[PATCH 1/4] nptl: fix potential merge of __rseq_* relro symbols
DJ Delorie
dj@redhat.com
Fri Mar 1 04:08:21 GMT 2024
LGTM
Reviewed-by: DJ Delorie <dj@redhat.com>
Michael Jeanson <mjeanson@efficios.com> writes:
> diff --git a/csu/Makefile b/csu/Makefile
> -gen-as-const-headers += rtld-sizes.sym
> +gen-as-const-headers += rtld-sizes.sym rseq-sizes.sym
Ok.
> diff --git a/csu/rseq-sizes.sym b/csu/rseq-sizes.sym
> +#include <stddef.h>
> +
> +--
> +RSEQ_SIZE_SIZE sizeof (unsigned int)
> +RSEQ_SIZE_ALIGN __alignof (unsigned int)
> +
> +RSEQ_OFFSET_SIZE sizeof (ptrdiff_t)
> +RSEQ_OFFSET_ALIGN __alignof (ptrdiff_t)
Ok.
> diff --git a/elf/Makefile b/elf/Makefile
> + dl-rseq-symbols \
Ok.
> diff --git a/elf/dl-rseq-symbols.S b/elf/dl-rseq-symbols.S
> +/* Define symbols used by rseq.
> + 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
> + <https://www.gnu.org/licenses/>. */
> +
> +#include <rseq-sizes.h>
> +#include <sysdep.h>
> +
> +/* Some targets define a macro to denote the zero register. */
> +#undef zero
Ok.
> +/* Define 2 symbols, __rseq_size is public const and _rseq_size, which is an
> + alias of __rseq_size, but hidden and writable for internal use. */
> +
> + .globl __rseq_size
> + .type __rseq_size, %object
> + .size __rseq_size, RSEQ_SIZE_SIZE
> + .hidden _rseq_size
> + .globl _rseq_size
> + .type _rseq_size, %object
> + .size _rseq_size, RSEQ_SIZE_SIZE
> + .section .data.rel.ro
> + .balign RSEQ_SIZE_ALIGN
> +__rseq_size:
> +_rseq_size:
> + .zero RSEQ_SIZE_SIZE
Ok.
> +/* Define 2 symbols, __rseq_offset is public const and _rseq_offset, which is an
> + alias of __rseq_offset, but hidden and writable for internal use. */
> +
> + .globl __rseq_offset
> + .type __rseq_offset, %object
> + .size __rseq_offset, RSEQ_OFFSET_SIZE
> + .hidden _rseq_offset
> + .globl _rseq_offset
> + .type _rseq_offset, %object
> + .size _rseq_offset, RSEQ_OFFSET_SIZE
> + .section .data.rel.ro
> + .balign RSEQ_OFFSET_ALIGN
> +__rseq_offset:
> +_rseq_offset:
> + .zero RSEQ_OFFSET_SIZE
Ok.
> diff --git a/sysdeps/nptl/dl-tls_init_tp.c b/sysdeps/nptl/dl-tls_init_tp.c
> #endif
>
> const unsigned int __rseq_flags;
> -const unsigned int __rseq_size attribute_relro;
> -const ptrdiff_t __rseq_offset attribute_relro;
> +
> +/* The variables are in .data.relro but are not yet write-protected. */
> +extern unsigned int _rseq_size;
> +extern ptrdiff_t _rseq_offset;
Ok.
> @@ -105,10 +107,7 @@ __tls_init_tp (void)
> do_rseq = TUNABLE_GET (rseq, int, NULL);
> if (rseq_register_current_thread (pd, do_rseq))
> {
> - /* We need a writable view of the variables. They are in
> - .data.relro and are not yet write-protected. */
> - extern unsigned int size __asm__ ("__rseq_size");
> - size = sizeof (pd->rseq_area);
> + _rseq_size = sizeof (pd->rseq_area);
> }
Ok.
> @@ -117,8 +116,7 @@ __tls_init_tp (void)
> all targets support __thread_pointer, so set __rseq_offset only
> if the rseq registration may have happened because RSEQ_SIG is
> defined. */
> - extern ptrdiff_t offset __asm__ ("__rseq_offset");
> - offset = (char *) &pd->rseq_area - (char *) __thread_pointer ();
> + _rseq_offset = (char *) &pd->rseq_area - (char *) __thread_pointer ();
> #endif
> }
Ok.
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