[PATCH 5.11 029/210] gcov: re-fix clang-11+ support

Greg Kroah-Hartman
2021-04-12T09:22:19Z

From: Nick Desaulniers <ndesaulniers@google.com>

commit 9562fd132985ea9185388a112e50f2a51557827d upstream.

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 .gcda -- gcno= .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
Link: https://lkml.kernel.org/r/20210408184631.1156669-1-ndesaulniers@google.com
Reported-by: Prasad Sodagudi <psodagud@quicinc.com>
Tested-by: Prasad Sodagudi <psodagud@quicinc.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Cc: <stable@vger.kernel.org> [5.4+]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
kernel/gcov/clang.c | 29 +++++++++++++++++++----------
1 file changed, 19 insertions(+), 10 deletions(-)

--- a/kernel/gcov/clang.c
+++ b/kernel/gcov/clang.c
@@ -70,7 +70,9 @@ struct gcov_fn_info {

u32 ident;
u32 checksum;
+#if CONFIG_CLANG_VERSION < 110000
u8 use_extra_checksum;
+#endif
u32 cfg_checksum;

u32 num_counters;
@@ -145,10 +147,8 @@ void llvm_gcda_emit_function(u32 ident,

list_add_tail(&info->head, &current_info->functions);
}
-EXPORT_SYMBOL(llvm_gcda_emit_function);
#else
-void llvm_gcda_emit_function(u32 ident, u32 func_checksum,
- u8 use_extra_checksum, u32 cfg_checksum)
+void llvm_gcda_emit_function(u32 ident, u32 func_checksum, u32 cfg_checksum)
{
struct gcov_fn_info *info = kzalloc(sizeof(*info), GFP_KERNEL);

@@ -158,12 +158,11 @@ void llvm_gcda_emit_function(u32 ident,
INIT_LIST_HEAD(&info->head);
info->ident = ident;
info->checksum = func_checksum;
- info->use_extra_checksum = use_extra_checksum;
info->cfg_checksum = cfg_checksum;
list_add_tail(&info->head, &current_info->functions);
}
-EXPORT_SYMBOL(llvm_gcda_emit_function);
#endif
+EXPORT_SYMBOL(llvm_gcda_emit_function);

void llvm_gcda_emit_arcs(u32 num_counters, u64 *counters)
{
@@ -293,11 +292,16 @@ int gcov_info_is_compatible(struct gcov_
!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);
}
@@ -529,17 +533,22 @@ static size_t convert_to_gcda(char *buff

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);