x86/entry: Remove exception_enter() from most trap handlers
On 64-bit kernels, we don't need it any more: we handle context
tracking directly on entry from user mode and exit to user mode.
On 32-bit kernels, we don't support context tracking at all, so
these callbacks had no effect.
Note: this doesn't change do_page_fault(). Before we do that,
we need to make sure that there is no code that can page fault
from kernel mode with CONTEXT_USER. The 32-bit fast system call
stack argument code is the only offender I'm aware of right now.
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/ae22f4dfebd799c916574089964592be218151f9.1435952415.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 2a783c4..8e65d8a 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -108,13 +108,10 @@
preempt_count_dec();
}
-enum ctx_state ist_enter(struct pt_regs *regs)
+void ist_enter(struct pt_regs *regs)
{
- enum ctx_state prev_state;
-
if (user_mode(regs)) {
- /* Other than that, we're just an exception. */
- prev_state = exception_enter();
+ CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
} else {
/*
* We might have interrupted pretty much anything. In
@@ -123,32 +120,25 @@
* but we need to notify RCU.
*/
rcu_nmi_enter();
- prev_state = CONTEXT_KERNEL; /* the value is irrelevant. */
}
/*
- * We are atomic because we're on the IST stack (or we're on x86_32,
- * in which case we still shouldn't schedule).
- *
- * This must be after exception_enter(), because exception_enter()
- * won't do anything if in_interrupt() returns true.
+ * We are atomic because we're on the IST stack; or we're on
+ * x86_32, in which case we still shouldn't schedule; or we're
+ * on x86_64 and entered from user mode, in which case we're
+ * still atomic unless ist_begin_non_atomic is called.
*/
preempt_count_add(HARDIRQ_OFFSET);
/* This code is a bit fragile. Test it. */
rcu_lockdep_assert(rcu_is_watching(), "ist_enter didn't work");
-
- return prev_state;
}
-void ist_exit(struct pt_regs *regs, enum ctx_state prev_state)
+void ist_exit(struct pt_regs *regs)
{
- /* Must be before exception_exit. */
preempt_count_sub(HARDIRQ_OFFSET);
- if (user_mode(regs))
- return exception_exit(prev_state);
- else
+ if (!user_mode(regs))
rcu_nmi_exit();
}
@@ -162,7 +152,7 @@
* a double fault, it can be safe to schedule. ist_begin_non_atomic()
* begins a non-atomic section within an ist_enter()/ist_exit() region.
* Callers are responsible for enabling interrupts themselves inside
- * the non-atomic section, and callers must call is_end_non_atomic()
+ * the non-atomic section, and callers must call ist_end_non_atomic()
* before ist_exit().
*/
void ist_begin_non_atomic(struct pt_regs *regs)
@@ -289,7 +279,6 @@
static void do_error_trap(struct pt_regs *regs, long error_code, char *str,
unsigned long trapnr, int signr)
{
- enum ctx_state prev_state = exception_enter();
siginfo_t info;
CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
@@ -300,8 +289,6 @@
do_trap(trapnr, signr, str, regs, error_code,
fill_trap_info(regs, signr, trapnr, &info));
}
-
- exception_exit(prev_state);
}
#define DO_ERROR(trapnr, signr, str, name) \
@@ -353,7 +340,7 @@
}
#endif
- ist_enter(regs); /* Discard prev_state because we won't return. */
+ ist_enter(regs);
notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_DF, SIGSEGV);
tsk->thread.error_code = error_code;
@@ -373,15 +360,13 @@
dotraplinkage void do_bounds(struct pt_regs *regs, long error_code)
{
- enum ctx_state prev_state;
const struct bndcsr *bndcsr;
siginfo_t *info;
- prev_state = exception_enter();
CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
if (notify_die(DIE_TRAP, "bounds", regs, error_code,
X86_TRAP_BR, SIGSEGV) == NOTIFY_STOP)
- goto exit;
+ return;
conditional_sti(regs);
if (!user_mode(regs))
@@ -438,9 +423,8 @@
die("bounds", regs, error_code);
}
-exit:
- exception_exit(prev_state);
return;
+
exit_trap:
/*
* This path out is for all the cases where we could not
@@ -450,36 +434,33 @@
* time..
