[tip: x86/entry] x86/entry: Implement user mode C entry points for #DB and #MCE
From: tip-bot2 for Thomas Gleixner
Date: Tue May 19 2020 - 16:02:17 EST
The following commit has been merged into the x86/entry branch of tip:
Commit-ID: 210d5380b6e055f0cd991a2ebefaa884689d4f95
Gitweb: https://git.kernel.org/tip/210d5380b6e055f0cd991a2ebefaa884689d4f95
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Tue, 25 Feb 2020 23:33:29 +01:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Tue, 19 May 2020 16:04:12 +02:00
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 nmi_enter/exit()
magic in the IST variant. Fixup the ASM code to emit the proper
noist_##cfunc call.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Acked-by: Andy Lutomirski <luto@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200505135315.177564104@xxxxxxxxxxxxx
---
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(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index eeb4285..d302839 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -657,7 +657,7 @@ 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)
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 3177652..a72c013 100644
--- 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(struct pt_regs *regs)
/* 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.
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 569408a..4f248c5 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -775,20 +775,12 @@ static __always_inline void debug_exit(unsigned long dr7)
*
* 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
@@ -800,7 +792,7 @@ 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
@@ -821,12 +813,12 @@ 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
@@ -842,7 +834,7 @@ 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))) {
@@ -861,14 +853,60 @@ 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