06.03.2016 23:10, Andy Lutomirski пишет:
On Sun, Mar 6, 2016 at 12:07 PM, Andy Lutomirski <[email protected]> wrote:
On Mon, Feb 29, 2016 at 1:29 PM, Stas Sergeev <[email protected]> wrote:
This patch implements the SS_AUTODISARM flag that can be ORed with
SS_ONSTACK when forming ss_flags.
When this flag is set, sigaltstack will be disabled when entering
the signal handler; more precisely, after saving sas to uc_stack.
When leaving the signal handler, the sigaltstack is restored by
uc_stack.
When this flag is used, it is safe to switch from sighandler with
swapcontext(). Without this flag, the subsequent signal will corrupt
the state of the switched-away sighandler.
CC: Ingo Molnar <[email protected]>
CC: Peter Zijlstra <[email protected]>
CC: Richard Weinberger <[email protected]>
CC: Andrew Morton <[email protected]>
CC: Oleg Nesterov <[email protected]>
CC: Tejun Heo <[email protected]>
CC: Heinrich Schuchardt <[email protected]>
CC: Jason Low <[email protected]>
CC: Andrea Arcangeli <[email protected]>
CC: Frederic Weisbecker <[email protected]>
CC: Konstantin Khlebnikov <[email protected]>
CC: Josh Triplett <[email protected]>
CC: "Eric W. Biederman" <[email protected]>
CC: Aleksa Sarai <[email protected]>
CC: "Amanieu d'Antras" <[email protected]>
CC: Paul Moore <[email protected]>
CC: Sasha Levin <[email protected]>
CC: Palmer Dabbelt <[email protected]>
CC: Vladimir Davydov <[email protected]>
CC: [email protected]
CC: [email protected]
CC: Andy Lutomirski <[email protected]>
Signed-off-by: Stas Sergeev <[email protected]>
---
include/linux/sched.h | 8 ++++++++
include/linux/signal.h | 4 +++-
include/uapi/linux/signal.h | 3 +++
kernel/fork.c | 2 +-
kernel/signal.c | 23 ++++++++++++-----------
5 files changed, 27 insertions(+), 13 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index a10494a..26201cd 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1587,6 +1587,7 @@ struct task_struct {
unsigned long sas_ss_sp;
size_t sas_ss_size;
+ unsigned sas_ss_flags;
struct callback_head *task_works;
@@ -2573,6 +2574,13 @@ static inline int sas_ss_flags(unsigned long sp)
return on_sig_stack(sp) ? SS_ONSTACK : 0;
}
+static inline void sas_ss_reset(struct task_struct *p)
+{
+ p->sas_ss_sp = 0;
+ p->sas_ss_size = 0;
+ p->sas_ss_flags = SS_DISABLE;
+}
+
static inline unsigned long sigsp(unsigned long sp, struct ksignal *ksig)
{
if (unlikely((ksig->ka.sa.sa_flags & SA_ONSTACK)) && !
sas_ss_flags(sp))
diff --git a/include/linux/signal.h b/include/linux/signal.h
index 92557bb..3fbe814 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -432,8 +432,10 @@ int __save_altstack(stack_t __user *, unsigned long);
stack_t __user *__uss = uss; \
struct task_struct *t = current; \
put_user_ex((void __user *)t->sas_ss_sp, &__uss->ss_sp); \
- put_user_ex(sas_ss_flags(sp), &__uss->ss_flags); \
+ put_user_ex(t->sas_ss_flags, &__uss->ss_flags); \
put_user_ex(t->sas_ss_size, &__uss->ss_size); \
+ if (t->sas_ss_flags & SS_AUTODISARM) \
+ sas_ss_reset(t); \
} while (0);
#ifdef CONFIG_PROC_FS
diff --git a/include/uapi/linux/signal.h b/include/uapi/linux/signal.h
index e1bd50c2..4691bc5 100644
--- a/include/uapi/linux/signal.h
+++ b/include/uapi/linux/signal.h
@@ -6,5 +6,8 @@
#define SS_ONSTACK 1
#define SS_DISABLE 2
+#define SS_VALMASK 0xf
SS_MODE_MASK, perhaps?
Actually, let's invert that.
#define SS_AUTODISARM (1U << 31)
#define SS_FLAG_BITS SS_AUTODISARM
ss_mode = ss_flags & ~SS_FLAG_BITS;
this way flag bits that are currently undefined will continue to trigger EINVAL.
OK, will do.
Though I am still going to keep SS_AUTODISARM =(1 << 4) -
it doesn't matter from what side we add new flags, does it?
