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142781e108
On syscall entry certain work needs to be done: - Establish state (lockdep, context tracking, tracing) - Conditional work (ptrace, seccomp, audit...) This code is needlessly duplicated and different in all architectures. Provide a generic version based on the x86 implementation which has all the RCU and instrumentation bits right. As interrupt/exception entry from user space needs parts of the same functionality, provide a function for this as well. syscall_enter_from_user_mode() and irqentry_enter_from_user_mode() must be called right after the low level ASM entry. The calling code must be non-instrumentable. After the functions returns state is correct and the subsequent functions can be instrumented. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Kees Cook <keescook@chromium.org> Link: https://lkml.kernel.org/r/20200722220519.513463269@linutronix.de
88 lines
2.1 KiB
C
88 lines
2.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/context_tracking.h>
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#include <linux/entry-common.h>
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#define CREATE_TRACE_POINTS
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#include <trace/events/syscalls.h>
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/**
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* enter_from_user_mode - Establish state when coming from user mode
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*
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* Syscall/interrupt entry disables interrupts, but user mode is traced as
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* interrupts enabled. Also with NO_HZ_FULL RCU might be idle.
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*
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* 1) Tell lockdep that interrupts are disabled
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* 2) Invoke context tracking if enabled to reactivate RCU
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* 3) Trace interrupts off state
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*/
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static __always_inline void enter_from_user_mode(struct pt_regs *regs)
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{
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arch_check_user_regs(regs);
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lockdep_hardirqs_off(CALLER_ADDR0);
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CT_WARN_ON(ct_state() != CONTEXT_USER);
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user_exit_irqoff();
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instrumentation_begin();
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trace_hardirqs_off_finish();
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instrumentation_end();
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}
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static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
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{
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if (unlikely(audit_context())) {
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unsigned long args[6];
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syscall_get_arguments(current, regs, args);
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audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
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}
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}
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static long syscall_trace_enter(struct pt_regs *regs, long syscall,
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unsigned long ti_work)
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{
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long ret = 0;
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/* Handle ptrace */
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if (ti_work & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU)) {
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ret = arch_syscall_enter_tracehook(regs);
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if (ret || (ti_work & _TIF_SYSCALL_EMU))
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return -1L;
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}
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/* Do seccomp after ptrace, to catch any tracer changes. */
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if (ti_work & _TIF_SECCOMP) {
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ret = __secure_computing(NULL);
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if (ret == -1L)
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return ret;
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}
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if (unlikely(ti_work & _TIF_SYSCALL_TRACEPOINT))
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trace_sys_enter(regs, syscall);
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syscall_enter_audit(regs, syscall);
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return ret ? : syscall;
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}
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noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
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{
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unsigned long ti_work;
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enter_from_user_mode(regs);
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instrumentation_begin();
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local_irq_enable();
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ti_work = READ_ONCE(current_thread_info()->flags);
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if (ti_work & SYSCALL_ENTER_WORK)
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syscall = syscall_trace_enter(regs, syscall, ti_work);
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instrumentation_end();
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return syscall;
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}
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noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
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{
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enter_from_user_mode(regs);
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}
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