Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752864AbaLFPTo (ORCPT ); Sat, 6 Dec 2014 10:19:44 -0500 Received: from ip4-83-240-67-251.cust.nbox.cz ([83.240.67.251]:47674 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752213AbaLFPIK (ORCPT ); Sat, 6 Dec 2014 10:08:10 -0500 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andy Lutomirski , Linus Torvalds , Jiri Slaby Subject: [PATCH 3.12 14/66] x86_64, traps: Stop using IST for #SS Date: Sat, 6 Dec 2014 16:07:06 +0100 Message-Id: X-Mailer: git-send-email 2.1.3 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andy Lutomirski 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 6f442be2fb22be02cafa606f1769fa1e6f894441 upstream. 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: Andy Lutomirski Reviewed-by: Thomas Gleixner Signed-off-by: Linus Torvalds Signed-off-by: Jiri Slaby --- arch/x86/include/asm/page_32_types.h | 1 - arch/x86/include/asm/page_64_types.h | 11 +++++------ arch/x86/kernel/dumpstack_64.c | 1 - arch/x86/kernel/entry_64.S | 2 +- arch/x86/kernel/traps.c | 18 +----------------- 5 files changed, 7 insertions(+), 26 deletions(-) diff --git a/arch/x86/include/asm/page_32_types.h b/arch/x86/include/asm/page_32_types.h index f48b17df4224..3a52ee0e726d 100644 --- a/arch/x86/include/asm/page_32_types.h +++ b/arch/x86/include/asm/page_32_types.h @@ -20,7 +20,6 @@ #define THREAD_SIZE_ORDER 1 #define THREAD_SIZE (PAGE_SIZE << THREAD_SIZE_ORDER) -#define STACKFAULT_STACK 0 #define DOUBLEFAULT_STACK 1 #define NMI_STACK 0 #define DEBUG_STACK 0 diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h index 43dcd804ebd5..d1d2972a54db 100644 --- a/arch/x86/include/asm/page_64_types.h +++ b/arch/x86/include/asm/page_64_types.h @@ -14,12 +14,11 @@ #define IRQ_STACK_ORDER 2 #define IRQ_STACK_SIZE (PAGE_SIZE << IRQ_STACK_ORDER) -#define STACKFAULT_STACK 1 -#define DOUBLEFAULT_STACK 2 -#define NMI_STACK 3 -#define DEBUG_STACK 4 -#define MCE_STACK 5 -#define N_EXCEPTION_STACKS 5 /* hw limit: 7 */ +#define DOUBLEFAULT_STACK 1 +#define NMI_STACK 2 +#define DEBUG_STACK 3 +#define MCE_STACK 4 +#define N_EXCEPTION_STACKS 4 /* hw limit: 7 */ #define PUD_PAGE_SIZE (_AC(1, UL) << PUD_SHIFT) #define PUD_PAGE_MASK (~(PUD_PAGE_SIZE-1)) diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c index addb207dab92..66e274a3d968 100644 --- a/arch/x86/kernel/dumpstack_64.c +++ b/arch/x86/kernel/dumpstack_64.c @@ -24,7 +24,6 @@ static char x86_stack_ids[][8] = { [ DEBUG_STACK-1 ] = "#DB", [ NMI_STACK-1 ] = "NMI", [ DOUBLEFAULT_STACK-1 ] = "#DF", - [ STACKFAULT_STACK-1 ] = "#SS", [ MCE_STACK-1 ] = "#MC", #if DEBUG_STKSZ > EXCEPTION_STKSZ [ N_EXCEPTION_STACKS ... diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index c2ab43484b5d..e310e82de5e6 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -1510,7 +1510,7 @@ apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \ paranoidzeroentry_ist debug do_debug DEBUG_STACK paranoidzeroentry_ist int3 do_int3 DEBUG_STACK -paranoiderrorentry stack_segment do_stack_segment +errorentry stack_segment do_stack_segment #ifdef CONFIG_XEN zeroentry xen_debug do_debug zeroentry xen_int3 do_int3 diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 8a2684f938b9..b2d6c58b28b0 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -221,28 +221,12 @@ 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_NP, SIGBUS, "segment not present", segment_not_present) -#ifdef CONFIG_X86_32 DO_ERROR(X86_TRAP_SS, SIGBUS, "stack segment", stack_segment) -#endif DO_ERROR_INFO(X86_TRAP_AC, SIGBUS, "alignment check", alignment_check, BUS_ADRALN, 0) #ifdef CONFIG_X86_64 /* 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) { static const char str[] = "double fault"; @@ -776,7 +760,7 @@ void __init trap_init(void) set_intr_gate(X86_TRAP_OLD_MF, &coprocessor_segment_overrun); set_intr_gate(X86_TRAP_TS, &invalid_TSS); 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_SPURIOUS, &spurious_interrupt_bug); set_intr_gate(X86_TRAP_MF, &coprocessor_error); -- 2.1.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/