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x86/entry: Remove DBn stacks

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Both #DB itself, as all other IST users (NMI, #MC) now clear DR7 on
entry. Combined with not allowing breakpoints on entry/noinstr/NOKPROBE
text and no single step (EFLAGS.TF) inside the #DB handler should guarantee
no nested #DB.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200529213321.303027161@infradead.org
This commit is contained in:
Peter Zijlstra
2020-05-29 23:27:38 +02:00
committed by Thomas Gleixner
parent f9912ada82
commit fd501d4f03
5 changed files with 5 additions and 35 deletions
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7
arch/x86/kernel/dumpstack_64.c
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@@ -22,15 +22,13 @@
static const char * const exception_stack_names[] = {
[ ESTACK_DF ] = "#DF",
[ ESTACK_NMI ] = "NMI",
[ ESTACK_DB2 ] = "#DB2",
[ ESTACK_DB1 ] = "#DB1",
[ ESTACK_DB ] = "#DB",
[ ESTACK_MCE ] = "#MC",
};
const char *stack_type_name(enum stack_type type)
{
BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);
BUILD_BUG_ON(N_EXCEPTION_STACKS != 4);
if (type == STACK_TYPE_IRQ)
return "IRQ";
@@ -79,7 +77,6 @@ static const
struct estack_pages estack_pages[CEA_ESTACK_PAGES] ____cacheline_aligned = {
EPAGERANGE(DF),
EPAGERANGE(NMI),
EPAGERANGE(DB1),
EPAGERANGE(DB),
EPAGERANGE(MCE),
};
@@ -91,7 +88,7 @@ static bool in_exception_stack(unsigned long *stack, struct stack_info *info)
struct pt_regs *regs;
unsigned int k;
BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);
BUILD_BUG_ON(N_EXCEPTION_STACKS != 4);
begin = (unsigned long)__this_cpu_read(cea_exception_stacks);
/*