Re: [PATCH v3 5/6] arm64: add support for uaccess logging

[Dmitry Vyukov]

On Wed, 8 Dec 2021 at 05:48, Peter Collingbourne <pcc@xxxxxxxxxx> wrote:
>
> arm64 does not use CONFIG_GENERIC_ENTRY, so add the support for
> uaccess logging directly to the architecture.
>
> Link: https://linux-review.googlesource.com/id/I88de539fb9c4a9d27fa8cccbe201a6e4382faf89
> Signed-off-by: Peter Collingbourne <pcc@xxxxxxxxxx>
> ---
>  arch/arm64/Kconfig                   | 1 +
>  arch/arm64/include/asm/thread_info.h | 7 ++++++-
>  arch/arm64/kernel/ptrace.c           | 7 +++++++
>  arch/arm64/kernel/signal.c           | 5 +++++
>  arch/arm64/kernel/syscall.c          | 1 +
>  5 files changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index c4207cf9bb17..6023946abe4a 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -161,6 +161,7 @@ config ARM64
>         select HAVE_ARCH_THREAD_STRUCT_WHITELIST
>         select HAVE_ARCH_TRACEHOOK
>         select HAVE_ARCH_TRANSPARENT_HUGEPAGE
> +       select HAVE_ARCH_UACCESS_BUFFER
>         select HAVE_ARCH_VMAP_STACK
>         select HAVE_ARM_SMCCC
>         select HAVE_ASM_MODVERSIONS
> diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
> index e1317b7c4525..0461b36251ea 100644
> --- a/arch/arm64/include/asm/thread_info.h
> +++ b/arch/arm64/include/asm/thread_info.h
> @@ -82,6 +82,8 @@ int arch_dup_task_struct(struct task_struct *dst,
>  #define TIF_SVE_VL_INHERIT     24      /* Inherit SVE vl_onexec across exec */
>  #define TIF_SSBD               25      /* Wants SSB mitigation */
>  #define TIF_TAGGED_ADDR                26      /* Allow tagged user addresses */
> +#define TIF_UACCESS_BUFFER_ENTRY 27     /* thread has non-zero uaccess_desc_addr_addr */
> +#define TIF_UACCESS_BUFFER_EXIT  28     /* thread has non-zero kcur */
>
>  #define _TIF_SIGPENDING                (1 << TIF_SIGPENDING)
>  #define _TIF_NEED_RESCHED      (1 << TIF_NEED_RESCHED)
> @@ -98,6 +100,8 @@ int arch_dup_task_struct(struct task_struct *dst,
>  #define _TIF_SVE               (1 << TIF_SVE)
>  #define _TIF_MTE_ASYNC_FAULT   (1 << TIF_MTE_ASYNC_FAULT)
>  #define _TIF_NOTIFY_SIGNAL     (1 << TIF_NOTIFY_SIGNAL)
> +#define _TIF_UACCESS_BUFFER_ENTRY      (1 << TIF_UACCESS_BUFFER_ENTRY)
> +#define _TIF_UACCESS_BUFFER_EXIT       (1 << TIF_UACCESS_BUFFER_EXIT)
>
>  #define _TIF_WORK_MASK         (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
>                                  _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \
> @@ -106,7 +110,8 @@ int arch_dup_task_struct(struct task_struct *dst,
>
>  #define _TIF_SYSCALL_WORK      (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
>                                  _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
> -                                _TIF_SYSCALL_EMU)
> +                                _TIF_SYSCALL_EMU | _TIF_UACCESS_BUFFER_ENTRY | \
> +                                _TIF_UACCESS_BUFFER_EXIT)
>
>  #ifdef CONFIG_SHADOW_CALL_STACK
>  #define INIT_SCS                                                       \
> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> index 88a9034fb9b5..283372eccaeb 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -29,6 +29,7 @@
>  #include <linux/regset.h>
>  #include <linux/tracehook.h>
>  #include <linux/elf.h>
> +#include <linux/uaccess-buffer.h>
>
>  #include <asm/compat.h>
>  #include <asm/cpufeature.h>
> @@ -1854,6 +1855,9 @@ int syscall_trace_enter(struct pt_regs *regs)
>         if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
>                 trace_sys_enter(regs, regs->syscallno);
>
> +       if (flags & _TIF_UACCESS_BUFFER_ENTRY)
> +               uaccess_buffer_syscall_entry();
> +
>         audit_syscall_entry(regs->syscallno, regs->orig_x0, regs->regs[1],
>                             regs->regs[2], regs->regs[3]);
>
> @@ -1866,6 +1870,9 @@ void syscall_trace_exit(struct pt_regs *regs)
>
>         audit_syscall_exit(regs);
>
> +       if (flags & _TIF_UACCESS_BUFFER_EXIT)
> +               uaccess_buffer_syscall_exit();
> +
>         if (flags & _TIF_SYSCALL_TRACEPOINT)
>                 trace_sys_exit(regs, syscall_get_return_value(current, regs));
>
> diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
> index 8f6372b44b65..5bbd98e5c257 100644
> --- a/arch/arm64/kernel/signal.c
> +++ b/arch/arm64/kernel/signal.c
> @@ -20,6 +20,7 @@
>  #include <linux/tracehook.h>
>  #include <linux/ratelimit.h>
>  #include <linux/syscalls.h>
> +#include <linux/uaccess-buffer.h>
>
>  #include <asm/daifflags.h>
>  #include <asm/debug-monitors.h>
> @@ -919,6 +920,8 @@ static void do_signal(struct pt_regs *regs)
>
>  void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags)
>  {
> +       bool uaccess_buffer_pending = uaccess_buffer_pre_exit_loop();
> +
>         do {
>                 if (thread_flags & _TIF_NEED_RESCHED) {
>                         /* Unmask Debug and SError for the next task */
> @@ -950,6 +953,8 @@ void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags)
>                 local_daif_mask();
>                 thread_flags = READ_ONCE(current_thread_info()->flags);
>         } while (thread_flags & _TIF_WORK_MASK);
> +
> +       uaccess_buffer_post_exit_loop(uaccess_buffer_pending);
>  }
>
>  unsigned long __ro_after_init signal_minsigstksz;
> diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
> index 50a0f1a38e84..d59022b594f2 100644
> --- a/arch/arm64/kernel/syscall.c
> +++ b/arch/arm64/kernel/syscall.c
> @@ -7,6 +7,7 @@
>  #include <linux/ptrace.h>
>  #include <linux/randomize_kstack.h>
>  #include <linux/syscalls.h>
> +#include <linux/uaccess-buffer.h>

This looks strange... Does some other header miss this include?

>
>  #include <asm/daifflags.h>
>  #include <asm/debug-monitors.h>
> --
> 2.34.1.173.g76aa8bc2d0-goog
>