[RFC PATCH] x86: Remove CONFIG_DOUBLEFAULT
From: Borislav Petkov
Date: Wed Nov 27 2019 - 14:39:53 EST
On Wed, Nov 27, 2019 at 08:19:29AM -0000, tip-bot2 for Andy Lutomirski wrote:
> The following commit has been merged into the x86/urgent branch of tip:
>
> Commit-ID: 93efbde2c331004d8053f04b4bf0ca3e630b474a
> Gitweb: https://git.kernel.org/tip/93efbde2c331004d8053f04b4bf0ca3e630b474a
> Author: Andy Lutomirski <luto@xxxxxxxxxx>
> AuthorDate: Wed, 20 Nov 2019 22:12:38 -08:00
> Committer: Ingo Molnar <mingo@xxxxxxxxxx>
> CommitterDate: Tue, 26 Nov 2019 21:53:34 +01:00
>
> x86/traps: Disentangle the 32-bit and 64-bit doublefault code
>
> The 64-bit doublefault handler is much nicer than the 32-bit one.
> As a first step toward unifying them, make the 64-bit handler
> self-contained. This should have no effect no functional effect
> except in the odd case of x86_64 with CONFIG_DOUBLEFAULT=n in which
> case it will change the logging a bit.
>
> This also gets rid of CONFIG_DOUBLEFAULT configurability on 64-bit
> kernels. It didn't do anything useful -- CONFIG_DOUBLEFAULT=n
> didn't actually disable doublefault handling on x86_64.
>
> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> ---
> arch/x86/Kconfig.debug | 2 +-
> arch/x86/include/asm/processor.h | 1 -
> arch/x86/kernel/doublefault.c | 11 -----------
> arch/x86/kernel/traps.c | 12 +++---------
> 4 files changed, 4 insertions(+), 22 deletions(-)
>
> diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
> index 409c00f..c4eab8e 100644
> --- a/arch/x86/Kconfig.debug
> +++ b/arch/x86/Kconfig.debug
> @@ -117,7 +117,7 @@ config DEBUG_WX
>
> config DOUBLEFAULT
> default y
> - bool "Enable doublefault exception handler" if EXPERT
> + bool "Enable doublefault exception handler" if EXPERT && X86_32
Yeah, how about we simplify the whole df code even more. It is clearly
much better to always have a registered #DF handler so let's get rid of
that silly config option.
Only compile-tested.
---
From: Borislav Petkov <bp@xxxxxxx>
Date: Wed, 27 Nov 2019 19:12:29 +0100
Subject: [RFC PATCH] x86: Remove CONFIG_DOUBLEFAULT
... and make it unconditional.
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
---
arch/x86/Kconfig.debug | 9 ---------
arch/x86/entry/entry_32.S | 2 --
arch/x86/include/asm/doublefault.h | 6 ++----
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 +---
8 files changed, 4 insertions(+), 29 deletions(-)
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index c4eab8ed33a3..f386068114d6 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -115,15 +115,6 @@ 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 7e0560442538..8bd285617c21 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..65b58363797e 100644
--- a/arch/x86/include/asm/doublefault.h
+++ b/arch/x86/include/asm/doublefault.h
@@ -2,12 +2,10 @@
#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)
-{
-}
+static inline void doublefault_init_cpu_tss(void) { }
#endif
#endif /* _ASM_X86_DOUBLEFAULT_H */
diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index ffa0dc8a535e..4580c8207da3 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 ccb13271895d..0f5bdf6dfce6 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -104,9 +104,7 @@ 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 f19de6f45d48..3bcbf5c3d1f0 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -306,7 +306,6 @@ __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.
*
@@ -430,7 +429,6 @@ 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
--
2.21.0
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette