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x86/32: Remove CONFIG_DOUBLEFAULT 

Make the doublefault exception handler unconditional on 32-bit. Yes,
it is important to be able to catch #DF exceptions instead of silent
reboots. Yes, the code size increase is worth every byte. And one less
CONFIG symbol is just the cherry on top.

No functional changes.

Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200404083646.8897-1-bp@alien8.de
This commit is contained in:
Borislav Petkov 2020-04-04 01:33:05 +02:00
parent 8f3d9f3542
commit 593309423c
9 changed files with 3 additions and 27 deletions
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9
arch/x86/Kconfig.debug
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@ -99,15 +99,6 @@ config DEBUG_WX
If in doubt, say "Y".
config DOUBLEFAULT
default y
bool "Enable doublefault exception handler" if EXPERT && X86_32
---help---
This option allows trapping of rare doublefault exceptions that
would otherwise cause a system to silently reboot. Disabling this
option saves about 4k and might cause you much additional grey
hair.
config DEBUG_TLBFLUSH
bool "Set upper limit of TLB entries to flush one-by-one"
depends on DEBUG_KERNEL

2
arch/x86/entry/entry_32.S
View File

@ -1536,7 +1536,6 @@ SYM_CODE_START(debug)
jmp common_exception
SYM_CODE_END(debug)
#ifdef CONFIG_DOUBLEFAULT
SYM_CODE_START(double_fault)
1:
/*
@ -1576,7 +1575,6 @@ SYM_CODE_START(double_fault)
hlt
jmp 1b
SYM_CODE_END(double_fault)
#endif
/*
* NMI is doubly nasty. It can happen on the first instruction of

2
arch/x86/include/asm/doublefault.h
View File

@ -2,7 +2,7 @@
#ifndef _ASM_X86_DOUBLEFAULT_H
#define _ASM_X86_DOUBLEFAULT_H
#if defined(CONFIG_X86_32) && defined(CONFIG_DOUBLEFAULT)
#ifdef CONFIG_X86_32
extern void doublefault_init_cpu_tss(void);
#else
static inline void doublefault_init_cpu_tss(void)

2
arch/x86/include/asm/traps.h
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@ -69,9 +69,7 @@ dotraplinkage void do_overflow(struct pt_regs *regs, long error_code);
dotraplinkage void do_bounds(struct pt_regs *regs, long error_code);
dotraplinkage void do_invalid_op(struct pt_regs *regs, long error_code);
dotraplinkage void do_device_not_available(struct pt_regs *regs, long error_code);
#if defined(CONFIG_X86_64) || defined(CONFIG_DOUBLEFAULT)
dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code, unsigned long cr2);
#endif
dotraplinkage void do_coprocessor_segment_overrun(struct pt_regs *regs, long error_code);
dotraplinkage void do_invalid_TSS(struct pt_regs *regs, long error_code);
dotraplinkage void do_segment_not_present(struct pt_regs *regs, long error_code);

4
arch/x86/kernel/Makefile
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@ -102,9 +102,7 @@ obj-$(CONFIG_KEXEC_FILE) += kexec-bzimage64.o
obj-$(CONFIG_CRASH_DUMP) += crash_dump_$(BITS).o
obj-y += kprobes/
obj-$(CONFIG_MODULES) += module.o
ifeq ($(CONFIG_X86_32),y)
obj-$(CONFIG_DOUBLEFAULT) += doublefault_32.o
endif
obj-$(CONFIG_X86_32) += doublefault_32.o
obj-$(CONFIG_KGDB) += kgdb.o
obj-$(CONFIG_VM86) += vm86_32.o
obj-$(CONFIG_EARLY_PRINTK) += early_printk.o

4
arch/x86/kernel/dumpstack_32.c
View File

@ -87,7 +87,6 @@ static bool in_softirq_stack(unsigned long *stack, struct stack_info *info)
static bool in_doublefault_stack(unsigned long *stack, struct stack_info *info)
{
#ifdef CONFIG_DOUBLEFAULT
struct cpu_entry_area *cea = get_cpu_entry_area(raw_smp_processor_id());
struct doublefault_stack *ss = &cea->doublefault_stack;
@ -103,9 +102,6 @@ static bool in_doublefault_stack(unsigned long *stack, struct stack_info *info)
info->next_sp = (unsigned long *)this_cpu_read(cpu_tss_rw.x86_tss.sp);
return true;
#else
return false;
#endif
}

2
arch/x86/kernel/traps.c
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@ -326,7 +326,6 @@ __visible void __noreturn handle_stack_overflow(const char *message,
}
#endif
#if defined(CONFIG_X86_64) || defined(CONFIG_DOUBLEFAULT)
/*
* Runs on an IST stack for x86_64 and on a special task stack for x86_32.
*
@ -450,7 +449,6 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code, unsign
die("double fault", regs, error_code);
panic("Machine halted.");
}
#endif
dotraplinkage void do_bounds(struct pt_regs *regs, long error_code)
{

4
arch/x86/mm/cpu_entry_area.c
View File

@ -17,7 +17,7 @@ static DEFINE_PER_CPU_PAGE_ALIGNED(struct exception_stacks, exception_stacks);
DEFINE_PER_CPU(struct cea_exception_stacks*, cea_exception_stacks);
#endif
#if defined(CONFIG_X86_32) && defined(CONFIG_DOUBLEFAULT)
#ifdef CONFIG_X86_32
DECLARE_PER_CPU_PAGE_ALIGNED(struct doublefault_stack, doublefault_stack);
#endif
@ -114,12 +114,10 @@ static void __init percpu_setup_exception_stacks(unsigned int cpu)
#else
static inline void percpu_setup_exception_stacks(unsigned int cpu)
{
#ifdef CONFIG_DOUBLEFAULT
struct cpu_entry_area *cea = get_cpu_entry_area(cpu);
cea_map_percpu_pages(&cea->doublefault_stack,
&per_cpu(doublefault_stack, cpu), 1, PAGE_KERNEL);
#endif
}
#endif

1
tools/testing/selftests/wireguard/qemu/debug.config
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@ -58,7 +58,6 @@ CONFIG_RCU_EQS_DEBUG=y
CONFIG_USER_STACKTRACE_SUPPORT=y
CONFIG_DEBUG_SG=y
CONFIG_DEBUG_NOTIFIERS=y
CONFIG_DOUBLEFAULT=y
CONFIG_X86_DEBUG_FPU=y
CONFIG_DEBUG_SECTION_MISMATCH=y
CONFIG_DEBUG_PAGEALLOC=y