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Message-Id: <20200404083646.8897-1-bp@alien8.de>
Date: Sat, 4 Apr 2020 10:36:46 +0200
From: Borislav Petkov <bp@...en8.de>
To: X86 ML <x86@...nel.org>
Cc: LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86/32: Remove CONFIG_DOUBLEFAULT
From: Borislav Petkov <bp@...e.de>
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@...e.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 2e74690b028a..f909d3ce36e6 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 b67bae7091d7..5c9c7eee6325 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 af9a14ac8962..54a6e4a2e132 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 c26a7e1d8a2c..70bd0f356e5d 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 3c131adb2ca9..fd497883562f 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -106,9 +106,7 @@ 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 8e3a8fedfa4d..722fd712e1cf 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 d54cffdc7cac..e85561fc0dc8 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 56f9189bbadb..5199d8a1daf1 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 5909e7ef2a5c..807fa7dc60b8 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
--
2.21.0
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