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Date: Tue, 05 May 2020 15:49:45 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: x86@...nel.org, "Paul E. McKenney" <paulmck@...nel.org>,
Andy Lutomirski <luto@...nel.org>,
Alexandre Chartre <alexandre.chartre@...cle.com>,
Frederic Weisbecker <frederic@...nel.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <sean.j.christopherson@...el.com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Petr Mladek <pmladek@...e.com>,
Steven Rostedt <rostedt@...dmis.org>,
Joel Fernandes <joel@...lfernandes.org>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Juergen Gross <jgross@...e.com>,
Brian Gerst <brgerst@...il.com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Will Deacon <will@...nel.org>
Subject: [patch V4 part 4 19/24] x86/entry: Implement user mode C entry points
for #DB and #MCE
The MCE entry point uses the same mechanism as the IST entry point for
now. For #DB split the inner workings and just keep the ist_enter/exit
magic in the IST variant. Fixup the ASM code to emit the proper
noist_##cfunc call.
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
arch/x86/entry/entry_64.S | 2 -
arch/x86/kernel/cpu/mce/core.c | 40 +++++++++++++++++++----
arch/x86/kernel/traps.c | 70 +++++++++++++++++++++++++++++++----------
3 files changed, 88 insertions(+), 24 deletions(-)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -658,7 +658,7 @@ SYM_CODE_START(\asmsym)
/* Switch to the regular task stack and use the noist entry point */
.Lfrom_usermode_switch_stack_\@:
- idtentry_body vector \cfunc, has_error_code=0
+ idtentry_body vector noist_\cfunc, has_error_code=0 sane=1
_ASM_NOKPROBE(\asmsym)
SYM_CODE_END(\asmsym)
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1904,24 +1904,50 @@ static void unexpected_machine_check(str
/* Call the installed machine check handler for this CPU setup. */
void (*machine_check_vector)(struct pt_regs *) = unexpected_machine_check;
-DEFINE_IDTENTRY_MCE(exc_machine_check)
+static __always_inline void exc_machine_check_kernel(struct pt_regs *regs)
{
+ /*
+ * Only required when from kernel mode. See
+ * mce_check_crashing_cpu() for details.
+ */
if (machine_check_vector == do_machine_check &&
mce_check_crashing_cpu())
return;
- if (user_mode(regs))
- idtentry_enter(regs);
- else
- nmi_enter();
+ nmi_enter();
+ machine_check_vector(regs);
+ nmi_exit();
+}
+static __always_inline void exc_machine_check_user(struct pt_regs *regs)
+{
+ idtentry_enter(regs);
machine_check_vector(regs);
+ idtentry_exit(regs);
+}
+#ifdef CONFIG_X86_64
+/* MCE hit kernel mode */
+DEFINE_IDTENTRY_MCE(exc_machine_check)
+{
+ exc_machine_check_kernel(regs);
+}
+
+/* The user mode variant. */
+DEFINE_IDTENTRY_MCE_USER(exc_machine_check)
+{
+ exc_machine_check_user(regs);
+}
+#else
+/* 32bit unified entry point */
+DEFINE_IDTENTRY_MCE(exc_machine_check)
+{
if (user_mode(regs))
- idtentry_exit(regs);
+ exc_machine_check_user(regs);
else
- nmi_exit();
+ exc_machine_check_kernel(regs);
}
+#endif
/*
* Called for each booted CPU to set up machine checks.
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -753,20 +753,12 @@ static __always_inline void debug_exit(u
*
* May run on IST stack.
*/
-DEFINE_IDTENTRY_DEBUG(exc_debug)
+static noinstr void handle_debug(struct pt_regs *regs, unsigned long dr6)
{
struct task_struct *tsk = current;
- unsigned long dr6, dr7;
int user_icebp = 0;
int si_code;
- debug_enter(&dr6, &dr7);
-
- if (user_mode(regs))
- idtentry_enter(regs);
- else
- nmi_enter();
-
/*
* The SDM says "The processor clears the BTF flag when it
* generates a debug exception." Clear TIF_BLOCKSTEP to keep
@@ -778,7 +770,7 @@ DEFINE_IDTENTRY_DEBUG(exc_debug)
is_sysenter_singlestep(regs))) {
dr6 &= ~DR_STEP;
if (!dr6)
- goto exit;
+ return;
/*
* else we might have gotten a single-step trap and hit a
* watchpoint at the same time, in which case we should fall
@@ -799,12 +791,12 @@ DEFINE_IDTENTRY_DEBUG(exc_debug)
#ifdef CONFIG_KPROBES
if (kprobe_debug_handler(regs))
- goto exit;
+ return;
#endif
if (notify_die(DIE_DEBUG, "debug", regs, (long)&dr6, 0,
SIGTRAP) == NOTIFY_STOP)
- goto exit;
+ return;
/*
* Let others (NMI) know that the debug stack is in use
@@ -820,7 +812,7 @@ DEFINE_IDTENTRY_DEBUG(exc_debug)
X86_TRAP_DB);
cond_local_irq_disable(regs);
debug_stack_usage_dec();
- goto exit;
+ return;
}
if (WARN_ON_ONCE((dr6 & DR_STEP) && !user_mode(regs))) {
@@ -839,14 +831,60 @@ DEFINE_IDTENTRY_DEBUG(exc_debug)
send_sigtrap(regs, 0, si_code);
cond_local_irq_disable(regs);
debug_stack_usage_dec();
+}
+
+static __always_inline void exc_debug_kernel(struct pt_regs *regs,
+ unsigned long dr6)
+{
+ nmi_enter();
+ handle_debug(regs, dr6);
+ nmi_exit();
+}
+
+static __always_inline void exc_debug_user(struct pt_regs *regs,
+ unsigned long dr6)
+{
+ idtentry_enter(regs);
+ handle_debug(regs, dr6);
+ idtentry_exit(regs);
+}
+
+#ifdef CONFIG_X86_64
+/* IST stack entry */
+DEFINE_IDTENTRY_DEBUG(exc_debug)
+{
+ unsigned long dr6, dr7;
+
+ debug_enter(&dr6, &dr7);
+ exc_debug_kernel(regs, dr6);
+ debug_exit(dr7);
+}
+
+/* User entry, runs on regular task stack */
+DEFINE_IDTENTRY_DEBUG_USER(exc_debug)
+{
+ unsigned long dr6, dr7;
+
+ debug_enter(&dr6, &dr7);
+ exc_debug_user(regs, dr6);
+ debug_exit(dr7);
+}
+#else
+/* 32 bit does not have separate entry points. */
+DEFINE_IDTENTRY_DEBUG(exc_debug)
+{
+ unsigned long dr6, dr7;
+
+ debug_enter(&dr6, &dr7);
-exit:
if (user_mode(regs))
- idtentry_exit(regs);
+ exc_debug_user(regs, dr6);
else
- nmi_exit();
+ exc_debug_kernel(regs, dr6);
+
debug_exit(dr7);
}
+#endif
/*
* Note that we play around with the 'TS' bit in an attempt to get
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