[PATCH v3 4/6] uaccess-buffer: add CONFIG_GENERIC_ENTRY support

[Dmitry Vyukov]

On Wed, 8 Dec 2021 at 05:48, Peter Collingbourne <pcc at google.com> wrote:
>
> Add uaccess logging support on architectures that use
> CONFIG_GENERIC_ENTRY (currently only s390 and x86).
>
> Link: https://linux-review.googlesource.com/id/I3c5eb19a7e4a1dbe6095f6971f7826c4b0663f7d
> Signed-off-by: Peter Collingbourne <pcc at google.com>

Acked-by: Dmitry Vyukov <dvyukov at google.com>

> ---
>  arch/Kconfig                 |  6 ++++++
>  include/linux/entry-common.h |  2 ++
>  include/linux/thread_info.h  |  4 ++++
>  kernel/entry/common.c        | 10 ++++++++++
>  4 files changed, 22 insertions(+)
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index d3c4ab249e9c..c4dcab5279ac 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -31,6 +31,7 @@ config HOTPLUG_SMT
>         bool
>
>  config GENERIC_ENTRY
> +       select HAVE_ARCH_UACCESS_BUFFER
>         bool
>
>  config KPROBES
> @@ -1312,6 +1313,11 @@ config ARCH_HAS_PARANOID_L1D_FLUSH
>  config DYNAMIC_SIGFRAME
>         bool
>
> +config HAVE_ARCH_UACCESS_BUFFER
> +       bool
> +       help
> +         Select if the architecture's syscall entry/exit code supports uaccess buffers.
> +
>  source "kernel/gcov/Kconfig"
>
>  source "scripts/gcc-plugins/Kconfig"
> diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
> index 2e2b8d6140ed..973fcd1d48a3 100644
> --- a/include/linux/entry-common.h
> +++ b/include/linux/entry-common.h
> @@ -42,12 +42,14 @@
>                                  SYSCALL_WORK_SYSCALL_EMU |             \
>                                  SYSCALL_WORK_SYSCALL_AUDIT |           \
>                                  SYSCALL_WORK_SYSCALL_USER_DISPATCH |   \
> +                                SYSCALL_WORK_UACCESS_BUFFER_ENTRY |    \
>                                  ARCH_SYSCALL_WORK_ENTER)
>  #define SYSCALL_WORK_EXIT      (SYSCALL_WORK_SYSCALL_TRACEPOINT |      \
>                                  SYSCALL_WORK_SYSCALL_TRACE |           \
>                                  SYSCALL_WORK_SYSCALL_AUDIT |           \
>                                  SYSCALL_WORK_SYSCALL_USER_DISPATCH |   \
>                                  SYSCALL_WORK_SYSCALL_EXIT_TRAP |       \
> +                                SYSCALL_WORK_UACCESS_BUFFER_EXIT |     \
>                                  ARCH_SYSCALL_WORK_EXIT)
>
>  /*
> diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
> index ad0c4e041030..b0f8ea86967f 100644
> --- a/include/linux/thread_info.h
> +++ b/include/linux/thread_info.h
> @@ -46,6 +46,8 @@ enum syscall_work_bit {
>         SYSCALL_WORK_BIT_SYSCALL_AUDIT,
>         SYSCALL_WORK_BIT_SYSCALL_USER_DISPATCH,
>         SYSCALL_WORK_BIT_SYSCALL_EXIT_TRAP,
> +       SYSCALL_WORK_BIT_UACCESS_BUFFER_ENTRY,
> +       SYSCALL_WORK_BIT_UACCESS_BUFFER_EXIT,
>  };
>
>  #define SYSCALL_WORK_SECCOMP           BIT(SYSCALL_WORK_BIT_SECCOMP)
> @@ -55,6 +57,8 @@ enum syscall_work_bit {
>  #define SYSCALL_WORK_SYSCALL_AUDIT     BIT(SYSCALL_WORK_BIT_SYSCALL_AUDIT)
>  #define SYSCALL_WORK_SYSCALL_USER_DISPATCH BIT(SYSCALL_WORK_BIT_SYSCALL_USER_DISPATCH)
>  #define SYSCALL_WORK_SYSCALL_EXIT_TRAP BIT(SYSCALL_WORK_BIT_SYSCALL_EXIT_TRAP)
> +#define SYSCALL_WORK_UACCESS_BUFFER_ENTRY      BIT(SYSCALL_WORK_BIT_UACCESS_BUFFER_ENTRY)
> +#define SYSCALL_WORK_UACCESS_BUFFER_EXIT       BIT(SYSCALL_WORK_BIT_UACCESS_BUFFER_EXIT)
>  #endif
>
>  #include <asm/thread_info.h>
> diff --git a/kernel/entry/common.c b/kernel/entry/common.c
> index d5a61d565ad5..57c4bb01a554 100644
> --- a/kernel/entry/common.c
> +++ b/kernel/entry/common.c
> @@ -6,6 +6,7 @@
>  #include <linux/livepatch.h>
>  #include <linux/audit.h>
>  #include <linux/tick.h>
> +#include <linux/uaccess-buffer.h>
>
>  #include "common.h"
>
> @@ -70,6 +71,9 @@ static long syscall_trace_enter(struct pt_regs *regs, long syscall,
>                         return ret;
>         }
>
> +       if (work & SYSCALL_WORK_UACCESS_BUFFER_ENTRY)
> +               uaccess_buffer_syscall_entry();
> +
>         /* Either of the above might have changed the syscall number */
>         syscall = syscall_get_nr(current, regs);
>
> @@ -197,14 +201,17 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
>  static void exit_to_user_mode_prepare(struct pt_regs *regs)
>  {
>         unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
> +       bool uaccess_buffer_pending;
>
>         lockdep_assert_irqs_disabled();
>
>         /* Flush pending rcuog wakeup before the last need_resched() check */
>         tick_nohz_user_enter_prepare();
>
> +       uaccess_buffer_pending = uaccess_buffer_pre_exit_loop();
>         if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
>                 ti_work = exit_to_user_mode_loop(regs, ti_work);
> +       uaccess_buffer_post_exit_loop(uaccess_buffer_pending);
>
>         arch_exit_to_user_mode_prepare(regs, ti_work);
>
> @@ -247,6 +254,9 @@ static void syscall_exit_work(struct pt_regs *regs, unsigned long work)
>
>         audit_syscall_exit(regs);
>
> +       if (work & SYSCALL_WORK_UACCESS_BUFFER_EXIT)
> +               uaccess_buffer_syscall_exit();
> +
>         if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT)
>                 trace_sys_exit(regs, syscall_get_return_value(current, regs));
>
> --
> 2.34.1.173.g76aa8bc2d0-goog
>