[PATCH v3 3/3] Linux: Add tests that check that TLS and rseq area are separate
Michael Jeanson
mjeanson@efficios.com
Wed Jan 15 16:11:09 GMT 2025
On 2025-01-15 10:46, Florian Weimer wrote:
> The new test elf/tst-rseq-tls-range-4096-static reliably detected
> the extra TLS allocation problem (tcb_offset was dropped from
> the allocation size) on aarch64. It also failed with a crash
> in dlopen *before* the extra TLS changes, so TLS alignment with
> static dlopen was already broken.
LGTM, thanks.
Reviewed-by: Michael Jeanson <mjeanson@efficios.com>
> ---
> v3: Adjust __rseq_size to at least 32, multiples of 32.
> sysdeps/unix/sysv/linux/Makefile | 14 ++
> .../linux/tst-rseq-tls-range-4096-static.c | 1 +
> .../unix/sysv/linux/tst-rseq-tls-range-4096.c | 1 +
> .../unix/sysv/linux/tst-rseq-tls-range-mod.c | 1 +
> .../sysv/linux/tst-rseq-tls-range-static.c | 1 +
> sysdeps/unix/sysv/linux/tst-rseq-tls-range.c | 195 ++++++++++++++++++
> 6 files changed, 213 insertions(+)
> create mode 100644 sysdeps/unix/sysv/linux/tst-rseq-tls-range-4096-static.c
> create mode 100644 sysdeps/unix/sysv/linux/tst-rseq-tls-range-4096.c
> create mode 100644 sysdeps/unix/sysv/linux/tst-rseq-tls-range-mod.c
> create mode 100644 sysdeps/unix/sysv/linux/tst-rseq-tls-range-static.c
> create mode 100644 sysdeps/unix/sysv/linux/tst-rseq-tls-range.c
>
> diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
> index c8d30cc405..395d2d6593 100644
> --- a/sysdeps/unix/sysv/linux/Makefile
> +++ b/sysdeps/unix/sysv/linux/Makefile
> @@ -660,6 +660,20 @@ install-bin += \
>
> $(objpfx)pldd: $(objpfx)xmalloc.o
>
> +tests += tst-rseq-tls-range tst-rseq-tls-range-4096
> +tests-static += tst-rseq-tls-range-static tst-rseq-tls-range-4096-static
> +modules-names += tst-rseq-tls-range-mod
> +CFLAGS-tst-rseq-tls-range.c += -DMAIN_TLS_ALIGN=4
> +CFLAGS-tst-rseq-tls-range-4096.c += -DMAIN_TLS_ALIGN=4096
> +CFLAGS-tst-rseq-tls-range-static.c += -DMAIN_TLS_ALIGN=4
> +CFLAGS-tst-rseq-tls-range-4096-static.c += -DMAIN_TLS_ALIGN=4096
> +$(objpfx)tst-rseq-tls-range.out: $(objpfx)tst-rseq-tls-range-mod.so
> +$(objpfx)tst-rseq-tls-range-4096.out: $(objpfx)tst-rseq-tls-range-mod.so
> +$(objpfx)tst-rseq-tls-range-static.out: $(objpfx)tst-rseq-tls-range-mod.so
> +$(objpfx)tst-rseq-tls-range-4096-static.out: $(objpfx)tst-rseq-tls-range-mod.so
> +tst-rseq-tls-range-static-ENV = LD_LIBRARY_PATH=$(objpfx):$(common-objpfx)
> +tst-rseq-tls-range-4096-static-ENV = LD_LIBRARY_PATH=$(objpfx):$(common-objpfx)
> +
> test-internal-extras += tst-nolink-libc
> ifeq ($(run-built-tests),yes)
> tests-special += \
> diff --git a/sysdeps/unix/sysv/linux/tst-rseq-tls-range-4096-static.c b/sysdeps/unix/sysv/linux/tst-rseq-tls-range-4096-static.c
> new file mode 100644
> index 0000000000..5ad2853847
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/tst-rseq-tls-range-4096-static.c
> @@ -0,0 +1 @@
> +#include "tst-rseq-tls-range.c"
> diff --git a/sysdeps/unix/sysv/linux/tst-rseq-tls-range-4096.c b/sysdeps/unix/sysv/linux/tst-rseq-tls-range-4096.c
> new file mode 100644
> index 0000000000..5ad2853847
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/tst-rseq-tls-range-4096.c
> @@ -0,0 +1 @@
