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x86/entry/traps: Refactor preemption and interrupt flag handling
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Make the preemption and interrupt flag handling more readable by
removing preempt_conditional_sti() and preempt_conditional_cli()
helpers and using preempt_disable() and
preempt_enable_no_resched() instead.

Rename contitional_sti() and conditional_cli() to the more
understandable cond_local_irq_enable() and
cond_local_irq_disable() respectively, while at it.

Suggested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com>
[ Boris: massage text. ]
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1453750913-4781-2-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Alexander Kuleshov authored and Ingo Molnar committed Feb 1, 2016
1 parent bb56968 commit d99e1bd
Showing 1 changed file with 19 additions and 28 deletions.
47 changes: 19 additions & 28 deletions arch/x86/kernel/traps.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -83,30 +83,16 @@ gate_desc idt_table[NR_VECTORS] __page_aligned_bss;
DECLARE_BITMAP(used_vectors, NR_VECTORS);
EXPORT_SYMBOL_GPL(used_vectors);

static inline void conditional_sti(struct pt_regs *regs)
static inline void cond_local_irq_enable(struct pt_regs *regs)
{
if (regs->flags & X86_EFLAGS_IF)
local_irq_enable();
}

static inline void preempt_conditional_sti(struct pt_regs *regs)
{
preempt_count_inc();
if (regs->flags & X86_EFLAGS_IF)
local_irq_enable();
}

static inline void conditional_cli(struct pt_regs *regs)
{
if (regs->flags & X86_EFLAGS_IF)
local_irq_disable();
}

static inline void preempt_conditional_cli(struct pt_regs *regs)
static inline void cond_local_irq_disable(struct pt_regs *regs)
{
if (regs->flags & X86_EFLAGS_IF)
local_irq_disable();
preempt_count_dec();
}

void ist_enter(struct pt_regs *regs)
Expand Down Expand Up @@ -286,7 +272,7 @@ static void do_error_trap(struct pt_regs *regs, long error_code, char *str,

if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) !=
NOTIFY_STOP) {
conditional_sti(regs);
cond_local_irq_enable(regs);
do_trap(trapnr, signr, str, regs, error_code,
fill_trap_info(regs, signr, trapnr, &info));
}
Expand Down Expand Up @@ -368,7 +354,7 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code)
if (notify_die(DIE_TRAP, "bounds", regs, error_code,
X86_TRAP_BR, SIGSEGV) == NOTIFY_STOP)
return;
conditional_sti(regs);
cond_local_irq_enable(regs);

if (!user_mode(regs))
die("bounds", regs, error_code);
Expand Down Expand Up @@ -443,7 +429,7 @@ do_general_protection(struct pt_regs *regs, long error_code)
struct task_struct *tsk;

RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
conditional_sti(regs);
cond_local_irq_enable(regs);

if (v8086_mode(regs)) {
local_irq_enable();
Expand Down Expand Up @@ -517,9 +503,11 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
* as we may switch to the interrupt stack.
*/
debug_stack_usage_inc();
preempt_conditional_sti(regs);
preempt_disable();
cond_local_irq_enable(regs);
do_trap(X86_TRAP_BP, SIGTRAP, "int3", regs, error_code, NULL);
preempt_conditional_cli(regs);
cond_local_irq_disable(regs);
preempt_enable_no_resched();
debug_stack_usage_dec();
exit:
ist_exit(regs);
Expand Down Expand Up @@ -648,12 +636,14 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code)
debug_stack_usage_inc();

/* It's safe to allow irq's after DR6 has been saved */
preempt_conditional_sti(regs);
preempt_disable();
cond_local_irq_enable(regs);

if (v8086_mode(regs)) {
handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code,
X86_TRAP_DB);
preempt_conditional_cli(regs);
cond_local_irq_disable(regs);
preempt_enable_no_resched();
debug_stack_usage_dec();
goto exit;
}
Expand All @@ -673,7 +663,8 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code)
si_code = get_si_code(tsk->thread.debugreg6);
if (tsk->thread.debugreg6 & (DR_STEP | DR_TRAP_BITS) || user_icebp)
send_sigtrap(tsk, regs, error_code, si_code);
preempt_conditional_cli(regs);
cond_local_irq_disable(regs);
preempt_enable_no_resched();
debug_stack_usage_dec();

exit:
Expand All @@ -696,7 +687,7 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr)

if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, SIGFPE) == NOTIFY_STOP)
return;
conditional_sti(regs);
cond_local_irq_enable(regs);

if (!user_mode(regs)) {
if (!fixup_exception(regs)) {
Expand Down Expand Up @@ -743,7 +734,7 @@ do_simd_coprocessor_error(struct pt_regs *regs, long error_code)
dotraplinkage void
do_spurious_interrupt_bug(struct pt_regs *regs, long error_code)
{
conditional_sti(regs);
cond_local_irq_enable(regs);
}

dotraplinkage void
Expand All @@ -756,7 +747,7 @@ do_device_not_available(struct pt_regs *regs, long error_code)
if (read_cr0() & X86_CR0_EM) {
struct math_emu_info info = { };

conditional_sti(regs);
cond_local_irq_enable(regs);

info.regs = regs;
math_emulate(&info);
Expand All @@ -765,7 +756,7 @@ do_device_not_available(struct pt_regs *regs, long error_code)
#endif
fpu__restore(&current->thread.fpu); /* interrupts still off */
#ifdef CONFIG_X86_32
conditional_sti(regs);
cond_local_irq_enable(regs);
#endif
}
NOKPROBE_SYMBOL(do_device_not_available);
Expand Down

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