_64/dl-trampoline-save.h | 34 ++++
> > sysdeps/x86_64/dl-trampoline-state.h | 51 +++++
> > sysdeps/x86_64/dl-trampoline.S | 20 +-
> > sysdeps/x86_64/dl-trampoline.h | 34 +---
> > 24 files changed, 914 insertions(+), 213 deletions(-)
> > create mode 100644 elf/tst-gnu2-tls2.c
> > create mode 100644 elf/tst-gnu2-tls2.h
> > create mode 100644 elf/tst-gnu2-tls2mod0.c
> > create mode 100644 elf/tst-gnu2-tls2mod1.c
> > create mode 100644 elf/tst-gnu2-tls2mod2.c
> > create mode 100644 sysdeps/i386/dl-tlsdesc-dynamic.h
> > rename sysdeps/{x86_64 => x86}/features-offsets.sym (89%)
> > create mode 100644 sysdeps/x86/tst-gnu2-tls2.c
> > create mode 100644 sysdeps/x86_64/dl-tlsdesc-dynamic.h
> > create mode 100644 sysdeps/x86_64/dl-trampoline-save.h
> > create mode 100644 sysdeps/x86_64/dl-trampoline-state.h
> >
> > diff --git a/elf/Makefile b/elf/Makefile
> > index 5d78b659ce..030db4d207 100644
> > --- a/elf/Makefile
> > +++ b/elf/Makefile
> > @@ -424,6 +424,7 @@ tests += \
> > tst-glibc-hwcaps-prepend \
> > tst-global1 \
> > tst-global2 \
> > + tst-gnu2-tls2 \
> > tst-initfinilazyfail \
> > tst-initorder \
> > tst-initorder2 \
> > @@ -846,6 +847,9 @@ modules-names += \
> > tst-filterobj-flt \
> > tst-finilazyfailmod \
> > tst-globalmod2 \
> > + tst-gnu2-tls2mod0 \
> > + tst-gnu2-tls2mod1 \
> > + tst-gnu2-tls2mod2 \
> > tst-initlazyfailmod \
> > tst-initorder2a \
> > tst-initorder2b \
> > @@ -3044,8 +3048,18 @@ $(objpfx)tst-tlsgap.out: \
> > $(objpfx)tst-tlsgap-mod0.so \
> > $(objpfx)tst-tlsgap-mod1.so \
> > $(objpfx)tst-tlsgap-mod2.so
> > +
> > +$(objpfx)tst-gnu2-tls2: $(shared-thread-library)
> > +$(objpfx)tst-gnu2-tls2.out: \
> > + $(objpfx)tst-gnu2-tls2mod0.so \
> > + $(objpfx)tst-gnu2-tls2mod1.so \
> > + $(objpfx)tst-gnu2-tls2mod2.so
> > +
> > ifeq (yes,$(have-mtls-dialect-gnu2))
> > CFLAGS-tst-tlsgap-mod0.c += -mtls-dialect=gnu2
> > CFLAGS-tst-tlsgap-mod1.c += -mtls-dialect=gnu2
> > CFLAGS-tst-tlsgap-mod2.c += -mtls-dialect=gnu2
> > +CFLAGS-tst-gnu2-tls2mod0.c += -mtls-dialect=gnu2
> > +CFLAGS-tst-gnu2-tls2mod1.c += -mtls-dialect=gnu2
> > +CFLAGS-tst-gnu2-tls2mod2.c += -mtls-dialect=gnu2
> > endif
> > diff --git a/elf/tst-gnu2-tls2.c b/elf/tst-gnu2-tls2.c
> > new file mode 100644
> > index 0000000000..8039ba614d
> > --- /dev/null
> > +++ b/elf/tst-gnu2-tls2.c
> > @@ -0,0 +1,120 @@
> > +/* Test TLSDESC relocation.
