| Message ID | 20221129190123.872394-2-nathan@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Herbert Xu |
| Headers | show |
| Series | Fix lack of section mismatch warnings with LTO | expand |
On Wed, Nov 30, 2022 at 4:02 AM Nathan Chancellor <nathan@kernel.org> wrote: > > When building arm64 allmodconfig + ThinLTO with clang and a proposed > modpost update to account for -ffuncton-sections, the following warning > appears: How to enable -ffuncton-sections for ARCH=arm64 ? (in other words, how to set CONFIG_LD_DEAD_CODE_DATA_ELIMINATION ?) In upstream, it is only possible for mips and powerpc. ./arch/mips/Kconfig:82: select HAVE_LD_DEAD_CODE_DATA_ELIMINATION ./arch/powerpc/Kconfig:237: select HAVE_LD_DEAD_CODE_DATA_ELIMINATION Is there another proposal to add it for arm64, or is this about a downstream kernel? > > WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text) > WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text) > > In both cases, an __init function calls padata_work_init(), which is not > marked __init, with padata_mt_helper(), another __init function, as a > work function argument. > > padata_work_init() is called from non-init paths, otherwise it could be > marked __init to resolve the warning. Instead, remove __init from > padata_mt_helper() to resolve the warning. > > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > --- > Cc: Steffen Klassert <steffen.klassert@secunet.com> > Cc: Daniel Jordan <daniel.m.jordan@oracle.com> > Cc: linux-crypto@vger.kernel.org > --- > kernel/padata.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/padata.c b/kernel/padata.c > index e5819bb8bd1d..c2271d7e446d 100644 > --- a/kernel/padata.c > +++ b/kernel/padata.c > @@ -45,7 +45,7 @@ struct padata_mt_job_state { > }; > > static void padata_free_pd(struct parallel_data *pd); > -static void __init padata_mt_helper(struct work_struct *work); > +static void padata_mt_helper(struct work_struct *work); > > static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index) > { > @@ -425,7 +425,7 @@ static int padata_setup_cpumasks(struct padata_instance *pinst) > return err; > } > > -static void __init padata_mt_helper(struct work_struct *w) > +static void padata_mt_helper(struct work_struct *w) > { > struct padata_work *pw = container_of(w, struct padata_work, pw_work); > struct padata_mt_job_state *ps = pw->pw_data; > -- > 2.38.1 >
On Wed, Nov 30, 2022 at 4:02 AM Nathan Chancellor <nathan@kernel.org> wrote: > > When building arm64 allmodconfig + ThinLTO with clang and a proposed > modpost update to account for -ffuncton-sections, the following warning > appears: > > WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text) > WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text) > > In both cases, an __init function calls padata_work_init(), which is not > marked __init, with padata_mt_helper(), another __init function, as a > work function argument. > > padata_work_init() is called from non-init paths, otherwise it could be > marked __init to resolve the warning. Instead, remove __init from > padata_mt_helper() to resolve the warning. > > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > --- > Cc: Steffen Klassert <steffen.klassert@secunet.com> > Cc: Daniel Jordan <daniel.m.jordan@oracle.com> > Cc: linux-crypto@vger.kernel.org > --- > kernel/padata.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/padata.c b/kernel/padata.c > index e5819bb8bd1d..c2271d7e446d 100644 > --- a/kernel/padata.c > +++ b/kernel/padata.c > @@ -45,7 +45,7 @@ struct padata_mt_job_state { > }; > > static void padata_free_pd(struct parallel_data *pd); > -static void __init padata_mt_helper(struct work_struct *work); > +static void padata_mt_helper(struct work_struct *work); > > static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index) > { > @@ -425,7 +425,7 @@ static int padata_setup_cpumasks(struct padata_instance *pinst) > return err; > } > > -static void __init padata_mt_helper(struct work_struct *w) > +static void padata_mt_helper(struct work_struct *w) > { > struct padata_work *pw = container_of(w, struct padata_work, pw_work); > struct padata_mt_job_state *ps = pw->pw_data; > -- > 2.38.1 > This patch seems wrong. padata_work_init() does not reference to padata_mt_helper() padata_work_alloc_mt() and padata_do_multithreaded() do.
