Commit 6f442be2 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Linus Torvalds

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
...@@ -20,7 +20,6 @@ ...@@ -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
......
...@@ -14,12 +14,11 @@ ...@@ -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))
......
...@@ -39,6 +39,7 @@ asmlinkage void simd_coprocessor_error(void); ...@@ -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
......
...@@ -24,7 +24,6 @@ static char x86_stack_ids[][8] = { ...@@ -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 ...
......
...@@ -1259,7 +1259,7 @@ apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \ ...@@ -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
......
...@@ -233,27 +233,11 @@ DO_ERROR(X86_TRAP_UD, SIGILL, "invalid opcode", invalid_op) ...@@ -233,27 +233,11 @@ DO_ERROR(X86_TRAP_UD, SIGILL, "invalid opcode", invalid_op)
DO_ERROR(X86_TRAP_OLD_MF, SIGFPE, "coprocessor segment overrun",coprocessor_segment_overrun) DO_ERROR(X86_TRAP_OLD_MF, SIGFPE, "coprocessor segment overrun",coprocessor_segment_overrun)
DO_ERROR(X86_TRAP_TS, SIGSEGV, "invalid TSS", invalid_TSS) DO_ERROR(X86_TRAP_TS, SIGSEGV, "invalid TSS", invalid_TSS)
DO_ERROR(X86_TRAP_NP, SIGBUS, "segment not present", segment_not_present) DO_ERROR(X86_TRAP_NP, SIGBUS, "segment not present", segment_not_present)
#ifdef CONFIG_X86_32
DO_ERROR(X86_TRAP_SS, SIGBUS, "stack segment", stack_segment) DO_ERROR(X86_TRAP_SS, SIGBUS, "stack segment", stack_segment)
#endif
DO_ERROR(X86_TRAP_AC, SIGBUS, "alignment check", alignment_check) DO_ERROR(X86_TRAP_AC, SIGBUS, "alignment check", alignment_check)
#ifdef CONFIG_X86_64 #ifdef CONFIG_X86_64
/* Runs on IST stack */ /* Runs on IST stack */
dotraplinkage void do_stack_segment(struct pt_regs *regs, long error_code)
{
enum ctx_state prev_state;
prev_state = exception_enter();
if (notify_die(DIE_TRAP, "stack segment", regs, error_code,
X86_TRAP_SS, SIGBUS) != NOTIFY_STOP) {
preempt_conditional_sti(regs);
do_trap(X86_TRAP_SS, SIGBUS, "stack segment", regs, error_code, NULL);
preempt_conditional_cli(regs);
}
exception_exit(prev_state);
}
dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code) dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code)
{ {
static const char str[] = "double fault"; static const char str[] = "double fault";
...@@ -802,7 +786,7 @@ void __init trap_init(void) ...@@ -802,7 +786,7 @@ void __init trap_init(void)
set_intr_gate(X86_TRAP_OLD_MF, coprocessor_segment_overrun); set_intr_gate(X86_TRAP_OLD_MF, coprocessor_segment_overrun);
set_intr_gate(X86_TRAP_TS, invalid_TSS); set_intr_gate(X86_TRAP_TS, invalid_TSS);
set_intr_gate(X86_TRAP_NP, segment_not_present); set_intr_gate(X86_TRAP_NP, segment_not_present);
set_intr_gate_ist(X86_TRAP_SS, &stack_segment, STACKFAULT_STACK); set_intr_gate(X86_TRAP_SS, stack_segment);
set_intr_gate(X86_TRAP_GP, general_protection); set_intr_gate(X86_TRAP_GP, general_protection);
set_intr_gate(X86_TRAP_SPURIOUS, spurious_interrupt_bug); set_intr_gate(X86_TRAP_SPURIOUS, spurious_interrupt_bug);
set_intr_gate(X86_TRAP_MF, coprocessor_error); set_intr_gate(X86_TRAP_MF, coprocessor_error);
......
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