On Thu, Dec 07, 2023 at 01:08:27PM +0100, Ilya Leoshkevich wrote:
> GCC can emit code between the function label and the .LASANPC label,
> making the latter unaligned. Some architectures cannot load unaligned
> labels directly and require literal pool entries, which is inefficient.
>
> Move the invocation of asan_function_start to
> ASM_OUTPUT_FUNCTION_LABEL, which guarantees that no additional code is
> emitted. This allows setting the .LASANPC label alignment to the
> respective function alignment.
> --- a/gcc/output.h
> +++ b/gcc/output.h
> @@ -178,6 +178,10 @@ extern void assemble_asm (tree);
> /* Get the function's name from a decl, as described by its RTL. */
> extern const char *get_fnname_from_decl (tree);
>
> +/* Output function label, possibly with accompanying metadata. No additional
> + code or data is output after the label. */
Please copy the above comment also
> --- a/gcc/varasm.cc
> +++ b/gcc/varasm.cc
> @@ -61,6 +61,7 @@ along with GCC; see the file COPYING3. If not see
> #include "alloc-pool.h"
> #include "toplev.h"
> #include "opts.h"
> +#include "asan.h"
>
> /* The (assembler) name of the first globally-visible object output. */
> extern GTY(()) const char *first_global_object_name;
> @@ -1835,6 +1836,15 @@ get_fnname_from_decl (tree decl)
> return XSTR (x, 0);
> }
>
here.
> +void assemble_function_label_raw (FILE *file, const char *name)
Also, newline rather than space after void.
> +{
> + ASM_OUTPUT_LABEL (file, name);
> + if ((flag_sanitize & SANITIZE_ADDRESS)
> + /* Notify ASAN only about the first function label. */
> + && (in_cold_section_p == first_function_block_is_cold))
> + asan_function_start ();
> +}
With this the asan.cc/varasm.cc changes look good to me, for the rest I'd
prefer to hear what Jeff says.
Jakub
