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x86/entry: Implement user mode C entry points for #DB and #MCE

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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@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505135315.177564104@linutronix.de
This commit is contained in:
Thomas Gleixner 2020-02-25 23:33:29 +01:00
parent f08e32ec3c
commit 4c0dcd8350
3 changed files with 94 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/entry/entry_64.S
View File

@ -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)

48
arch/x86/kernel/cpu/mce/core.c
View File

@ -1904,25 +1904,51 @@ 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);
if (user_mode(regs))
idtentry_exit(regs);
else
nmi_exit();
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))
exc_machine_check_user(regs);
else
exc_machine_check_kernel(regs);
}
#endif
/*
* Called for each booted CPU to set up machine checks.
* Must be called with preempt off:

74
arch/x86/kernel/traps.c
View File

@ -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))) {
@ -861,15 +853,61 @@ DEFINE_IDTENTRY_DEBUG(exc_debug)
send_sigtrap(regs, 0, si_code);
cond_local_irq_disable(regs);
debug_stack_usage_dec();
}
exit:
if (user_mode(regs))
idtentry_exit(regs);
else
nmi_exit();
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);
if (user_mode(regs))
exc_debug_user(regs, dr6);
else
exc_debug_kernel(regs, dr6);
debug_exit(dr7);
}
#endif
/*
* Note that we play around with the 'TS' bit in an attempt to get
* the correct behaviour even in the presence of the asynchronous