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nptl: clear the whole rseq area before registration

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Due to the extensible nature of the rseq area we can't explictly
initialize fields that are not part of the ABI yet. It was agreed with
upstream that all new fields will be documented as zero initialized by
userspace. Future kernels configured with CONFIG_DEBUG_RSEQ will
validate the content of all fields during registration.

Replace the explicit field initialization with a memset of the whole
rseq area which will cover fields as they are added to future kernels.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
(cherry picked from commit 689a62a4217fae78b9ce0db781dc2a421f2b1ab4)
This commit is contained in:
Michael Jeanson 2025-02-14 13:54:22 -05:00
parent d8e8342369
commit 3e820e17a8
2 changed files with 6 additions and 6 deletions
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1
sysdeps/nptl/dl-tls_init_tp.c
View File

@ -23,6 +23,7 @@
#include <tls.h>
#include <rseq-internal.h>
#include <thread_pointer.h>
#include <dl-symbol-redir-ifunc.h>
#define TUNABLE_NAMESPACE pthread
#include <dl-tunables.h>

11
sysdeps/unix/sysv/linux/rseq-internal.h
View File

@ -52,13 +52,12 @@ rseq_register_current_thread (struct pthread *self, bool do_rseq)
but still expected size 32. */
size = RSEQ_AREA_SIZE_INITIAL;
/* Initialize the rseq fields that are read by the kernel on
registration, there is no guarantee that struct pthread is
cleared on all architectures. */
/* Initialize the whole rseq area to zero prior to registration. */
memset (&self->rseq_area, 0, size);
/* Set the cpu_id field to RSEQ_CPU_ID_UNINITIALIZED, this is checked by
the kernel at registration when CONFIG_DEBUG_RSEQ is enabled. */
THREAD_SETMEM (self, rseq_area.cpu_id, RSEQ_CPU_ID_UNINITIALIZED);
THREAD_SETMEM (self, rseq_area.cpu_id_start, 0);
THREAD_SETMEM (self, rseq_area.rseq_cs, 0);
THREAD_SETMEM (self, rseq_area.flags, 0);
int ret = INTERNAL_SYSCALL_CALL (rseq, &self->rseq_area,
size, 0, RSEQ_SIG);