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x86/entry/common: Protect against instrumentation
Mark the various syscall entries with noinstr to protect them against instrumentation and add the noinstrumentation_begin()/end() annotations to mark the parts of the functions which are safe to call out into instrumentable code. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200505134340.520277507@linutronix.de
This commit is contained in:
Thomas Gleixner
parent
1723be30e4
commit
8f159f1dfa
@ -41,15 +41,26 @@
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#ifdef CONFIG_CONTEXT_TRACKING
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/* Called on entry from user mode with IRQs off. */
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__visible inline noinstr void enter_from_user_mode(void)
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__visible noinstr void enter_from_user_mode(void)
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{
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CT_WARN_ON(ct_state() != CONTEXT_USER);
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enum ctx_state state = ct_state();
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user_exit_irqoff();
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instrumentation_begin();
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CT_WARN_ON(state != CONTEXT_USER);
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instrumentation_end();
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}
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#else
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static inline void enter_from_user_mode(void) {}
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#endif
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static noinstr void exit_to_user_mode(void)
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{
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user_enter_irqoff();
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mds_user_clear_cpu_buffers();
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}
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static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch)
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{
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#ifdef CONFIG_X86_64
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@ -179,8 +190,7 @@ static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)
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}
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}
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/* Called with IRQs disabled. */
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__visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
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static void __prepare_exit_to_usermode(struct pt_regs *regs)
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{
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struct thread_info *ti = current_thread_info();
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u32 cached_flags;
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@ -219,10 +229,14 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
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*/
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ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);
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#endif
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}
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user_enter_irqoff();
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mds_user_clear_cpu_buffers();
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__visible noinstr void prepare_exit_to_usermode(struct pt_regs *regs)
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{
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instrumentation_begin();
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__prepare_exit_to_usermode(regs);
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instrumentation_end();
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exit_to_user_mode();
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}
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#define SYSCALL_EXIT_WORK_FLAGS \
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@ -251,11 +265,7 @@ static void syscall_slow_exit_work(struct pt_regs *regs, u32 cached_flags)
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tracehook_report_syscall_exit(regs, step);
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}
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/*
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* Called with IRQs on and fully valid regs. Returns with IRQs off in a
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* state such that we can immediately switch to user mode.
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*/
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__visible inline void syscall_return_slowpath(struct pt_regs *regs)
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static void __syscall_return_slowpath(struct pt_regs *regs)
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{
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struct thread_info *ti = current_thread_info();
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u32 cached_flags = READ_ONCE(ti->flags);
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@ -276,15 +286,29 @@ __visible inline void syscall_return_slowpath(struct pt_regs *regs)
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syscall_slow_exit_work(regs, cached_flags);
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local_irq_disable();
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prepare_exit_to_usermode(regs);
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__prepare_exit_to_usermode(regs);
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}
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/*
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* Called with IRQs on and fully valid regs. Returns with IRQs off in a
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* state such that we can immediately switch to user mode.
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*/
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__visible noinstr void syscall_return_slowpath(struct pt_regs *regs)
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{
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instrumentation_begin();
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__syscall_return_slowpath(regs);
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instrumentation_end();
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exit_to_user_mode();
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}
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#ifdef CONFIG_X86_64
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__visible void do_syscall_64(unsigned long nr, struct pt_regs *regs)
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__visible noinstr void do_syscall_64(unsigned long nr, struct pt_regs *regs)
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{
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struct thread_info *ti;
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enter_from_user_mode();
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instrumentation_begin();
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local_irq_enable();
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ti = current_thread_info();
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if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY)
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@ -301,8 +325,10 @@ __visible void do_syscall_64(unsigned long nr, struct pt_regs *regs)
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regs->ax = x32_sys_call_table[nr](regs);
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#endif
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}
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__syscall_return_slowpath(regs);
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syscall_return_slowpath(regs);
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instrumentation_end();
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exit_to_user_mode();
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}
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#endif
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@ -313,7 +339,7 @@ __visible void do_syscall_64(unsigned long nr, struct pt_regs *regs)
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* extremely hot in workloads that use it, and it's usually called from
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* do_fast_syscall_32, so forcibly inline it to improve performance.