> > + Copyright (C) 2024 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
> > + <http://www.gnu.org/licenses/>. */
> > +
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <string.h>
> > +#include <dlfcn.h>
> > +#include <pthread.h>
> > +#include <support/xdlfcn.h>
> > +#include <support/xthread.h>
> > +#include <support/check.h>
> > +#include <support/test-driver.h>
> > +#include "tst-gnu2-tls2.h"
> > +
> > +#ifndef IS_SUPPORTED
> > +# define IS_SUPPORTED() true
> > +#endif
> > +
> > +/* An architecture can define it to clobber caller-saved registers in
> > + malloc below to verify that the implicit TLSDESC call won't change
> > + caller-saved registers. */
> > +#ifndef PREPARE_MALLOC
> > +# define PREPARE_MALLOC()
> > +#endif
> > +
> > +extern void * __libc_malloc (size_t);
> > +
> > +size_t malloc_counter = 0;
> > +
> > +void *
> > +malloc (size_t n)
> > +{
> > + PREPARE_MALLOC ();
> > + malloc_counter++;
> > + return __libc_malloc (n);
> > +}
> > +
> > +static void *mod[3];
> > +#define MOD(i) "tst-gnu2-tls2mod" #i ".so"
> > +static const char *modname[3] = { MOD(0), MOD(1), MOD(2) };
> > +#undef MOD
> > +
> > +static void
> > +open_mod (int i)
> > +{
> > + mod[i] = xdlopen (modname[i], RTLD_LAZY);
> > + printf ("open %s\n", modname[i]);
> > +}
> > +
> > +static void
> > +close_mod (int i)
> > +{
> > + xdlclose (mod[i]);
> > + mod[i] = NULL;
> > + printf ("close %s\n", modname[i]);
> > +}
> > +
> > +static void
> > +access_mod (int i, const char *sym)
> > +{
> > + struct tls var = { -1, -1, -1, -1 };
> > + struct tls *(*f) (struct tls *) = xdlsym (mod[i], sym);
> > + /* Check that our malloc is called. */
> > + malloc_counter = 0;
> > + struct tls *p = f (&var);
> > + TEST_VERIFY (malloc_counter != 0);
> > + printf ("access %s: %s() = %p\n", modname[i], sym, p);
> > + TEST_VERIFY_EXIT (memcmp (p, &var, sizeof (var)) == 0);
> > + ++(p->a);
> > +}
> > +
> > +static void *
> > +start (void *arg)
> > +{
> > + /* The DTV generation is at the last dlopen of mod0 and the
> > + entry for mod1 is NULL. */
> > +
> > + open_mod (1); /* Reuse modid of mod1. Uses dynamic TLS. */
> > +
> > + /* Force the slow path in GNU2 TLS descriptor call. */
> > + access_mod (1, "apply_tls");
> > +
> > + return arg;
> > +}
> > +
> > +static int
> > +do_test (void)
> > +{
> > + if (!IS_SUPPORTED ())
> > + return EXIT_UNSUPPORTED;
> > +
> > + open_mod (0);
> > + open_mod (1);
> > + open_mod (2);
> > + close_mod (0);
> > + close_mod (1); /* Create modid gap at mod1. */
> > + open_mod (0); /* Reuse modid of mod0, bump generation count. */
> > +
> > + /* Create a thread where DTV of mod1 is NULL. */
> > + pthread_t t = xpthread_create (NULL, start, NULL);
> > + xpthread_join (t);
> > + return 0;
> > +}
> > +
> > +#include <support/test-driver.c>
>
> The change looks good but this is still failing on arm.
>
> ```
> FAIL: elf/tst-gnu2-tls2
> original exit status 1
> open tst-gnu2-tls2mod0.so
> open tst-gnu2-tls2mod1.so
> open tst-gnu2-tls2mod2.so
> close tst-gnu2-tls2mod0.so
> close tst-gnu2-tls2mod1.so
> open tst-gnu2-tls2mod0.so
> open tst-gnu2-tls2mod1.so
> Didn't expect signal from child: got `Segmentation fault'
> ```
>
> HJ can you add some more logging to its clear exactly where
> the fault is? (looks to be malloc or xdlsym).
The new test may fail on targets which don't preserve all
caller-saved registers in _dl_tlsdesc_dynamic.
> Are there any other arch this is failing on? I.e is this an arm
> bug or buggy test?
>
It is a bug on arm:
https://github.com/zatrazz/glibc/commits/azanella/tls-descriptor-fixes-arm/
...
--
H.J.
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