*/
do_trap(X86_TRAP_BR, SIGSEGV, "bounds", regs, error_code, NULL);
- exception_exit(prev_state);
}
dotraplinkage void
do_general_protection(struct pt_regs *regs, long error_code)
{
struct task_struct *tsk;
- enum ctx_state prev_state;
- prev_state = exception_enter();
CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
conditional_sti(regs);
if (v8086_mode(regs)) {
local_irq_enable();
handle_vm86_fault((struct kernel_vm86_regs *) regs, error_code);
- goto exit;
+ return;
}
tsk = current;
if (!user_mode(regs)) {
if (fixup_exception(regs))
- goto exit;
+ return;
tsk->thread.error_code = error_code;
tsk->thread.trap_nr = X86_TRAP_GP;
if (notify_die(DIE_GPF, "general protection fault", regs, error_code,
X86_TRAP_GP, SIGSEGV) != NOTIFY_STOP)
die("general protection fault", regs, error_code);
- goto exit;
+ return;
}
tsk->thread.error_code = error_code;
@@ -495,16 +476,12 @@
}
force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);
-exit:
- exception_exit(prev_state);
}
NOKPROBE_SYMBOL(do_general_protection);
/* May run on IST stack. */
dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
{
- enum ctx_state prev_state;
-
#ifdef CONFIG_DYNAMIC_FTRACE
/*
* ftrace must be first, everything else may cause a recursive crash.
@@ -517,7 +494,7 @@
if (poke_int3_handler(regs))
return;
- prev_state = ist_enter(regs);
+ ist_enter(regs);
CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
#ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,
@@ -544,7 +521,7 @@
preempt_conditional_cli(regs);
debug_stack_usage_dec();
exit:
- ist_exit(regs, prev_state);
+ ist_exit(regs);
}
NOKPROBE_SYMBOL(do_int3);
@@ -620,12 +597,11 @@
dotraplinkage void do_debug(struct pt_regs *regs, long error_code)
{
struct task_struct *tsk = current;
- enum ctx_state prev_state;
int user_icebp = 0;
unsigned long dr6;
int si_code;
- prev_state = ist_enter(regs);
+ ist_enter(regs);
get_debugreg(dr6, 6);
@@ -700,7 +676,7 @@
debug_stack_usage_dec();
exit:
- ist_exit(regs, prev_state);
+ ist_exit(regs);
}
NOKPROBE_SYMBOL(do_debug);
@@ -752,23 +728,15 @@
dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code)
{
- enum ctx_state prev_state;
-
- prev_state = exception_enter();
CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
math_error(regs, error_code, X86_TRAP_MF);
- exception_exit(prev_state);
}
dotraplinkage void
do_simd_coprocessor_error(struct pt_regs *regs, long error_code)
{
- enum ctx_state prev_state;
-
- prev_state = exception_enter();
CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
math_error(regs, error_code, X86_TRAP_XF);
- exception_exit(prev_state);
}
dotraplinkage void
@@ -780,9 +748,6 @@
dotraplinkage void
do_device_not_available(struct pt_regs *regs, long error_code)
{
- enum ctx_state prev_state;
-
- prev_state = exception_enter();
CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
BUG_ON(use_eager_fpu());
@@ -794,7 +759,6 @@
info.regs = regs;
math_emulate(&info);
- exception_exit(prev_state);
return;
}
#endif
@@ -802,7 +766,6 @@
#ifdef CONFIG_X86_32
conditional_sti(regs);
#endif
- exception_exit(prev_state);
}
NOKPROBE_SYMBOL(do_device_not_available);
@@ -810,9 +773,7 @@
dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code)
{
siginfo_t info;
- enum ctx_state prev_state;
- prev_state = exception_enter();
CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
local_irq_enable();
@@ -825,7 +786,6 @@
do_trap(X86_TRAP_IRET, SIGILL, "iret exception", regs, error_code,
&info);
}
- exception_exit(prev_state);
}
#endif