Messages in this thread Patch in this message | | | From | Nick Desaulniers <> | Date | Fri, 12 Mar 2021 13:57:47 -0800 | Subject | Re: [PATCH] gcov: fix clang-11+ support |
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On Fri, Mar 12, 2021 at 12:51 PM Nathan Chancellor <nathan@kernel.org> wrote: > > On Fri, Mar 12, 2021 at 12:14:42PM -0800, Nick Desaulniers wrote: > > On Fri, Mar 12, 2021 at 11:58 AM Nathan Chancellor <nathan@kernel.org> wrote: > > > > > > On Fri, Mar 12, 2021 at 11:21:39AM -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. > > > > > > > > When we drop clang-10 support from the kernel, we should carefully > > > > update the original implementations to try to preserve git blame, > > > > deleting these implementations. > > > > > > > > Link: https://reviews.llvm.org/rGcdd683b516d147925212724b09ec6fb792a40041 > > > > Link: https://reviews.llvm.org/rG13a633b438b6500ecad9e4f936ebadf3411d0f44 > > > > Cc: Fangrui Song <maskray@google.com> > > > > Reported-by: Prasad Sodagudi<psodagud@quicinc.com> > > > > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> > > > > > > I can reproduce the panic (as a boot hang) in QEMU before this patch and > > > it is resolved after it so: > > > > > > Tested-by: Nathan Chancellor <nathan@kernel.org> > > > > > > However, the duplication hurts :( would it potentially be better to just > > > do the full update to clang-11+ and require it for CONFIG_GCOV_KERNEL? > > > > > > depends on CC_IS_GCC || CLANG_VERSION >= 110000? > > > > I'm not opposed, and value your input on the matter. Either way, this > > will need to be back ported to stable. Should we be concerned with > > users of stable's branches before we mandated clang-10 as the minimum > > supported version? > > > > commit 1f7a44f63e6c ("compiler-clang: add build check for clang 10.0.1") > > > > first landed in v5.10-rc1. Does not exist in v5.4.y. The diff you > > Hmmm fair point, I did not realize that this support had landed in 5.2 > meaning that 5.4 needs it as well at 5.10. > > > suggest is certainly easier to review to observe the differences, and > > I we don't have users of the latest Android or CrOS kernels using > > older clang, but I suspect there may be older kernel versions where if > > they try to upgrade their version of clang, GCOV support will regress > > for them. Though, I guess that's fine since either approach will fix > > this for them. I guess if they don't want to upgrade from clang-10 say > > for example, then this approach can be backported to stable. > > If people are happy with this approach, it is the more "stable friendly" > change because it fixes it for all versions of clang that should have > been supported at their respective times. Maybe it is worthwhile to do > both? This change gets picked up with a Cc: stable@vger.kernel.org then > in a follow up patch, we remove the #ifdef's and gate GCOV on clang-11? > The CLANG_VERSION string is usually what we will search for when > removing old workarounds.
Sounds like we're on the same page; will send a v2 with your recommendation on top.
> Additionally, your patch could just use > > #if CLANG_VERSION <= 110000 > > to more easily see this. I have no strong opinion one way or the other > though. If people are happy with this approach, let's do it.
Err that would be nicer, but: kernel/gcov/clang.c:78:5: warning: 'CLANG_VERSION' is not defined, evaluates to 0 [-Wundef] #if CLANG_VERSION < 110000 ^ kernel/gcov/clang.c:110:5: warning: 'CLANG_VERSION' is not defined, evaluates to 0 [-Wundef] #if CLANG_VERSION < 110000 ^ kernel/gcov/clang.c:130:5: warning: 'CLANG_VERSION' is not defined, evaluates to 0 [-Wundef] #if CLANG_VERSION < 110000 ^ kernel/gcov/clang.c:330:5: warning: 'CLANG_VERSION' is not defined, evaluates to 0 [-Wundef] #if CLANG_VERSION < 110000 ^ kernel/gcov/clang.c:420:5: warning: 'CLANG_VERSION' is not defined, evaluates to 0 [-Wundef] #if CLANG_VERSION < 110000 ^
Did we just break this in commit aec6c60a01d3 ("kbuild: check the minimum compiler version in Kconfig") in v5.12-rc1? So I'll keep it as is for v2, but we should discuss with Masahiro and Miguel if we should be removing CLANG_VERSION even if there are no in tree users at the moment. (I guess I could re-introduce it in my series for v2, but that will unnecessarily complicate the backports, so I won't). My fault for not catching that in code review.
> > Cheers, > Nathan > > > > > > > > --- > > > > kernel/gcov/clang.c | 69 +++++++++++++++++++++++++++++++++++++++++++++ > > > > 1 file changed, 69 insertions(+) > > > > > > > > diff --git a/kernel/gcov/clang.c b/kernel/gcov/clang.c > > > > index c94b820a1b62..20e6760ec05d 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 __clang_major__ < 11 > > > > 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 __clang_major__ < 11 > > > > 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 __clang_major__ < 11 > > > > 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, ¤t_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, ¤t_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 __clang_major__ < 11 > > > > 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 __clang_major__ < 11 > > > > 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 > > > > > > > > > > > > -- > > Thanks, > > ~Nick Desaulniers
-- Thanks, ~Nick Desaulniers
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