From: Andy Lutomirski <luto@kernel.org>
To: x86@kernel.org, linux-kernel@vger.kernel.org
Cc: "Frédéric Weisbecker" <fweisbec@gmail.com>,
"Rik van Riel" <riel@redhat.com>,
"Oleg Nesterov" <oleg@redhat.com>,
"Denys Vlasenko" <vda.linux@googlemail.com>,
"Borislav Petkov" <bp@alien8.de>,
"Kees Cook" <keescook@chromium.org>,
"Brian Gerst" <brgerst@gmail.com>,
"Andy Lutomirski" <luto@kernel.org>
Subject: [RFC/INCOMPLETE 05/13] x86/entry: Add enter_from_user_mode and use it in syscalls
Date: Tue, 16 Jun 2015 13:16:51 -0700 [thread overview]
Message-ID: <68824568658cb82bca5c2a7a2d171068c3df045d.1434485184.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1434485184.git.luto@kernel.org>
In-Reply-To: <cover.1434485184.git.luto@kernel.org>
Changing the x86 context tracking hooks is dangerous because there
are no good checks that we track our context correctly. Add a
helper to check that we're actually in CONTEXT_USER when we enter
from user mode and wire it up for syscall entries.
Subsequent patches will wire this up for all non-NMI entries as
well. NMIs are their own special beast and cannot currently switch
overall context tracking state. Instead, they have their own
special RCU hooks.
This is a tiny speedup if !CONFIG_CONTEXT_TRACKING (removes a
branch) and a tiny slowdown if CONFIG_CONTEXT_TRACING (adds a layer
of indirection). Eventually, we should fix up the core context
tracking code to supply a function that does what we want (and can
be much simpler than user_exit), which will enable us to get rid of
the extra call.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/entry/common.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 348465473e55..54af0df50080 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -28,6 +28,15 @@
#define CREATE_TRACE_POINTS
#include <trace/events/syscalls.h>
+#ifdef CONFIG_CONTEXT_TRACKING
+/* Called on entry from user mode with IRQs off. */
+asmlinkage __visible void enter_from_user_mode(void)
+{
+ context_tracking_assert_state(CONTEXT_USER);
+ user_exit();
+}
+#endif
+
static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch)
{
#ifdef CONFIG_X86_64
@@ -65,14 +74,16 @@ unsigned long syscall_trace_enter_phase1(struct pt_regs *regs, u32 arch)
work = ACCESS_ONCE(current_thread_info()->flags) &
_TIF_WORK_SYSCALL_ENTRY;
+#ifdef CONFIG_CONTEXT_TRACKING
/*
* If TIF_NOHZ is set, we are required to call user_exit() before
* doing anything that could touch RCU.
*/
if (work & _TIF_NOHZ) {
- user_exit();
+ enter_from_user_mode();
work &= ~_TIF_NOHZ;
}
+#endif
#ifdef CONFIG_SECCOMP
/*
--
2.4.3
next prev parent reply other threads:[~2015-06-16 20:17 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-16 20:16 [RFC/INCOMPLETE 00/13] x86: Rewrite exit-to-userspace code Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 01/13] context_tracking: Add context_tracking_assert_state Andy Lutomirski
2015-06-17 9:41 ` Ingo Molnar
2015-06-17 14:15 ` Andy Lutomirski
2015-06-18 9:57 ` Ingo Molnar
2015-06-18 11:07 ` Andy Lutomirski
2015-06-18 15:52 ` Andy Lutomirski
2015-06-18 16:17 ` Ingo Molnar
2015-06-18 16:26 ` Frederic Weisbecker
2015-06-18 19:26 ` Andy Lutomirski
2015-06-17 15:27 ` Paul E. McKenney
2015-06-18 9:59 ` Ingo Molnar
2015-06-18 22:54 ` Paul E. McKenney
2015-06-19 2:19 ` Paul E. McKenney
2015-06-30 11:04 ` Ingo Molnar
2015-06-30 16:16 ` Paul E. McKenney
2015-06-16 20:16 ` [RFC/INCOMPLETE 02/13] notifiers: Assert that RCU is watching in notify_die Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 03/13] x86: Move C entry and exit code to arch/x86/entry/common.c Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 04/13] x86/traps: Assert that we're in CONTEXT_KERNEL in exception entries Andy Lutomirski
2015-06-16 20:16 ` Andy Lutomirski [this message]
2015-06-16 20:16 ` [RFC/INCOMPLETE 06/13] x86/entry: Add new, comprehensible entry and exit hooks Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 07/13] x86/entry/64: Really create an error-entry-from-usermode code path Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 08/13] x86/entry/64: Migrate 64-bit syscalls to new exit hooks Andy Lutomirski
2015-06-17 10:00 ` Ingo Molnar
2015-06-17 10:02 ` Ingo Molnar
2015-06-17 14:12 ` Andy Lutomirski
2015-06-18 10:17 ` Ingo Molnar
2015-06-18 10:19 ` Ingo Molnar
2015-06-16 20:16 ` [RFC/INCOMPLETE 09/13] x86/entry/compat: Migrate compat " Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 10/13] x86/asm/entry/64: Save all regs on interrupt entry Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 11/13] x86/asm/entry/64: Simplify irq stack pt_regs handling Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 12/13] x86/asm/entry/64: Migrate error and interrupt exit work to C Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 13/13] x86/entry: Remove SCHEDULE_USER and asm/context-tracking.h Andy Lutomirski
2015-06-17 9:48 ` [RFC/INCOMPLETE 00/13] x86: Rewrite exit-to-userspace code Ingo Molnar
2015-06-17 10:13 ` Richard Weinberger
2015-06-17 11:04 ` Ingo Molnar
2015-06-17 14:19 ` Andy Lutomirski
2015-06-17 15:16 ` Andy Lutomirski
2015-06-18 10:14 ` Ingo Molnar
2015-06-17 10:32 ` Ingo Molnar
2015-06-17 11:14 ` Ingo Molnar
2015-06-17 14:23 ` Andy Lutomirski
2015-06-18 10:11 ` Ingo Molnar
2015-06-18 11:06 ` Andy Lutomirski
2015-06-18 16:24 ` Ingo Molnar
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