Re: [PATCH 1/1] mm/kasan: use {READ,WRITE}_MODE not true,false

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On Sun, Jun 5, 2016 at 1:11 PM, seokhoon.yoon <iamyooon@xxxxxxxxx> wrote:
> When Kasan tell memory access is write or not, use true or false.
> This expression is simple and convenient.
>
> But I think it is possible to more readable. and so change it.
>
> Signed-off-by: seokhoon.yoon <iamyooon@xxxxxxxxx>
> ---
>  mm/kasan/kasan.c  | 32 ++++++++++++++++----------------
>  mm/kasan/kasan.h  | 12 ++++++++++--
>  mm/kasan/report.c | 16 ++++++++--------
>  3 files changed, 34 insertions(+), 26 deletions(-)
>
> diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
> index 18b6a2b..642d936 100644
> --- a/mm/kasan/kasan.c
> +++ b/mm/kasan/kasan.c
> @@ -274,7 +274,7 @@ static __always_inline bool memory_is_poisoned(unsigned long addr, size_t size)
>  }
>
>  static __always_inline void check_memory_region_inline(unsigned long addr,
> -                                               size_t size, bool write,
> +                                               size_t size, enum acc_type type,
>                                                 unsigned long ret_ip)
>  {
>         if (unlikely(size == 0))
> @@ -282,39 +282,39 @@ static __always_inline void check_memory_region_inline(unsigned long addr,
>
>         if (unlikely((void *)addr <
>                 kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
> -               kasan_report(addr, size, write, ret_ip);
> +               kasan_report(addr, size, type, ret_ip);
>                 return;
>         }
>
>         if (likely(!memory_is_poisoned(addr, size)))
>                 return;
>
> -       kasan_report(addr, size, write, ret_ip);
> +       kasan_report(addr, size, type, ret_ip);
>  }
>
>  static void check_memory_region(unsigned long addr,
> -                               size_t size, bool write,
> +                               size_t size, enum acc_type type,
>                                 unsigned long ret_ip)
>  {
> -       check_memory_region_inline(addr, size, write, ret_ip);
> +       check_memory_region_inline(addr, size, type, ret_ip);
>  }
>
>  void kasan_check_read(const void *p, unsigned int size)
>  {
> -       check_memory_region((unsigned long)p, size, false, _RET_IP_);
> +       check_memory_region((unsigned long)p, size, READ_MODE, _RET_IP_);
>  }
>  EXPORT_SYMBOL(kasan_check_read);
>
>  void kasan_check_write(const void *p, unsigned int size)
>  {
> -       check_memory_region((unsigned long)p, size, true, _RET_IP_);
> +       check_memory_region((unsigned long)p, size, WRITE_MODE, _RET_IP_);
>  }
>  EXPORT_SYMBOL(kasan_check_write);
>
>  #undef memset
>  void *memset(void *addr, int c, size_t len)
>  {
> -       check_memory_region((unsigned long)addr, len, true, _RET_IP_);
> +       check_memory_region((unsigned long)addr, len, WRITE_MODE, _RET_IP_);
>
>         return __memset(addr, c, len);
>  }
> @@ -322,8 +322,8 @@ void *memset(void *addr, int c, size_t len)
>  #undef memmove
>  void *memmove(void *dest, const void *src, size_t len)
>  {
> -       check_memory_region((unsigned long)src, len, false, _RET_IP_);
> -       check_memory_region((unsigned long)dest, len, true, _RET_IP_);
> +       check_memory_region((unsigned long)src, len, READ_MODE, _RET_IP_);
> +       check_memory_region((unsigned long)dest, len, WRITE_MODE, _RET_IP_);
>
>         return __memmove(dest, src, len);
>  }
> @@ -331,8 +331,8 @@ void *memmove(void *dest, const void *src, size_t len)
>  #undef memcpy
>  void *memcpy(void *dest, const void *src, size_t len)
>  {
> -       check_memory_region((unsigned long)src, len, false, _RET_IP_);
> -       check_memory_region((unsigned long)dest, len, true, _RET_IP_);
> +       check_memory_region((unsigned long)src, len, READ_MODE, _RET_IP_);
> +       check_memory_region((unsigned long)dest, len, WRITE_MODE, _RET_IP_);
>
>         return __memcpy(dest, src, len);
>  }
> @@ -709,7 +709,7 @@ EXPORT_SYMBOL(__asan_unregister_globals);
>  #define DEFINE_ASAN_LOAD_STORE(size)                                   \
>         void __asan_load##size(unsigned long addr)                      \
>         {                                                               \
> -               check_memory_region_inline(addr, size, false, _RET_IP_);\
> +               check_memory_region_inline(addr, size, READ_MODE, _RET_IP_);\
>         }                                                               \
>         EXPORT_SYMBOL(__asan_load##size);                               \
>         __alias(__asan_load##size)                                      \
> @@ -717,7 +717,7 @@ EXPORT_SYMBOL(__asan_unregister_globals);
>         EXPORT_SYMBOL(__asan_load##size##_noabort);                     \
>         void __asan_store##size(unsigned long addr)                     \
>         {                                                               \
> -               check_memory_region_inline(addr, size, true, _RET_IP_); \
> +               check_memory_region_inline(addr, size, WRITE_MODE, _RET_IP_);\
>         }                                                               \
>         EXPORT_SYMBOL(__asan_store##size);                              \
