On Wed, Apr 07, 2021 at 11:54:55AM -0700, Nick Desaulniers wrote:
> LLVM changed the expected function signature for
> llvm_gcda_emit_function() in the clang-11 release. Users of clang-11 or
> newer may have noticed their kernels producing invalid coverage
> information:
>
> $ llvm-cov gcov -a -c -u -f -b <input>.gcda -- gcno=<input>.gcno
> 1 <func>: checksum mismatch, \
> (<lineno chksum A>, <cfg chksum B>) != (<lineno chksum A>, <cfg chksum C>)
> 2 Invalid .gcda File!
> ...
>
> Fix up the function signatures so calling this function interprets its
> parameters correctly and computes the correct cfg checksum. In
> particular, in clang-11, the additional checksum is no longer optional.
>
> Link: https://reviews.llvm.org/rG25544ce2df0daa4304c07e64b9c8b0f7df60c11d
> Cc: sta...@vger.kernel.org #5.4+
> Reported-by: Prasad Sodagudi <psoda...@quicinc.com>
> Tested-by: Prasad Sodagudi <psoda...@quicinc.com>
> Signed-off-by: Nick Desaulniers <ndesaulni...@google.com>
Reviewed-by: Nathan Chancellor <nat...@kernel.org>
> ---
> kernel/gcov/clang.c | 38 +++++++++++++++++++++++++++++++++-----
> 1 file changed, 33 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/gcov/clang.c b/kernel/gcov/clang.c
> index d41f5ecda9db..1747204541bf 100644
> --- a/kernel/gcov/clang.c
> +++ b/kernel/gcov/clang.c
> @@ -69,7 +69,9 @@ struct gcov_fn_info {
>
> u32 ident;
> u32 checksum;
> +#if CONFIG_CLANG_VERSION < 110000
> u8 use_extra_checksum;
> +#endif
> u32 cfg_checksum;
>
> u32 num_counters;
> @@ -111,6 +113,7 @@ void llvm_gcda_start_file(const char *orig_filename, u32
> version, u32 checksum)
> }
> EXPORT_SYMBOL(llvm_gcda_start_file);
>
> +#if CONFIG_CLANG_VERSION < 110000
> void llvm_gcda_emit_function(u32 ident, u32 func_checksum,
> u8 use_extra_checksum, u32 cfg_checksum)
> {
> @@ -126,6 +129,21 @@ void llvm_gcda_emit_function(u32 ident, u32
> func_checksum,
> info->cfg_checksum = cfg_checksum;
> list_add_tail(&info->head, ¤t_info->functions);
> }
> +#else
> +void llvm_gcda_emit_function(u32 ident, u32 func_checksum, u32 cfg_checksum)
> +{
> + struct gcov_fn_info *info = kzalloc(sizeof(*info), GFP_KERNEL);
> +
> + if (!info)
> + return;
> +
> + INIT_LIST_HEAD(&info->head);
> + info->ident = ident;
> + info->checksum = func_checksum;
> + info->cfg_checksum = cfg_checksum;
> + list_add_tail(&info->head, ¤t_info->functions);
> +}
> +#endif
> EXPORT_SYMBOL(llvm_gcda_emit_function);
>
> void llvm_gcda_emit_arcs(u32 num_counters, u64 *counters)
> @@ -256,11 +274,16 @@ int gcov_info_is_compatible(struct gcov_info *info1,
> struct gcov_info *info2)
> !list_is_last(&fn_ptr2->head, &info2->functions)) {
> if (fn_ptr1->checksum != fn_ptr2->checksum)
> return false;
> +#if CONFIG_CLANG_VERSION < 110000
> if (fn_ptr1->use_extra_checksum != fn_ptr2->use_extra_checksum)
> return false;
> if (fn_ptr1->use_extra_checksum &&
> fn_ptr1->cfg_checksum != fn_ptr2->cfg_checksum)
> return false;
> +#else
> + if (fn_ptr1->cfg_checksum != fn_ptr2->cfg_checksum)
> + return false;
> +#endif
> fn_ptr1 = list_next_entry(fn_ptr1, head);
> fn_ptr2 = list_next_entry(fn_ptr2, head);
> }
> @@ -378,17 +401,22 @@ size_t convert_to_gcda(char *buffer, struct gcov_info
> *info)
>
> list_for_each_entry(fi_ptr, &info->functions, head) {
> u32 i;
> - u32 len = 2;
> -
> - if (fi_ptr->use_extra_checksum)
> - len++;
>
> pos += store_gcov_u32(buffer, pos, GCOV_TAG_FUNCTION);
> - pos += store_gcov_u32(buffer, pos, len);
> +#if CONFIG_CLANG_VERSION < 110000
> + pos += store_gcov_u32(buffer, pos,
> + fi_ptr->use_extra_checksum ? 3 : 2);
> +#else
> + pos += store_gcov_u32(buffer, pos, 3);
> +#endif
> pos += store_gcov_u32(buffer, pos, fi_ptr->ident);
> pos += store_gcov_u32(buffer, pos, fi_ptr->checksum);
> +#if CONFIG_CLANG_VERSION < 110000
> if (fi_ptr->use_extra_checksum)
> pos += store_gcov_u32(buffer, pos,
> fi_ptr->cfg_checksum);
> +#else
> + pos += store_gcov_u32(buffer, pos, fi_ptr->cfg_checksum);
> +#endif
>
> pos += store_gcov_u32(buffer, pos, GCOV_TAG_COUNTER_BASE);
> pos += store_gcov_u32(buffer, pos, fi_ptr->num_counters * 2);
> --
> 2.31.1.295.g9ea45b61b8-goog
>
