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    Subject[RFC patch 01/15] entry: Provide generic syscall entry functionality
    On syscall entry certain work needs to be done conditionally like tracing,
    seccomp etc. This code is duplicated in all architectures.

    Provide a generic version.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    arch/Kconfig | 3 +
    include/linux/entry-common.h | 122 +++++++++++++++++++++++++++++++++++++++++++
    kernel/Makefile | 1
    kernel/entry/Makefile | 3 +
    kernel/entry/common.c | 33 +++++++++++
    5 files changed, 162 insertions(+)

    --- a/arch/Kconfig
    +++ b/arch/Kconfig
    @@ -27,6 +27,9 @@ config HAVE_IMA_KEXEC
    config HOTPLUG_SMT
    bool

    +config GENERIC_ENTRY
    + bool
    +
    config OPROFILE
    tristate "OProfile system profiling"
    depends on PROFILING
    --- /dev/null
    +++ b/include/linux/entry-common.h
    @@ -0,0 +1,122 @@
    +/* SPDX-License-Identifier: GPL-2.0 */
    +#ifndef __LINUX_ENTRYCOMMON_H
    +#define __LINUX_ENTRYCOMMON_H
    +
    +#include <linux/tracehook.h>
    +#include <linux/syscalls.h>
    +#include <linux/seccomp.h>
    +#include <linux/sched.h>
    +#include <linux/audit.h>
    +
    +#include <asm/entry-common.h>
    +
    +/*
    + * Define dummy _TIF work flags if not defined by the architecture or for
    + * disabled functionality.
    + */
    +#ifndef _TIF_SYSCALL_TRACE
    +# define _TIF_SYSCALL_TRACE (0)
    +#endif
    +
    +#ifndef _TIF_SYSCALL_EMU
    +# define _TIF_SYSCALL_EMU (0)
    +#endif
    +
    +#ifndef _TIF_SYSCALL_TRACEPOINT
    +# define _TIF_SYSCALL_TRACEPOINT (0)
    +#endif
    +
    +#ifndef _TIF_SECCOMP
    +# define _TIF_SECCOMP (0)
    +#endif
    +
    +#ifndef _TIF_AUDIT
    +# define _TIF_AUDIT (0)
    +#endif
    +
    +/*
    + * TIF flags handled in syscall_enter_from_usermode()
    + */
    +#ifndef ARCH_SYSCALL_ENTER_WORK
    +# define ARCH_SYSCALL_ENTER_WORK (0)
    +#endif
    +
    +#define SYSCALL_ENTER_WORK \
    + (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | TIF_SECCOMP | \
    + _TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_EMU | \
    + ARCH_SYSCALL_ENTER_WORK)
    +
    +/**
    + * arch_syscall_enter_tracehook - Wrapper around tracehook_report_syscall_entry()
    + *
    + * Defaults to tracehook_report_syscall_entry(). Can be replaced by
    + * architecture specific code.
    + *
    + * Invoked from syscall_enter_from_usermode()
    + */
    +static inline __must_check int arch_syscall_enter_tracehook(struct pt_regs *regs);
    +
    +#ifndef arch_syscall_enter_tracehook
    +static inline __must_check int arch_syscall_enter_tracehook(struct pt_regs *regs)
    +{
    + return tracehook_report_syscall_entry(regs);
    +}
    +#endif
    +
    +/**
    + * arch_syscall_enter_seccomp - Architecture specific seccomp invocation
    + * @regs: Pointer to currents pt_regs
    + *
    + * Invoked from syscall_enter_from_usermode(). Can be replaced by
    + * architecture specific code.
    + */
    +static inline long arch_syscall_enter_seccomp(struct pt_regs *regs);
    +
    +#ifndef arch_syscall_enter_seccomp
    +static inline long arch_syscall_enter_seccomp(struct pt_regs *regs)
    +{
    + return secure_computing(NULL);
    +}
    +#endif
    +
    +/**
    + * arch_syscall_enter_audit - Architecture specific audit invocation
    + * @regs: Pointer to currents pt_regs
    + *
    + * Invoked from syscall_enter_from_usermode(). Must be replaced by
    + * architecture specific code if the architecture supports audit.
    + */
    +static inline void arch_syscall_enter_audit(struct pt_regs *regs);
    +
    +#ifndef arch_syscall_enter_audit
    +static inline void arch_syscall_enter_audit(struct pt_regs *regs) { }
    +#endif
    +
    +/* Common syscall enter function */
    +long core_syscall_enter_from_usermode(struct pt_regs *regs, long syscall);
    +
    +/**
    + * syscall_enter_from_usermode - Check and handle work before invoking
    + * a syscall
    + * @regs: Pointer to currents pt_regs
    + * @syscall: The syscall number
    + *
    + * Invoked from architecture specific syscall entry code with interrupts
    + * enabled.
    + *
    + * Returns: The original or a modified syscall number
    + */
    +static inline long syscall_enter_from_usermode(struct pt_regs *regs,
    + long syscall)
    +{
    + unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
    +
    + if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
    + BUG_ON(regs != task_pt_regs(current));
    +
    + if (ti_work & SYSCALL_ENTER_WORK)
    + syscall = core_syscall_enter_from_usermode(regs, syscall);
    + return syscall;
    +}
    +
    +#endif
    --- a/kernel/Makefile
    +++ b/kernel/Makefile
    @@ -43,6 +43,7 @@ obj-y += irq/
    obj-y += rcu/
    obj-y += livepatch/
    obj-y += dma/
    +obj-y += entry/

    obj-$(CONFIG_CHECKPOINT_RESTORE) += kcmp.o
    obj-$(CONFIG_FREEZER) += freezer.o
    --- /dev/null
    +++ b/kernel/entry/Makefile
    @@ -0,0 +1,3 @@
    +# SPDX-License-Identifier: GPL-2.0
    +
    +obj-$(CONFIG_GENERIC_ENTRY) += common.o
    --- /dev/null
    +++ b/kernel/entry/common.c
    @@ -0,0 +1,33 @@
    +// SPDX-License-Identifier: GPL-2.0
    +
    +#include <linux/context_tracking.h>
    +#include <linux/entry-common.h>
    +
    +#define CREATE_TRACE_POINTS
    +#include <trace/events/syscalls.h>
    +
    +long core_syscall_enter_from_usermode(struct pt_regs *regs, long syscall)
    +{
    + unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
    + unsigned long ret = 0;
    +
    + if (ti_work & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU)) {
    + ret = arch_syscall_enter_tracehook(regs);
    + if (ret || (ti_work & _TIF_SYSCALL_EMU))
    + return -1L;
    + }
    +
    + /* Do seccomp after ptrace, to catch any tracer changes. */
    + if (ti_work & _TIF_SECCOMP) {
    + ret = arch_syscall_enter_seccomp(regs);
    + if (ret == -1L)
    + return ret;
    + }
    +
    + if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
    + trace_sys_enter(regs, syscall);
    +
    + arch_syscall_enter_audit(regs);
    +
    + return ret ? : syscall;
    +}

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      Last update: 2019-09-19 17:12    [W:4.037 / U:0.448 seconds]
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