On Thu, Dec 01, 2022 at 07:20:47AM +0900, Masahiro Yamada wrote: > On Wed, Nov 30, 2022 at 4:02 AM Nathan Chancellor <nathan@kernel.org> wrote: > > > > When building arm64 allmodconfig + ThinLTO with clang and a proposed > > modpost update to account for -ffuncton-sections, the following warning > > appears: > > > > How to enable -ffuncton-sections for ARCH=arm64 ? > (in other words, how to set CONFIG_LD_DEAD_CODE_DATA_ELIMINATION ?) clang LTO implies -fdata-sections and -ffunction-sections. $ cat foo.c int foo(void) { return 0; } $ cat bar.c extern int foo(void); int bar(void) { return foo(); } $ clang -c -o foo.{o,c} $ clang -c -o bar.{o,c} $ ld.lld -r -o foobar {foo,bar}.o $ llvm-readelf -s foobar Symbol table '.symtab' contains 9 entries: Num: Value Size Type Bind Vis Ndx Name 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND 1: 0000000000000000 0 FILE LOCAL DEFAULT ABS foo.c 2: 0000000000000000 0 SECTION LOCAL DEFAULT 1 .text 3: 0000000000000000 0 SECTION LOCAL DEFAULT 3 .eh_frame 4: 0000000000000000 0 SECTION LOCAL DEFAULT 5 .llvm_addrsig 5: 0000000000000000 0 FILE LOCAL DEFAULT ABS bar.c 6: 0000000000000000 0 SECTION LOCAL DEFAULT 2 .comment 7: 0000000000000000 8 FUNC GLOBAL DEFAULT 1 foo 8: 0000000000000010 11 FUNC GLOBAL DEFAULT 1 bar $ clang -flto -c -o foo.{o,c} $ clang -flto -c -o bar.{o,c} $ ld.lld -r -o foobar {foo,bar}.o $ llvm-readelf -s foobar Symbol table '.symtab' contains 10 entries: Num: Value Size Type Bind Vis Ndx Name 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND 1: 0000000000000000 0 FILE LOCAL DEFAULT ABS ld-temp.o 2: 0000000000000000 0 SECTION LOCAL DEFAULT 1 .text 3: 0000000000000000 0 SECTION LOCAL DEFAULT 2 .text.foo 4: 0000000000000000 0 SECTION LOCAL DEFAULT 3 .text.bar 5: 0000000000000000 0 SECTION LOCAL DEFAULT 6 .eh_frame 6: 0000000000000000 0 SECTION LOCAL DEFAULT 8 .llvm_addrsig 7: 0000000000000000 0 SECTION LOCAL DEFAULT 5 .comment 8: 0000000000000000 8 FUNC GLOBAL DEFAULT 2 foo 9: 0000000000000000 13 FUNC GLOBAL DEFAULT 3 bar > In upstream, it is only possible for mips and powerpc. > > ./arch/mips/Kconfig:82: select HAVE_LD_DEAD_CODE_DATA_ELIMINATION > ./arch/powerpc/Kconfig:237: select HAVE_LD_DEAD_CODE_DATA_ELIMINATION > > > > Is there another proposal to add it for arm64, > or is this about a downstream kernel? > > > > > > > > > WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text) > > WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text) > > > > In both cases, an __init function calls padata_work_init(), which is not > > marked __init, with padata_mt_helper(), another __init function, as a > > work function argument. > > > > padata_work_init() is called from non-init paths, otherwise it could be > > marked __init to resolve the warning. Instead, remove __init from > > padata_mt_helper() to resolve the warning. > > > > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > > --- > > Cc: Steffen Klassert <steffen.klassert@secunet.com> > > Cc: Daniel Jordan <daniel.m.jordan@oracle.com> > > Cc: linux-crypto@vger.kernel.org > > --- > > kernel/padata.