>         __alias(__asan_store##size)                                     \
> @@ -732,7 +732,7 @@ DEFINE_ASAN_LOAD_STORE(16);
>
>  void __asan_loadN(unsigned long addr, size_t size)
>  {
> -       check_memory_region(addr, size, false, _RET_IP_);
> +       check_memory_region(addr, size, READ_MODE, _RET_IP_);
>  }
>  EXPORT_SYMBOL(__asan_loadN);
>
> @@ -742,7 +742,7 @@ EXPORT_SYMBOL(__asan_loadN_noabort);
>
>  void __asan_storeN(unsigned long addr, size_t size)
>  {
> -       check_memory_region(addr, size, true, _RET_IP_);
> +       check_memory_region(addr, size, WRITE_MODE, _RET_IP_);
>  }
>  EXPORT_SYMBOL(__asan_storeN);
>
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 7f7ac51..47cb58c 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -27,11 +27,19 @@
>  #define KASAN_ABI_VERSION 1
>  #endif
>
> +/*
> + * Distinguish memory access
> + */
> +enum acc_type {
> +       READ_MODE,
> +       WRITE_MODE
> +};
> +
>  struct kasan_access_info {
>         const void *access_addr;
>         const void *first_bad_addr;
>         size_t access_size;
> -       bool is_write;
> +       enum acc_type access_type;
>         unsigned long ip;
>  };
>
> @@ -109,7 +117,7 @@ static inline bool kasan_report_enabled(void)
>  }
>
>  void kasan_report(unsigned long addr, size_t size,
> -               bool is_write, unsigned long ip);
> +               enum acc_type type, unsigned long ip);
>
>  #ifdef CONFIG_SLAB
>  void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache);
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index b3c122d..e0bee22 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -96,7 +96,7 @@ static void print_error_description(struct kasan_access_info *info)
>                 bug_type, (void *)info->ip,
>                 info->access_addr);
>         pr_err("%s of size %zu by task %s/%d\n",
> -               info->is_write ? "Write" : "Read",
> +               info->access_type == WRITE_MODE ? "Write" : "Read",
>                 info->access_size, current->comm, task_pid_nr(current));
>  }
>
> @@ -267,7 +267,7 @@ static void kasan_report_error(struct kasan_access_info *info)
>                 pr_err("BUG: KASAN: %s on address %p\n",
>                         bug_type, info->access_addr);
>                 pr_err("%s of size %zu by task %s/%d\n",
> -                       info->is_write ? "Write" : "Read",
> +                       info->access_type == WRITE_MODE ? "Write" : "Read",
>                         info->access_size, current->comm,
>                         task_pid_nr(current));
>                 dump_stack();
> @@ -283,7 +283,7 @@ static void kasan_report_error(struct kasan_access_info *info)
>  }
>
>  void kasan_report(unsigned long addr, size_t size,
> -               bool is_write, unsigned long ip)
> +               enum acc_type type, unsigned long ip)
>  {
>         struct kasan_access_info info;
>
> @@ -292,7 +292,7 @@ void kasan_report(unsigned long addr, size_t size,
>
>         info.access_addr = (void *)addr;
>         info.access_size = size;
> -       info.is_write = is_write;
> +       info.access_type = type;
>         info.ip = ip;
>
>         kasan_report_error(&info);
> @@ -302,14 +302,14 @@ void kasan_report(unsigned long addr, size_t size,
>  #define DEFINE_ASAN_REPORT_LOAD(size)                     \
>  void __asan_report_load##size##_noabort(unsigned long addr) \
>  {                                                         \
> -       kasan_report(addr, size, false, _RET_IP_);        \
> +       kasan_report(addr, size, READ_MODE, _RET_IP_);    \
>  }                                                         \
>  EXPORT_SYMBOL(__asan_report_load##size##_noabort)
>
>  #define DEFINE_ASAN_REPORT_STORE(size)                     \
>  void __asan_report_store##size##_noabort(unsigned long addr) \
>  {                                                          \
> -       kasan_report(addr, size, true, _RET_IP_);          \
> +       kasan_report(addr, size, WRITE_MODE, _RET_IP_);    \
>  }                                                          \
>  EXPORT_SYMBOL(__asan_report_store##size##_noabort)
>
> @@ -326,12 +326,12 @@ DEFINE_ASAN_REPORT_STORE(16);
>
>  void __asan_report_load_n_noabort(unsigned long addr, size_t size)
>  {
> -       kasan_report(addr, size, false, _RET_IP_);
> +       kasan_report(addr, size, READ_MODE, _RET_IP_);
>  }
>  EXPORT_SYMBOL(__asan_report_load_n_noabort);
>
>  void __asan_report_store_n_noabort(unsigned long addr, size_t size)
>  {
> -       kasan_report(addr, size, true, _RET_IP_);
> +       kasan_report(addr, size, WRITE_MODE, _RET_IP_);
>  }
>  EXPORT_SYMBOL(__asan_report_store_n_noabort);


Hello seokhoon.yoon,


Where exactly do you hit readability problems?
I would say that the only problematic place is where we initialize the value:

    kasan_report(addr, size, true, _RET_IP_);
    check_memory_region(addr, size, true, _RET_IP_);

Here it is really difficult to say what true/false mean. Even if you
know that it is access type, you don't necessary remember if true
means write or read. That could be solved by adding comments:

    kasan_report(addr, size, /* write = */ true, _RET_IP_);

In all other places one sees that we are talking about "write".

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