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Commit 6f442be2 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Linus Torvalds
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x86_64, traps: Stop using IST for #SS 



On a 32-bit kernel, this has no effect, since there are no IST stacks.

On a 64-bit kernel, #SS can only happen in user code, on a failed iret
to user space, a canonical violation on access via RSP or RBP, or a
genuine stack segment violation in 32-bit kernel code.  The first two
cases don't need IST, and the latter two cases are unlikely fatal bugs,
and promoting them to double faults would be fine.

This fixes a bug in which the espfix64 code mishandles a stack segment
violation.

This saves 4k of memory per CPU and a tiny bit of code.

Signed-off-by: default avatarAndy Lutomirski <luto@amacapital.net>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent af726f21

arch/x86/include/asm/page_32_types.h

+0 −1
Original line number Original line Diff line number Diff line
@@ -20,7 +20,6 @@ 
#define THREAD_SIZE_ORDER	1

#define THREAD_SIZE_ORDER	1

#define THREAD_SIZE		(PAGE_SIZE << THREAD_SIZE_ORDER)

#define THREAD_SIZE		(PAGE_SIZE << THREAD_SIZE_ORDER)





#define STACKFAULT_STACK 0

#define DOUBLEFAULT_STACK 1

#define DOUBLEFAULT_STACK 1

#define NMI_STACK 0

#define NMI_STACK 0

#define DEBUG_STACK 0

#define DEBUG_STACK 0

arch/x86/include/asm/page_64_types.h

+5 −6
Original line number Original line Diff line number Diff line
@@ -14,12 +14,11 @@ 
#define IRQ_STACK_ORDER 2

#define IRQ_STACK_ORDER 2

#define IRQ_STACK_SIZE (PAGE_SIZE << IRQ_STACK_ORDER)

#define IRQ_STACK_SIZE (PAGE_SIZE << IRQ_STACK_ORDER)





#define STACKFAULT_STACK 1

#define DOUBLEFAULT_STACK 1

#define DOUBLEFAULT_STACK 2

#define NMI_STACK 2

#define NMI_STACK 3

#define DEBUG_STACK 3

#define DEBUG_STACK 4

#define MCE_STACK 4

#define MCE_STACK 5

#define N_EXCEPTION_STACKS 4  /* hw limit: 7 */

#define N_EXCEPTION_STACKS 5  /* hw limit: 7 */





#define PUD_PAGE_SIZE		(_AC(1, UL) << PUD_SHIFT)

#define PUD_PAGE_SIZE		(_AC(1, UL) << PUD_SHIFT)

#define PUD_PAGE_MASK		(~(PUD_PAGE_SIZE-1))

#define PUD_PAGE_MASK		(~(PUD_PAGE_SIZE-1))

arch/x86/include/asm/traps.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -39,6 +39,7 @@ asmlinkage void simd_coprocessor_error(void); 




#ifdef CONFIG_TRACING

#ifdef CONFIG_TRACING

asmlinkage void trace_page_fault(void);

asmlinkage void trace_page_fault(void);

#define trace_stack_segment stack_segment

#define trace_divide_error divide_error

#define trace_divide_error divide_error

#define trace_bounds bounds

#define trace_bounds bounds

#define trace_invalid_op invalid_op

#define trace_invalid_op invalid_op

arch/x86/kernel/dumpstack_64.c

+0 −1
Original line number Original line Diff line number Diff line
@@ -24,7 +24,6 @@ static char x86_stack_ids[][8] = { 
		[ DEBUG_STACK-1			]	= "#DB",

		[ DEBUG_STACK-1			]	= "#DB",

		[ NMI_STACK-1			]	= "NMI",

		[ NMI_STACK-1			]	= "NMI",

		[ DOUBLEFAULT_STACK-1		]	= "#DF",

		[ DOUBLEFAULT_STACK-1		]	= "#DF",

		[ STACKFAULT_STACK-1		]	= "#SS",

		[ MCE_STACK-1			]	= "#MC",

		[ MCE_STACK-1			]	= "#MC",

#if DEBUG_STKSZ > EXCEPTION_STKSZ

#if DEBUG_STKSZ > EXCEPTION_STKSZ

		[ N_EXCEPTION_STACKS ...

		[ N_EXCEPTION_STACKS ...

arch/x86/kernel/entry_64.S

+1 −1
Original line number Original line Diff line number Diff line
@@ -1259,7 +1259,7 @@ apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \ 




idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK

idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK

idtentry int3 do_int3 has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK

idtentry int3 do_int3 has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK

idtentry stack_segment do_stack_segment has_error_code=1 paranoid=1

idtentry stack_segment do_stack_segment has_error_code=1

#ifdef CONFIG_XEN

#ifdef CONFIG_XEN

idtentry xen_debug do_debug has_error_code=0

idtentry xen_debug do_debug has_error_code=0

idtentry xen_int3 do_int3 has_error_code=0

idtentry xen_int3 do_int3 has_error_code=0