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| author | Thomas Gleixner <tglx@kernel.org> | 2026-04-28 10:34:45 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2026-05-01 22:32:20 +0300 |
| commit | 010b7723c0a3b9ad58f50b715dbe2e7781d29400 (patch) | |
| tree | 294ceea7cbaf3ca7f411663f74c282a389267234 | |
| parent | e9766e6f7d330dce7530918d8c6e3ec96d6c6e24 (diff) | |
| download | linux-010b7723c0a3b9ad58f50b715dbe2e7781d29400.tar.xz | |
rseq: Don't advertise time slice extensions if disabled
If time slice extensions have been disabled on the kernel command line,
then advertising them in RSEQ flags is wrong.
Adjust the conditionals to reflect reality, fixup the misleading comments
about the gap of these flags and the rseq::flags field.
Fixes: d6200245c75e ("rseq: Allow registering RSEQ with slice extension")
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Link: https://patch.msgid.link/20260428224427.437059375%40kernel.org
Cc: stable@vger.kernel.org
| -rw-r--r-- | include/uapi/linux/rseq.h | 5 | ||||
| -rw-r--r-- | kernel/rseq.c | 9 |
2 files changed, 9 insertions, 5 deletions
diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h index f69344fe6c08..ca6fe1f9d05e 100644 --- a/include/uapi/linux/rseq.h +++ b/include/uapi/linux/rseq.h @@ -28,7 +28,7 @@ enum rseq_cs_flags_bit { RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT = 0, RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT = 1, RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT = 2, - /* (3) Intentional gap to put new bits into a separate byte */ + /* (3) Intentional gap to keep new bits separate */ /* User read only feature flags */ RSEQ_CS_FLAG_SLICE_EXT_AVAILABLE_BIT = 4, @@ -161,6 +161,9 @@ struct rseq { * - RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT * - RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL * - RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE + * + * It is now used for feature status advertisement by the kernel. + * See: enum rseq_cs_flags_bit for further information. */ __u32 flags; diff --git a/kernel/rseq.c b/kernel/rseq.c index b9f11931ef78..586f58f652c6 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -462,10 +462,11 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, int, flags, u32 return -EFAULT; if (IS_ENABLED(CONFIG_RSEQ_SLICE_EXTENSION)) { - rseqfl |= RSEQ_CS_FLAG_SLICE_EXT_AVAILABLE; - if (rseq_slice_extension_enabled() && - (flags & RSEQ_FLAG_SLICE_EXT_DEFAULT_ON)) - rseqfl |= RSEQ_CS_FLAG_SLICE_EXT_ENABLED; + if (rseq_slice_extension_enabled()) { + rseqfl |= RSEQ_CS_FLAG_SLICE_EXT_AVAILABLE; + if (flags & RSEQ_FLAG_SLICE_EXT_DEFAULT_ON) + rseqfl |= RSEQ_CS_FLAG_SLICE_EXT_ENABLED; + } } scoped_user_write_access(rseq, efault) { |