> +#include "tst-rseq-tls-range.c"
> diff --git a/sysdeps/unix/sysv/linux/tst-rseq-tls-range-mod.c b/sysdeps/unix/sysv/linux/tst-rseq-tls-range-mod.c
> new file mode 100644
> index 0000000000..165e468eaa
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/tst-rseq-tls-range-mod.c
> @@ -0,0 +1 @@
> +__thread int mod_thread_var __attribute__ ((tls_model ("initial-exec")));
> diff --git a/sysdeps/unix/sysv/linux/tst-rseq-tls-range-static.c b/sysdeps/unix/sysv/linux/tst-rseq-tls-range-static.c
> new file mode 100644
> index 0000000000..5ad2853847
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/tst-rseq-tls-range-static.c
> @@ -0,0 +1 @@
> +#include "tst-rseq-tls-range.c"
> diff --git a/sysdeps/unix/sysv/linux/tst-rseq-tls-range.c b/sysdeps/unix/sysv/linux/tst-rseq-tls-range.c
> new file mode 100644
> index 0000000000..5891e5f97f
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/tst-rseq-tls-range.c
> @@ -0,0 +1,195 @@
> +/* Verify that TLS blocks and the rseq area do not overlap.
> + Copyright (C) 2025 Free Software Foundation, Inc.
> +
> + 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 <array_length.h>
> +#include <elf.h>
> +#include <link.h>
> +#include <stdbool.h>
> +#include <stdint.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <support/check.h>
> +#include <support/xdlfcn.h>
> +#include <sys/auxv.h>
> +#include <sys/param.h>
> +#include <sys/rseq.h>
> +#include <thread_pointer.h>
> +#include <unistd.h>
> +
> +/* Used to keep track of address ranges. The ranges are sorted and
> + then checked for overlap. */
> +
> +struct address_range
> +{
> + const char *prefix;
> + const char *label;
> + uintptr_t start;
> + size_t length;
> +};
> +
> +struct address_range ranges[20];
> +size_t range_count;
> +
> +static void
> +add_range (const char *prefix, const char *label,
> + const void *start, size_t length)
> +{
> + TEST_VERIFY (start != NULL);
> + TEST_VERIFY (length > 0);
> + TEST_VERIFY_EXIT (range_count < array_length (ranges));
> + ranges[range_count].prefix = prefix;
> + ranges[range_count].label = label;
> + ranges[range_count].start = (uintptr_t) start;
> + ranges[range_count].length = length;
> + ++range_count;
> +}
> +
> +static int
> +range_compare (const void *a1, const void *b1)
> +{
> + const struct address_range *a = a1;
> + const struct address_range *b = b1;
> + if (a->start < b->start)
> + return -1;
> + if (a->start > b->start)
> + return 1;
> + return 0;
> +}
> +
> +static void
> +check_for_overlap (void)
> +{
> + qsort (ranges, range_count, sizeof (ranges[0]), range_compare);
> + uintptr_t previous_end = ranges[0].start + ranges[0].length - 1;
> + for (size_t i = 1; i < range_count; ++i)
> + {
> + uintptr_t this_end = ranges[i].start + ranges[i].length - 1;
> + if (ranges[i].start <= previous_end)
> + {
> + puts ("error: overlap between address ranges");
> + printf (" %s%s: [0x%lx, 0x%lx)\n",
> + ranges[i - 1].prefix, ranges[i - 1].label,
> + (unsigned long int) ranges[i - 1].start,
> + (unsigned long int) previous_end);
> + printf (" %s%s: [0x%lx, 0x%lx)\n",
> + ranges[i].prefix, ranges[i].label,
> + (unsigned long int) ranges[i].start,
> + (unsigned long int) this_end);