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*/
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static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)
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static void do_syscall_32_irqs_on(struct pt_regs *regs)
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{
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struct thread_info *ti = current_thread_info();
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unsigned int nr = (unsigned int)regs->orig_ax;
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@ -337,27 +363,62 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)
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regs->ax = ia32_sys_call_table[nr](regs);
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}
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syscall_return_slowpath(regs);
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__syscall_return_slowpath(regs);
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}
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/* Handles int $0x80 */
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__visible void do_int80_syscall_32(struct pt_regs *regs)
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__visible noinstr void do_int80_syscall_32(struct pt_regs *regs)
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{
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enter_from_user_mode();
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instrumentation_begin();
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local_irq_enable();
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do_syscall_32_irqs_on(regs);
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instrumentation_end();
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exit_to_user_mode();
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}
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static bool __do_fast_syscall_32(struct pt_regs *regs)
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{
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int res;
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/* Fetch EBP from where the vDSO stashed it. */
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if (IS_ENABLED(CONFIG_X86_64)) {
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/*
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* Micro-optimization: the pointer we're following is
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* explicitly 32 bits, so it can't be out of range.
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*/
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res = __get_user(*(u32 *)®s->bp,
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(u32 __user __force *)(unsigned long)(u32)regs->sp);
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} else {
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res = get_user(*(u32 *)®s->bp,
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(u32 __user __force *)(unsigned long)(u32)regs->sp);
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}
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if (res) {
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/* User code screwed up. */
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regs->ax = -EFAULT;
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local_irq_disable();
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__prepare_exit_to_usermode(regs);
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return false;
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}
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/* Now this is just like a normal syscall. */
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do_syscall_32_irqs_on(regs);
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return true;
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}
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/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */
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__visible long do_fast_syscall_32(struct pt_regs *regs)
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__visible noinstr long do_fast_syscall_32(struct pt_regs *regs)
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{
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/*
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* Called using the internal vDSO SYSENTER/SYSCALL32 calling
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* convention. Adjust regs so it looks like we entered using int80.
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*/
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unsigned long landing_pad = (unsigned long)current->mm->context.vdso +
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vdso_image_32.sym_int80_landing_pad;
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vdso_image_32.sym_int80_landing_pad;
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bool success;
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/*
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* SYSENTER loses EIP, and even SYSCALL32 needs us to skip forward
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@ -367,33 +428,17 @@ __visible long do_fast_syscall_32(struct pt_regs *regs)
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regs->ip = landing_pad;
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enter_from_user_mode();
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instrumentation_begin();
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local_irq_enable();
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success = __do_fast_syscall_32(regs);
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/* Fetch EBP from where the vDSO stashed it. */
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if (
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#ifdef CONFIG_X86_64
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/*
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* Micro-optimization: the pointer we're following is explicitly
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* 32 bits, so it can't be out of range.
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*/
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__get_user(*(u32 *)®s->bp,
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(u32 __user __force *)(unsigned long)(u32)regs->sp)
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#else
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get_user(*(u32 *)®s->bp,
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(u32 __user __force *)(unsigned long)(u32)regs->sp)
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#endif
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) {
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instrumentation_end();
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exit_to_user_mode();
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/* User code screwed up. */
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local_irq_disable();
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regs->ax = -EFAULT;
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prepare_exit_to_usermode(regs);
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return 0; /* Keep it simple: use IRET. */
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}
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/* Now this is just like a normal syscall. */
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do_syscall_32_irqs_on(regs);
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/* If it failed, keep it simple: use IRET. */
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if (!success)
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return 0;
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#ifdef CONFIG_X86_64
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/*
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