Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751339AbaLQP42 (ORCPT ); Wed, 17 Dec 2014 10:56:28 -0500 Received: from mail.skyhub.de ([78.46.96.112]:41146 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750994AbaLQP40 (ORCPT ); Wed, 17 Dec 2014 10:56:26 -0500 Date: Wed, 17 Dec 2014 16:56:22 +0100 From: Borislav Petkov To: Jiri Slaby , Andy Lutomirski Cc: stable@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds Subject: Re: [PATCH 3.12 14/66] x86_64, traps: Stop using IST for #SS Message-ID: <20141217155622.GA9416@pd.tnic> References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Dec 06, 2014 at 04:07:06PM +0100, Jiri Slaby wrote: > 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); I guess this should say "&stack_segment" in order for it to be consistent with the rest of the set_intr_gate() calls here. Fortunately, this is not an issue as function designators are automatically promoted to function pointers, as the identical asm shows: .loc 1 792 0 movq $stack_segment, %rsi #, movl $12, %edi #, call set_intr_gate # .loc 1 792 0 movq $stack_segment, %rsi #, movl $12, %edi #, call set_intr_gate # -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. -- -- 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/