Re: [PATCH v4 06/34] x86/arm: Add BUGFRAME_NR define and BUILD checks.

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 15/03/16 17:56, Konrad Rzeszutek Wilk wrote:
> So that we have a nice mechansim to figure out the upper
> bounds of bug.frames and also catch compiler errors in case
> one tries to use a higher frame number.
>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>
> ---
> Cc: Stefano Stabellini <stefano.stabellini@citrix.com>
> Cc: Julien Grall <julien.grall@arm.com>
> Cc: Keir Fraser <keir@xen.org>
> Cc: Jan Beulich <jbeulich@suse.com>
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> ---
> ---
>  xen/include/asm-arm/bug.h | 2 ++
>  xen/include/asm-x86/bug.h | 3 ++-
>  2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/xen/include/asm-arm/bug.h b/xen/include/asm-arm/bug.h
> index ab9e811..4df6b2a 100644
> --- a/xen/include/asm-arm/bug.h
> +++ b/xen/include/asm-arm/bug.h
> @@ -31,6 +31,7 @@ struct bug_frame {
>  #define BUGFRAME_warn   0
>  #define BUGFRAME_bug    1
>  #define BUGFRAME_assert 2
> +#define BUGFRAME_NR     3
>  
>  /* Many versions of GCC doesn't support the asm %c parameter which would
>   * be preferable to this unpleasantness. We use mergeable string
> @@ -39,6 +40,7 @@ struct bug_frame {
>   */
>  #define BUG_FRAME(type, line, file, has_msg, msg) do {                      \
>      BUILD_BUG_ON((line) >> 16);                                             \
> +    BUILD_BUG_ON(type >= BUGFRAME_NR);                                      \
>      asm ("1:"BUG_INSTR"\n"                                                  \
>           ".pushsection .rodata.str, \"aMS\", %progbits, 1\n"                \
>           "2:\t.asciz " __stringify(file) "\n"                               \
> diff --git a/xen/include/asm-x86/bug.h b/xen/include/asm-x86/bug.h
> index e868e85..bd17ade 100644
> --- a/xen/include/asm-x86/bug.h
> +++ b/xen/include/asm-x86/bug.h
> @@ -9,7 +9,7 @@
>  #define BUGFRAME_warn   1
>  #define BUGFRAME_bug    2
>  #define BUGFRAME_assert 3
> -
> +#define BUGFRAME_NR     4
>  #ifndef __ASSEMBLY__
>  
>  struct bug_frame {
> @@ -51,6 +51,7 @@ struct bug_frame {
>  
>  #define BUG_FRAME(type, line, ptr, second_frame, msg) do {                   \
>      BUILD_BUG_ON((line) >> (BUG_LINE_LO_WIDTH + BUG_LINE_HI_WIDTH));         \
> +    BUILD_BUG_ON((type) >= (BUGFRAME_NR));                                   \
>      asm volatile ( _ASM_BUGFRAME_TEXT(second_frame)                          \
>                     :: _ASM_BUGFRAME_INFO(type, line, ptr, msg) );            \
>  } while (0)

Please fold this hunk in as well,

diff --git a/xen/include/asm-x86/bug.h b/xen/include/asm-x86/bug.h
index e868e85..5f9032e 100644
--- a/xen/include/asm-x86/bug.h
+++ b/xen/include/asm-x86/bug.h
@@ -83,6 +83,11 @@ extern const struct bug_frame __start_bug_frames[],
  * in .rodata
  */
     .macro BUG_FRAME type, line, file_str, second_frame, msg
+
+    .if \type >= BUGFRAME_NR
+         .error "Invalid BUGFRAME index"
+    .endif
+
     .L\@ud: ud2a
 
     .pushsection .rodata.str1, "aMS", @progbits, 1

Which is an equivalent check for ASM bugframes.

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

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