From 593309423cbad0fab659a685834416cf12d8f581 Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Sat, 4 Apr 2020 01:33:05 +0200 Subject: [PATCH] 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 Acked-by: Andy Lutomirski Link: https://lkml.kernel.org/r/20200404083646.8897-1-bp@alien8.de --- arch/x86/Kconfig.debug | 9 --------- arch/x86/entry/entry_32.S | 2 -- arch/x86/include/asm/doublefault.h | 2 +- arch/x86/include/asm/traps.h | 2 -- arch/x86/kernel/Makefile | 4 +--- arch/x86/kernel/dumpstack_32.c | 4 ---- arch/x86/kernel/traps.c | 2 -- arch/x86/mm/cpu_entry_area.c | 4 +--- tools/testing/selftests/wireguard/qemu/debug.config | 1 - 9 files changed, 3 insertions(+), 27 deletions(-) diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug index 2e74690..f909d3c 100644 --- a/arch/x86/Kconfig.debug +++ b/arch/x86/Kconfig.debug @@ -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 diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index b67bae7..5c9c7ee 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -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 diff --git a/arch/x86/include/asm/doublefault.h b/arch/x86/include/asm/doublefault.h index af9a14a..54a6e4a 100644 --- a/arch/x86/include/asm/doublefault.h +++ b/arch/x86/include/asm/doublefault.h @@ -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) diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h index c26a7e1..70bd0f3 100644 --- a/arch/x86/include/asm/traps.h +++ b/arch/x86/include/asm/traps.h @@ -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); diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index ba89cab..2a7c3af 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -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 diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c index 8e3a8fed..722fd712 100644 --- a/arch/x86/kernel/dumpstack_32.c +++ b/arch/x86/kernel/dumpstack_32.c @@ -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 } diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index d54cffd..e85561f 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -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) { diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c index 56f9189..5199d8a 100644 --- a/arch/x86/mm/cpu_entry_area.c +++ b/arch/x86/mm/cpu_entry_area.c @@ -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 diff --git a/tools/testing/selftests/wireguard/qemu/debug.config b/tools/testing/selftests/wireguard/qemu/debug.config index 5909e7e..807fa7d 100644 --- a/tools/testing/selftests/wireguard/qemu/debug.config +++ b/tools/testing/selftests/wireguard/qemu/debug.config @@ -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 -- 2.7.4