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/padata.c b/kernel/padata.c > > index e5819bb8bd1d..c2271d7e446d 100644 > > --- a/kernel/padata.c > > +++ b/kernel/padata.c > > @@ -45,7 +45,7 @@ struct padata_mt_job_state { > > }; > > > > static void padata_free_pd(struct parallel_data *pd); > > -static void __init padata_mt_helper(struct work_struct *work); > > +static void padata_mt_helper(struct work_struct *work); > > > > static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index) > > { > > @@ -425,7 +425,7 @@ static int padata_setup_cpumasks(struct padata_instance *pinst) > > return err; > > } > > > > -static void __init padata_mt_helper(struct work_struct *w) > > +static void padata_mt_helper(struct work_struct *w) > > { > > struct padata_work *pw = container_of(w, struct padata_work, pw_work); > > struct padata_mt_job_state *ps = pw->pw_data; > > -- > > 2.38.1 > > > > > -- > Best Regards > Masahiro Yamada
On Thu, Dec 01, 2022 at 07:35:59AM +0900, Masahiro Yamada wrote: > On Wed, Nov 30, 2022 at 4:02 AM Nathan Chancellor <nathan@kernel.org> wrote: > > > > When building arm64 allmodconfig + ThinLTO with clang and a proposed > > modpost update to account for -ffuncton-sections, the following warning > > appears: > > > > WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text) > > WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text) > > > > In both cases, an __init function calls padata_work_init(), which is not > > marked __init, with padata_mt_helper(), another __init function, as a > > work function argument. > > > > padata_work_init() is called from non-init paths, otherwise it could be > > marked __init to resolve the warning. Instead, remove __init from > > padata_mt_helper() to resolve the warning. > > > > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > > --- > > Cc: Steffen Klassert <steffen.klassert@secunet.com> > > Cc: Daniel Jordan <daniel.m.jordan@oracle.com> > > Cc: linux-crypto@vger.kernel.org > > --- > > kernel/padata.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/padata.c b/kernel/padata.c > > index e5819bb8bd1d..c2271d7e446d 100644 > > --- a/kernel/padata.c > > +++ b/kernel/padata.c > > @@ -45,7 +45,7 @@ struct padata_mt_job_state { > > }; > > > > static void padata_free_pd(struct parallel_data *pd); > > -static void __init padata_mt_helper(struct work_struct *work); > > +static void padata_mt_helper(struct work_struct *work); > > > > static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index) > > { > > @@ -425,7 +425,7 @@ static int padata_setup_cpumasks(struct padata_instance *pinst) > > return err; > > } > > > > -static void __init padata_mt_helper(struct work_struct *w) > > +static void padata_mt_helper(struct work_struct *w) > > { > > struct padata_work *pw = container_of(w, struct padata_work, pw_work); > > struct padata_mt_job_state *ps = pw->pw_data; > > -- > > 2.38.1 > > > > This patch seems wrong. > > padata_work_init() does not reference to padata_mt_helper() > > > padata_work_alloc_mt() and padata_do_multithreaded() do. I see LLVM optimizing padata_work_init by embedding padata_mt_helper's address in its text, which runs afoul of modpost. I agree with Masahiro, the warning is a false positive since only __init functions ever cause the embedded address to be used. We have __ref for situations like this. That way, padata_mt_helper can stay properly __init.
