147 lines
5.6 KiB
Diff
147 lines
5.6 KiB
Diff
From f4c2632940c4e767d622c109f9cbcb046d432961 Mon Sep 17 00:00:00 2001
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From: Andy Lutomirski <luto@amacapital.net>
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Date: Sat, 22 Nov 2014 18:00:32 -0800
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Subject: [PATCH] x86_64, traps: Stop using IST for #SS
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On a 32-bit kernel, this has no effect, since there are no IST stacks.
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On a 64-bit kernel, #SS can only happen in user code, on a failed iret
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to user space, a canonical violation on access via RSP or RBP, or a
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genuine stack segment violation in 32-bit kernel code. The first two
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cases don't need IST, and the latter two cases are unlikely fatal bugs,
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and promoting them to double faults would be fine.
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This fixes a bug in which the espfix64 code mishandles a stack segment
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violation.
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This saves 4k of memory per CPU and a tiny bit of code.
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Signed-off-by: Andy Lutomirski <luto@amacapital.net>
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Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
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Cc: stable@vger.kernel.org
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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arch/x86/include/asm/page_32_types.h | 1 -
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arch/x86/include/asm/page_64_types.h | 11 +++++------
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arch/x86/include/asm/traps.h | 1 +
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arch/x86/kernel/dumpstack_64.c | 1 -
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arch/x86/kernel/entry_64.S | 2 +-
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arch/x86/kernel/traps.c | 18 +-----------------
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6 files changed, 8 insertions(+), 26 deletions(-)
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diff --git a/arch/x86/include/asm/page_32_types.h b/arch/x86/include/asm/page_32_types.h
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index f48b17df4224..3a52ee0e726d 100644
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--- a/arch/x86/include/asm/page_32_types.h
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+++ b/arch/x86/include/asm/page_32_types.h
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@@ -20,7 +20,6 @@
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#define THREAD_SIZE_ORDER 1
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#define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER)
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-#define STACKFAULT_STACK 0
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#define DOUBLEFAULT_STACK 1
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#define NMI_STACK 0
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#define DEBUG_STACK 0
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diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
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index 8de6d9cf3b95..d54d1eebeffe 100644
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--- a/arch/x86/include/asm/page_64_types.h
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+++ b/arch/x86/include/asm/page_64_types.h
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@@ -14,12 +14,11 @@
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#define IRQ_STACK_ORDER 2
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#define IRQ_STACK_SIZE (PAGE_SIZE << IRQ_STACK_ORDER)
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-#define STACKFAULT_STACK 1
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-#define DOUBLEFAULT_STACK 2
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-#define NMI_STACK 3
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-#define DEBUG_STACK 4
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-#define MCE_STACK 5
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-#define N_EXCEPTION_STACKS 5 /* hw limit: 7 */
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+#define DOUBLEFAULT_STACK 1
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+#define NMI_STACK 2
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+#define DEBUG_STACK 3
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+#define MCE_STACK 4
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+#define N_EXCEPTION_STACKS 4 /* hw limit: 7 */
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#define PUD_PAGE_SIZE (_AC(1, UL) << PUD_SHIFT)
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#define PUD_PAGE_MASK (~(PUD_PAGE_SIZE-1))
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diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
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index 58d66fe06b61..b409b17efb48 100644
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--- a/arch/x86/include/asm/traps.h
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+++ b/arch/x86/include/asm/traps.h
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@@ -39,6 +39,7 @@ asmlinkage void simd_coprocessor_error(void);
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#ifdef CONFIG_TRACING
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asmlinkage void trace_page_fault(void);
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+#define trace_stack_segment stack_segment
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#define trace_divide_error divide_error
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#define trace_bounds bounds
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#define trace_invalid_op invalid_op
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diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
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index addb207dab92..66e274a3d968 100644
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--- a/arch/x86/kernel/dumpstack_64.c
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+++ b/arch/x86/kernel/dumpstack_64.c
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@@ -24,7 +24,6 @@ static char x86_stack_ids[][8] = {
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[ DEBUG_STACK-1 ] = "#DB",
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[ NMI_STACK-1 ] = "NMI",
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[ DOUBLEFAULT_STACK-1 ] = "#DF",
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- [ STACKFAULT_STACK-1 ] = "#SS",
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[ MCE_STACK-1 ] = "#MC",
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#if DEBUG_STKSZ > EXCEPTION_STKSZ
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[ N_EXCEPTION_STACKS ...
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diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
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index 03cd2a8f6009..d41418880506 100644
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--- a/arch/x86/kernel/entry_64.S
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+++ b/arch/x86/kernel/entry_64.S
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@@ -1549,7 +1549,7 @@ apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \
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paranoidzeroentry_ist debug do_debug DEBUG_STACK
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paranoidzeroentry_ist int3 do_int3 DEBUG_STACK
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-paranoiderrorentry stack_segment do_stack_segment
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+errorentry stack_segment do_stack_segment
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#ifdef CONFIG_XEN
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zeroentry xen_debug do_debug
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zeroentry xen_int3 do_int3
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diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
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index 57409f6b8c62..f208d879a81a 100644
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--- a/arch/x86/kernel/traps.c
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+++ b/arch/x86/kernel/traps.c
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@@ -218,27 +218,11 @@ DO_ERROR_INFO(X86_TRAP_UD, SIGILL, "invalid opcode", invalid_op, ILL
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DO_ERROR (X86_TRAP_OLD_MF, SIGFPE, "coprocessor segment overrun", coprocessor_segment_overrun )
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DO_ERROR (X86_TRAP_TS, SIGSEGV, "invalid TSS", invalid_TSS )
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DO_ERROR (X86_TRAP_NP, SIGBUS, "segment not present", segment_not_present )
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-#ifdef CONFIG_X86_32
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DO_ERROR (X86_TRAP_SS, SIGBUS, "stack segment", stack_segment )
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-#endif
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DO_ERROR_INFO(X86_TRAP_AC, SIGBUS, "alignment check", alignment_check, BUS_ADRALN, 0 )
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#ifdef CONFIG_X86_64
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/* Runs on IST stack */
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-dotraplinkage void do_stack_segment(struct pt_regs *regs, long error_code)
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-{
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- enum ctx_state prev_state;
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-
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- prev_state = exception_enter();
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- if (notify_die(DIE_TRAP, "stack segment", regs, error_code,
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- X86_TRAP_SS, SIGBUS) != NOTIFY_STOP) {
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- preempt_conditional_sti(regs);
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- do_trap(X86_TRAP_SS, SIGBUS, "stack segment", regs, error_code, NULL);
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- preempt_conditional_cli(regs);
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- }
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- exception_exit(prev_state);
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-}
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-
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dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code)
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{
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static const char str[] = "double fault";
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@@ -748,7 +732,7 @@ void __init trap_init(void)
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set_intr_gate(X86_TRAP_OLD_MF, coprocessor_segment_overrun);
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set_intr_gate(X86_TRAP_TS, invalid_TSS);
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set_intr_gate(X86_TRAP_NP, segment_not_present);
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- set_intr_gate_ist(X86_TRAP_SS, &stack_segment, STACKFAULT_STACK);
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+ set_intr_gate(X86_TRAP_SS, stack_segment);
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set_intr_gate(X86_TRAP_GP, general_protection);
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set_intr_gate(X86_TRAP_SPURIOUS, spurious_interrupt_bug);
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set_intr_gate(X86_TRAP_MF, coprocessor_error);
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--
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1.9.3
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