[PATCH 1/2] gcov: re-fix clang-11+ support

[PATCH 1/2] gcov: re-fix clang-11+ support

[Nick Desaulniers]

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: stable@vger.kernel.org #5.4+
Reported-by: Prasad Sodagudi <psodagud@quicinc.com>
Tested-by: Prasad Sodagudi <psodagud@quicinc.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
 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, &current_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, &current_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

Re: [PATCH 1/2] gcov: re-fix clang-11+ support

[Nathan Chancellor]

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: stable@vger.kernel.org #5.4+
> 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>

> ---
>  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, &current_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, &current_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
> 

Re: [PATCH 1/2] gcov: re-fix clang-11+ support

[Andrew Morton]

On Wed,  7 Apr 2021 11:54:55 -0700 Nick Desaulniers <ndesaulniers@google.com> 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.

Which tree is this against?  I'm seeing quite a lot of rejects against
Linus's current.

Re: [PATCH 1/2] gcov: re-fix clang-11+ support

[Nick Desaulniers]

On Wed, Apr 7, 2021 at 2:21 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Wed,  7 Apr 2021 11:54:55 -0700 Nick Desaulniers <ndesaulniers@google.com> 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.
>
> Which tree is this against?  I'm seeing quite a lot of rejects against
> Linus's current.

Today's linux-next; the only recent changes to this single source file
since my last patches were:

commit b3c4e66c908b ("gcov: combine common code")
commit 17d0508a080d ("gcov: use kvmalloc()")

both have your sign off, so I assume those are in your tree?

-- 
Thanks,
~Nick Desaulniers

Re: [PATCH 1/2] gcov: re-fix clang-11+ support

[Andrew Morton]

On Wed, 7 Apr 2021 14:28:21 -0700 Nick Desaulniers <ndesaulniers@google.com> wrote:

> On Wed, Apr 7, 2021 at 2:21 PM Andrew Morton <akpm@linux-foundation.org> wrote:
> >
> > On Wed,  7 Apr 2021 11:54:55 -0700 Nick Desaulniers <ndesaulniers@google.com> 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.
> >
> > Which tree is this against?  I'm seeing quite a lot of rejects against
> > Linus's current.
> 
> Today's linux-next; the only recent changes to this single source file
> since my last patches were:
> 
> commit b3c4e66c908b ("gcov: combine common code")
> commit 17d0508a080d ("gcov: use kvmalloc()")
> 
> both have your sign off, so I assume those are in your tree?

Yes, I presently have

gcov-clang-drop-support-for-clang-10-and-older.patch
gcov-combine-common-code.patch
gcov-simplify-buffer-allocation.patch
gcov-use-kvmalloc.patch

But this patch ("gcov: re-fix clang-11+ support") has cc:stable, so it
should be against Linus's tree, to give the -stable trees something
more mergeable.

[PATCH v2] gcov: re-fix clang-11+ support

[Nick Desaulniers]

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: stable@vger.kernel.org #5.4+
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>
---
Changes V1 -> V2:
* Carried Nathan's reviewed-by tag.
* Rebased on mainline, as per Andrew.
* Left off patch 2/2 from the series
https://lore.kernel.org/lkml/20210407185456.41943-1-ndesaulniers@google.com/
  I assume that dropping support for clang-10+GCOV will be held
  separately for -next for 5.13, while this will be sent for 5.12?

 kernel/gcov/clang.c | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/kernel/gcov/clang.c b/kernel/gcov/clang.c
index 8743150db2ac..c466c7fbdece 100644
--- 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, const char *function_name,
 
 	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, u32 func_checksum,
 	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_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);
 	}
@@ -529,17 +533,22 @@ static 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);

base-commit: 3fb4f979b4fa1f92a02b538ae86e725b73e703d0
-- 
2.31.1.295.g9ea45b61b8-goog