On Tue, Dec 06, 2022 at 03:15:26PM -0500, Daniel Jordan wrote: > On Thu, Dec 01, 2022 at 07:35:59AM +0900, Masahiro Yamada wrote: > > On Wed, Nov 30, 2022 at 4:02 AM Nathan Chancellor <nathan@kernel.org> wrote: > > > > > > When building arm64 allmodconfig + ThinLTO with clang and a proposed > > > modpost update to account for -ffuncton-sections, the following warning > > > appears: > > > > > > WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text) > > > WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text) > > > > > > In both cases, an __init function calls padata_work_init(), which is not > > > marked __init, with padata_mt_helper(), another __init function, as a > > > work function argument. > > > > > > padata_work_init() is called from non-init paths, otherwise it could be > > > marked __init to resolve the warning. Instead, remove __init from > > > padata_mt_helper() to resolve the warning. > > > > > > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > > > --- > > > Cc: Steffen Klassert <steffen.klassert@secunet.com> > > > Cc: Daniel Jordan <daniel.m.jordan@oracle.com> > > > Cc: linux-crypto@vger.kernel.org > > > --- > > > kernel/padata.c | 4 ++-- > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/kernel/padata.c b/kernel/padata.c > > > index e5819bb8bd1d..c2271d7e446d 100644 > > > --- a/kernel/padata.c > > > +++ b/kernel/padata.c > > > @@ -45,7 +45,7 @@ struct padata_mt_job_state { > > > }; > > > > > > static void padata_free_pd(struct parallel_data *pd); > > > -static void __init padata_mt_helper(struct work_struct *work); > > > +static void padata_mt_helper(struct work_struct *work); > > > > > > static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index) > > > { > > > @@ -425,7 +425,7 @@ static int padata_setup_cpumasks(struct padata_instance *pinst) > > > return err; > > > } > > > > > > -static void __init padata_mt_helper(struct work_struct *w) > > > +static void padata_mt_helper(struct work_struct *w) > > > { > > > struct padata_work *pw = container_of(w, struct padata_work, pw_work); > > > struct padata_mt_job_state *ps = pw->pw_data; > > > -- > > > 2.38.1 > > > > > > > This patch seems wrong. > > > > padata_work_init() does not reference to padata_mt_helper() > > > > > > padata_work_alloc_mt() and padata_do_multithreaded() do. > > I see LLVM optimizing padata_work_init by embedding padata_mt_helper's > address in its text, which runs afoul of modpost. > > I agree with Masahiro, the warning is a false positive since only __init > functions ever cause the embedded address to be used. > > We have __ref for situations like this. That way, padata_mt_helper can > stay properly __init. Ah, thank you for pointing out __ref, that seems to be exactly what we want here. I will send a v2 marking padata_work_init() as __ref shortly. Cheers, Nathan
diff --git a/kernel/padata.c b/kernel/padata.c index e5819bb8bd1d..c2271d7e446d 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -45,7 +45,7 @@ struct padata_mt_job_state { }; static void padata_free_pd(struct parallel_data *pd); -static void __init padata_mt_helper(struct work_struct *work); +static void padata_mt_helper(struct work_struct *work); static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index) { @@ -425,7 +425,7 @@ static int padata_setup_cpumasks(struct padata_instance *pinst) return err; } -static void __init padata_mt_helper(struct work_struct *w) +static void padata_mt_helper(struct work_struct *w) { struct padata_work *pw = container_of(w, struct padata_work, pw_work); struct padata_mt_job_state *ps = pw->pw_data;
When building arm64 allmodconfig + ThinLTO with clang and a proposed modpost update to account for -ffuncton-sections, the following warning appears: WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text) WARNING: modpost: vmlinux.o: section mismatch in reference: padata_work_init (section: .text.padata_work_init) -> padata_mt_helper (section: .init.text) In both cases, an __init function calls padata_work_init(), which is not marked __init, with padata_mt_helper(), another __init function, as a work function argument. padata_work_init() is called from non-init paths, otherwise it could be marked __init to resolve the warning. Instead, remove __init from padata_mt_helper() to resolve the warning. Signed-off-by: Nathan Chancellor <nathan@kernel.org> --- Cc: Steffen Klassert <steffen.klassert@secunet.com> Cc: Daniel Jordan <daniel.m.jordan@oracle.com> Cc: linux-crypto@vger.kernel.org --- kernel/padata.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)