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authorMathieu Desnoyers <mathieu.desnoyers@efficios.com>2022-06-22 15:46:16 -0400
committerIngo Molnar <mingo@kernel.org>2022-08-01 15:21:29 +0200
commit0190e4198e47fe99d002d72588f34fd62c9ab570 (patch)
tree025ffe0425ab8aa28c0ded5bc3ca61a79019f605 /kernel/rseq.c
parent91caa5ae242465c3ab9fd473e50170faa7e944f4 (diff)
rseq: Deprecate RSEQ_CS_FLAG_NO_RESTART_ON_* flags
The pretty much unused RSEQ_CS_FLAG_NO_RESTART_ON_* flags introduce complexity in rseq, and are subtly buggy [1]. Solving those issues requires introducing additional complexity in the rseq implementation for each supported architecture. Considering that it complexifies the rseq ABI, I am proposing that we deprecate those flags. [2] So far there appears to be consensus from maintainers of user-space projects impacted by this feature that its removal would be a welcome simplification. [3] The deprecation approach proposed here is to issue WARN_ON_ONCE() when encountering those flags and kill the offending process with sigsegv. This should allow us to quickly identify whether anyone yells at us for removing this. Link: https://lore.kernel.org/lkml/20220618182515.95831-1-minhquangbui99@gmail.com/ [1] Link: https://lore.kernel.org/lkml/258546133.12151.1655739550814.JavaMail.zimbra@efficios.com/ [2] Link: https://lore.kernel.org/lkml/87pmj1enjh.fsf@email.froward.int.ebiederm.org/ [3] Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/lkml/20220622194617.1155957-1-mathieu.desnoyers@efficios.com
Diffstat (limited to 'kernel/rseq.c')
-rw-r--r--kernel/rseq.c23
1 files changed, 8 insertions, 15 deletions
diff --git a/kernel/rseq.c b/kernel/rseq.c
index 97ac20b4f738..81d7dc80787b 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -18,8 +18,9 @@
#define CREATE_TRACE_POINTS
#include <trace/events/rseq.h>
-#define RSEQ_CS_PREEMPT_MIGRATE_FLAGS (RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE | \
- RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT)
+#define RSEQ_CS_NO_RESTART_FLAGS (RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT | \
+ RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL | \
+ RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE)
/*
*
@@ -175,23 +176,15 @@ static int rseq_need_restart(struct task_struct *t, u32 cs_flags)
u32 flags, event_mask;
int ret;
+ if (WARN_ON_ONCE(cs_flags & RSEQ_CS_NO_RESTART_FLAGS))
+ return -EINVAL;
+
/* Get thread flags. */
ret = get_user(flags, &t->rseq->flags);
if (ret)
return ret;
- /* Take critical section flags into account. */
- flags |= cs_flags;
-
- /*
- * Restart on signal can only be inhibited when restart on
- * preempt and restart on migrate are inhibited too. Otherwise,
- * a preempted signal handler could fail to restart the prior
- * execution context on sigreturn.
- */
- if (unlikely((flags & RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL) &&
- (flags & RSEQ_CS_PREEMPT_MIGRATE_FLAGS) !=
- RSEQ_CS_PREEMPT_MIGRATE_FLAGS))
+ if (WARN_ON_ONCE(flags & RSEQ_CS_NO_RESTART_FLAGS))
return -EINVAL;
/*
@@ -203,7 +196,7 @@ static int rseq_need_restart(struct task_struct *t, u32 cs_flags)
t->rseq_event_mask = 0;
preempt_enable();
- return !!(event_mask & ~flags);
+ return !!event_mask;
}
static int clear_rseq_cs(struct task_struct *t)