> + }
> + previous_end = this_end;
> + }
> +}
> +
> +static void
> +add_rseq (void)
> +{
> + /* The initial size of 32 bytes is always allocated. The value
> + reported by __rseq_size does not include the alignment, which can
> + be larger than 32 if requested by the kernel through the
> + auxiliary vector. */
> + size_t size = 32;
> + if (__rseq_size > 0)
> + size = roundup (__rseq_size, MAX (getauxval (AT_RSEQ_ALIGN), 32));
> +
> + printf ("info: adding rseq area of %zu bytes\n", size);
> + add_range ("", "rseq area",
> + (char *) __thread_pointer () + __rseq_offset, size);
> +}
> +
> +/* These functions add the TLS data for all loaded modules to the
> + recorded address ranges. */
> +
> +static int
> +dlip_callback (struct dl_phdr_info *info, size_t size, void *ignored)
> +{
> + /* If the dynamic linker does not provide TLS address information,
> + there is nothing to register. */
> + if (info->dlpi_tls_data == NULL)
> + return 0;
> +
> + for (int i = 0; i < info->dlpi_phnum; ++i)
> + {
> + if (info->dlpi_phdr[i].p_type == PT_TLS)
> + {
> + printf ("info: adding TLS range for \"%s\" (%zu bytes)\n",
> + info->dlpi_name, (size_t) info->dlpi_phdr[i].p_memsz);
> + add_range ("TLS for ",
> + info->dlpi_name[0] != '\0' ? info->dlpi_name : "main",
> + info->dlpi_tls_data, info->dlpi_phdr[i].p_memsz);
> + break;
> + }
> + }
> + return 0;
> +}
> +
> +/* Returns true if any TLS ranges were found. */
> +static void
> +add_tls_ranges (void)
> +{
> + dl_iterate_phdr (dlip_callback, NULL);
> +}
> +
> +volatile __thread int thread_var __attribute__ ((aligned (MAIN_TLS_ALIGN)));
> +
> +static int
> +do_test (void)
> +{
> + void *original_brk = sbrk (0);
> + void *initial_allocation = malloc (16);
> +
> + /* Ensure that the variable is not optimized away. */
> + thread_var = 0;
> +
> + printf ("info: rseq area size: %u\n", __rseq_size);
> +
> + puts ("info: checking address ranges with initially loaded modules");
> + add_range ("", "program break", original_brk, 1);
> + add_range ("", "malloc allocation", initial_allocation, 16);
> + add_rseq ();
> + add_tls_ranges ();
> + printf ("info: %zu ranges found\n", range_count);
> + check_for_overlap ();
> + range_count = 0;
> +
> + puts ("info: checking address ranges after dlopen");
> + void *handle = xdlopen ("tst-rseq-tls-range-mod.so", RTLD_NOW);
> + int *mod_thread_var = xdlsym (handle, "mod_thread_var");
> + add_range ("", "program break", original_brk, 1);
> + add_range ("", "malloc allocation", initial_allocation, 16);
> + add_rseq ();
> + add_tls_ranges ();
> + {
> + bool found_objects = false;
> + for (size_t i = 0; i < range_count; ++i)
> + if (strchr (ranges[i].label, '/') != NULL)
> + found_objects = true;
> + if (!found_objects)
> + /* __tls_get_addr does not fully work with static dlopen.
> + Add some fall-back test data. */
> + add_range ("", "mod_thread_var",
> + mod_thread_var, sizeof (*mod_thread_var));
> + }
> + printf ("info: %zu ranges found\n", range_count);
> + check_for_overlap ();
> + xdlclose (handle);
> +
> + free (initial_allocation);
> + return 0;
> +}
> +
> +#include <support/test-driver.c>
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