From a798f091113ef4999277dbe0483d37d04fa35b2e Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Wed, 9 Mar 2016 13:24:32 -0800 Subject: [PATCH] x86/entry/32: Change INT80 to be an interrupt gate MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit We want all of the syscall entries to run with interrupts off so that we can efficiently run context tracking before enabling interrupts. This will regress int $0x80 performance on 32-bit kernels by a couple of cycles. This shouldn't matter much -- int $0x80 is not a fast path. This effectively reverts: 657c1eea0019 ("x86/entry/32: Fix entry_INT80_32() to expect interrupts to be on") ... and fixes the same issue differently. Signed-off-by: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: Frédéric Weisbecker Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Paolo Bonzini Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/59b4f90c9ebfccd8c937305dbbbca680bc74b905.1457558566.git.luto@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/entry/common.c | 15 +++------------ arch/x86/entry/entry_32.S | 8 ++++---- arch/x86/entry/entry_64_compat.S | 2 +- arch/x86/kernel/traps.c | 2 +- 4 files changed, 9 insertions(+), 18 deletions(-) diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 209ba334e90f..d69d1b6e6c31 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -371,14 +371,7 @@ __visible void do_syscall_64(struct pt_regs *regs) * in workloads that use it, and it's usually called from * do_fast_syscall_32, so forcibly inline it to improve performance. */ -#ifdef CONFIG_X86_32 -/* 32-bit kernels use a trap gate for INT80, and the asm code calls here. */ -__visible -#else -/* 64-bit kernels use do_syscall_32_irqs_off() instead. */ -static -#endif -__always_inline void do_syscall_32_irqs_on(struct pt_regs *regs) +static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs) { struct thread_info *ti = pt_regs_to_thread_info(regs); unsigned int nr = (unsigned int)regs->orig_ax; @@ -413,14 +406,12 @@ __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs) syscall_return_slowpath(regs); } -#ifdef CONFIG_X86_64 -/* Handles INT80 on 64-bit kernels */ -__visible void do_syscall_32_irqs_off(struct pt_regs *regs) +/* Handles int $0x80 */ +__visible void do_int80_syscall_32(struct pt_regs *regs) { local_irq_enable(); do_syscall_32_irqs_on(regs); } -#endif /* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */ __visible long do_fast_syscall_32(struct pt_regs *regs) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 286efa342091..10868aa734dc 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -463,13 +463,13 @@ ENTRY(entry_INT80_32) SAVE_ALL pt_regs_ax=$-ENOSYS /* save rest */ /* - * User mode is traced as though IRQs are on. Unlike the 64-bit - * case, INT80 is a trap gate on 32-bit kernels, so interrupts - * are already on (unless user code is messing around with iopl). + * User mode is traced as though IRQs are on, and the interrupt gate + * turned them off. */ + TRACE_IRQS_OFF movl %esp, %eax - call do_syscall_32_irqs_on + call do_int80_syscall_32 .Lsyscall_32_done: restore_all: diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S index efe0fe3f76bc..847f2f0c31e5 100644 --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -336,7 +336,7 @@ ENTRY(entry_INT80_compat) TRACE_IRQS_OFF movq %rsp, %rdi - call do_syscall_32_irqs_off + call do_int80_syscall_32 .Lsyscall_32_done: /* Go back to user mode. */ diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 49e2e775f507..5fae2d840e64 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -912,7 +912,7 @@ void __init trap_init(void) #endif #ifdef CONFIG_X86_32 - set_system_trap_gate(IA32_SYSCALL_VECTOR, entry_INT80_32); + set_system_intr_gate(IA32_SYSCALL_VECTOR, entry_INT80_32); set_bit(IA32_SYSCALL_VECTOR, used_vectors); #endif -- 2.20.1