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* [PATCH] x86/32: Remove CONFIG_DOUBLEFAULT
@ 2020-04-04  8:36 Borislav Petkov
  2020-04-04 21:13 ` Andy Lutomirski
  2020-04-14 12:41 ` [tip: x86/asm] " tip-bot2 for Borislav Petkov
  0 siblings, 2 replies; 3+ messages in thread
From: Borislav Petkov @ 2020-04-04  8:36 UTC (permalink / raw)
  To: X86 ML; +Cc: LKML

From: Borislav Petkov <bp@suse.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@suse.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


^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [PATCH] x86/32: Remove CONFIG_DOUBLEFAULT
  2020-04-04  8:36 [PATCH] x86/32: Remove CONFIG_DOUBLEFAULT Borislav Petkov
@ 2020-04-04 21:13 ` Andy Lutomirski
  2020-04-14 12:41 ` [tip: x86/asm] " tip-bot2 for Borislav Petkov
  1 sibling, 0 replies; 3+ messages in thread
From: Andy Lutomirski @ 2020-04-04 21:13 UTC (permalink / raw)
  To: Borislav Petkov; +Cc: X86 ML, LKML

On Sat, Apr 4, 2020 at 1:36 AM Borislav Petkov <bp@alien8.de> wrote:
>
> From: Borislav Petkov <bp@suse.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.
>

Acked-by: Andy Lutomirski <luto@kernel.org>

^ permalink raw reply	[flat|nested] 3+ messages in thread
* [tip: x86/asm] x86/32: Remove CONFIG_DOUBLEFAULT
  2020-04-04  8:36 [PATCH] x86/32: Remove CONFIG_DOUBLEFAULT Borislav Petkov
  2020-04-04 21:13 ` Andy Lutomirski
@ 2020-04-14 12:41 ` tip-bot2 for Borislav Petkov
  1 sibling, 0 replies; 3+ messages in thread
From: tip-bot2 for Borislav Petkov @ 2020-04-14 12:41 UTC (permalink / raw)
  To: linux-tip-commits; +Cc: Borislav Petkov, Andy Lutomirski, x86, LKML

The following commit has been merged into the x86/asm branch of tip:

Commit-ID:     593309423cbad0fab659a685834416cf12d8f581
Gitweb:        https://git.kernel.org/tip/593309423cbad0fab659a685834416cf12d8f581
Author:        Borislav Petkov <bp@suse.de>
AuthorDate:    Sat, 04 Apr 2020 01:33:05 +02:00
Committer:     Borislav Petkov <bp@suse.de>
CommitterDate: Tue, 14 Apr 2020 14:24:05 +02:00

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
---
 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 8e3a8fe..722fd71 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

^ permalink raw reply related	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-04-14 12:41 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2020-04-04  8:36 [PATCH] x86/32: Remove CONFIG_DOUBLEFAULT Borislav Petkov
2020-04-04 21:13 ` Andy Lutomirski
2020-04-14 12:41 ` [tip: x86/asm] " tip-bot2 for Borislav Petkov

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