Re: [PATCH v2 1/2] gcov: fix clang-11+ support

On Fri, Mar 12, 2021 at 02:41:31PM -0800, Nick Desaulniers wrote:

LLVM changed the expected function signatures for llvm_gcda_start_file() and llvm_gcda_emit_function() in the clang-11 release. Users of clang-11 or newer may have noticed their kernels failing to boot due to a panic when enabling CONFIG_GCOV_KERNEL=y +CONFIG_GCOV_PROFILE_ALL=y. Fix up the function signatures so calling these functions doesn't panic the kernel.

Link: https://reviews.llvm.org/rGcdd683b516d147925212724b09ec6fb792a40041 Link: https://reviews.llvm.org/rG13a633b438b6500ecad9e4f936ebadf3411d0f44 Cc: stable@vger.kernel.org # 5.4 Reported-by: Prasad Sodagudi psodagud@quicinc.com Suggested-by: Nathan Chancellor nathan@kernel.org Reviewed-by: Fangrui Song maskray@google.com Signed-off-by: Nick Desaulniers ndesaulniers@google.com Tested-by: Nathan Chancellor nathan@kernel.org

Reviewed-by: Nathan Chancellor nathan@kernel.org

---

Changes V1 -> V2:

• Use CONFIG_CLANG_VERSION instead of __clang_major__.
• Pick up and retain Suggested-by, Tested-by, and Reviewed-by tags.
• Drop note from commit message about `git blame`; I did what was sugguested in V1, but it still looks to git like I wrote those functions. Oh well.

kernel/gcov/clang.c | 69 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+)

diff --git a/kernel/gcov/clang.c b/kernel/gcov/clang.c index c94b820a1b62..8743150db2ac 100644 --- a/kernel/gcov/clang.c +++ b/kernel/gcov/clang.c @@ -75,7 +75,9 @@ struct gcov_fn_info { u32 num_counters; u64 *counters; +#if CONFIG_CLANG_VERSION < 110000 const char *function_name; +#endif }; static struct gcov_info *current_info; @@ -105,6 +107,7 @@ void llvm_gcov_init(llvm_gcov_callback writeout, llvm_gcov_callback flush) } EXPORT_SYMBOL(llvm_gcov_init); +#if CONFIG_CLANG_VERSION < 110000 void llvm_gcda_start_file(const char *orig_filename, const char version[4], u32 checksum) { @@ -113,7 +116,17 @@ void llvm_gcda_start_file(const char *orig_filename, const char version[4], current_info->checksum = checksum; } EXPORT_SYMBOL(llvm_gcda_start_file); +#else +void llvm_gcda_start_file(const char *orig_filename, u32 version, u32 checksum) +{

• current_info->filename = orig_filename;
• current_info->version = version;
• current_info->checksum = checksum;

+} +EXPORT_SYMBOL(llvm_gcda_start_file); +#endif +#if CONFIG_CLANG_VERSION < 110000 void llvm_gcda_emit_function(u32 ident, const char *function_name, u32 func_checksum, u8 use_extra_checksum, u32 cfg_checksum) { @@ -133,6 +146,24 @@ 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)
  

+{

• 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->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 void llvm_gcda_emit_arcs(u32 num_counters, u64 *counters) { @@ -295,6 +326,7 @@ void gcov_info_add(struct gcov_info *dst, struct gcov_info *src) } } +#if CONFIG_CLANG_VERSION < 110000 static struct gcov_fn_info *gcov_fn_info_dup(struct gcov_fn_info *fn) { size_t cv_size; /* counter values size */ @@ -322,6 +354,28 @@ static struct gcov_fn_info *gcov_fn_info_dup(struct gcov_fn_info *fn) kfree(fn_dup); return NULL; } +#else +static struct gcov_fn_info *gcov_fn_info_dup(struct gcov_fn_info *fn) +{

• size_t cv_size; /* counter values size */
• struct gcov_fn_info *fn_dup = kmemdup(fn, sizeof(*fn),

• 	GFP_KERNEL);
  

• if (!fn_dup)

• return NULL;
  

• INIT_LIST_HEAD(&fn_dup->head);
• cv_size = fn->num_counters * sizeof(fn->counters[0]);
• fn_dup->counters = vmalloc(cv_size);
• if (!fn_dup->counters) {

• kfree(fn_dup);
  

• return NULL;
  

• }
• memcpy(fn_dup->counters, fn->counters, cv_size);
• return fn_dup;

+} +#endif /**

• gcov_info_dup - duplicate profiling data set

@@ -362,6 +416,7 @@ struct gcov_info *gcov_info_dup(struct gcov_info *info)

• gcov_info_free - release memory for profiling data set duplicate
• @info: profiling data set duplicate to free

*/ +#if CONFIG_CLANG_VERSION < 110000 void gcov_info_free(struct gcov_info *info) { struct gcov_fn_info *fn, *tmp; @@ -375,6 +430,20 @@ void gcov_info_free(struct gcov_info *info) kfree(info->filename); kfree(info); } +#else +void gcov_info_free(struct gcov_info *info) +{

• struct gcov_fn_info *fn, *tmp;
• list_for_each_entry_safe(fn, tmp, &info->functions, head) {

• vfree(fn->counters);
  

• list_del(&fn->head);
  

• kfree(fn);
  

• }
• kfree(info->filename);
• kfree(info);

+} +#endif #define ITER_STRIDE PAGE_SIZE

base-commit: f78d76e72a4671ea52d12752d92077788b4f5d50

2.31.0.rc2.261.g7f71774620-goog