diff options
| author | Andy Lutomirski <luto@kernel.org> | 2015-07-03 19:44:25 (GMT) |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-07-07 08:59:06 (GMT) |
| commit | feed36cde0a10adb957445a37e48f957f30b2273 (patch) | |
| tree | 9d857a06a31e8ce1070d15e9bd046a50a0d09cde /arch/x86/entry | |
| parent | 02fdcd5eac9d653d1addbd69b0c58d73650e1c00 (diff) | |
| download | linux-feed36cde0a10adb957445a37e48f957f30b2273.tar.xz | |
x86/entry: Add enter_from_user_mode() and use it in syscalls
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>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: paulmck@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/853b42420066ec3fb856779cdc223a6dcb5d355b.1435952415.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/entry')
| -rw-r--r-- | arch/x86/entry/common.c | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 917d0c3..9a327ee 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. */ +__visible void enter_from_user_mode(void) +{ + CT_WARN_ON(ct_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 /* |