| Message ID | 20240415075837.2349766-8-ardb+git@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | kbuild: Avoid weak external linkage where possible | expand |
On Mon, Apr 15, 2024 at 09:58:41AM +0200, Ard Biesheuvel wrote: > From: Ard Biesheuvel <ardb@kernel.org> > > If the BTF code is enabled in the build configuration, the start/stop > BTF markers are guaranteed to exist in the final link but not during the > first linker pass. > > Avoid GOT based relocations to these markers in the final executable by > providing preliminary definitions that will be used by the first linker > pass, and superseded by the actual definitions in the subsequent ones. > > Make the preliminary definitions dependent on CONFIG_DEBUG_INFO_BTF so > that inadvertent references to this section will trigger a link failure > if they occur in code that does not honour CONFIG_DEBUG_INFO_BTF. > > Note that Clang will notice that taking the address of__start_BTF cannot > yield NULL any longer, so testing for that condition is no longer > needed. > > Acked-by: Andrii Nakryiko <andrii@kernel.org> > Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Jiri Olsa <jolsa@kernel.org> jirka > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > --- > include/asm-generic/vmlinux.lds.h | 9 +++++++++ > kernel/bpf/btf.c | 7 +++++-- > kernel/bpf/sysfs_btf.c | 6 +++--- > 3 files changed, 17 insertions(+), 5 deletions(-) > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index e8449be62058..4cb3d88449e5 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -456,6 +456,7 @@ > * independent code. > */ > #define PRELIMINARY_SYMBOL_DEFINITIONS \ > + PRELIMINARY_BTF_DEFINITIONS \ > PROVIDE(kallsyms_addresses = .); \ > PROVIDE(kallsyms_offsets = .); \ > PROVIDE(kallsyms_names = .); \ > @@ -466,6 +467,14 @@ > PROVIDE(kallsyms_markers = .); \ > PROVIDE(kallsyms_seqs_of_names = .); > > +#ifdef CONFIG_DEBUG_INFO_BTF > +#define PRELIMINARY_BTF_DEFINITIONS \ > + PROVIDE(__start_BTF = .); \ > + PROVIDE(__stop_BTF = .); > +#else > +#define PRELIMINARY_BTF_DEFINITIONS > +#endif > + > /* > * Read only Data > */ > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c > index 90c4a32d89ff..6d46cee47ae3 100644 > --- a/kernel/bpf/btf.c > +++ b/kernel/bpf/btf.c > @@ -5642,8 +5642,8 @@ static struct btf *btf_parse(const union bpf_attr *attr, bpfptr_t uattr, u32 uat > return ERR_PTR(err); > } > > -extern char __weak __start_BTF[]; > -extern char __weak __stop_BTF[]; > +extern char __start_BTF[]; > +extern char __stop_BTF[]; > extern struct btf *btf_vmlinux; > > #define BPF_MAP_TYPE(_id, _ops) > @@ -5971,6 +5971,9 @@ struct btf *btf_parse_vmlinux(void) > struct btf *btf = NULL; > int err; > > + if (!IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) > + return ERR_PTR(-ENOENT); > + > env = kzalloc(sizeof(*env), GFP_KERNEL | __GFP_NOWARN); > if (!env) > return ERR_PTR(-ENOMEM); > diff --git a/kernel/bpf/sysfs_btf.c b/kernel/bpf/sysfs_btf.c > index ef6911aee3bb..fedb54c94cdb 100644 > --- a/kernel/bpf/sysfs_btf.c > +++ b/kernel/bpf/sysfs_btf.c > @@ -9,8 +9,8 @@ > #include <linux/sysfs.h> > > /* See scripts/link-vmlinux.sh, gen_btf() func for details */ > -extern char __weak __start_BTF[]; > -extern char __weak __stop_BTF[]; > +extern char __start_BTF[]; > +extern char __stop_BTF[]; > > static ssize_t > btf_vmlinux_read(struct file *file, struct kobject *kobj, > @@ -32,7 +32,7 @@ static int __init btf_vmlinux_init(void) > { > bin_attr_btf_vmlinux.size = __stop_BTF - __start_BTF; > > - if (!__start_BTF || bin_attr_btf_vmlinux.size == 0) > + if (bin_attr_btf_vmlinux.size == 0) > return 0; > > btf_kobj = kobject_create_and_add("btf", kernel_kobj); > -- > 2.44.0.683.g7961c838ac-goog >
On Mon, Apr 15, 2024 at 4:58 PM Ard Biesheuvel <ardb+git@google.com> wrote: > > From: Ard Biesheuvel <ardb@kernel.org> > > If the BTF code is enabled in the build configuration, the start/stop > BTF markers are guaranteed to exist in the final link but not during the > first linker pass. > > Avoid GOT based relocations to these markers in the final executable by > providing preliminary definitions that will be used by the first linker > pass, and superseded by the actual definitions in the subsequent ones. > > Make the preliminary definitions dependent on CONFIG_DEBUG_INFO_BTF so > that inadvertent references to this section will trigger a link failure > if they occur in code that does not honour CONFIG_DEBUG_INFO_BTF. > > Note that Clang will notice that taking the address of__start_BTF cannot > yield NULL any longer, so testing for that condition is no longer > needed. > > Acked-by: Andrii Nakryiko <andrii@kernel.org> > Acked-by: Arnd Bergmann <arnd@arndb.de> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > --- > include/asm-generic/vmlinux.lds.h | 9 +++++++++ > kernel/bpf/btf.c | 7 +++++-- > kernel/bpf/sysfs_btf.c | 6 +++--- > 3 files changed, 17 insertions(+), 5 deletions(-) > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index e8449be62058..4cb3d88449e5 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -456,6 +456,7 @@ > * independent code. > */ > #define PRELIMINARY_SYMBOL_DEFINITIONS \ > + PRELIMINARY_BTF_DEFINITIONS \ > PROVIDE(kallsyms_addresses = .); \ > PROVIDE(kallsyms_offsets = .); \ > PROVIDE(kallsyms_names = .); \ > @@ -466,6 +467,14 @@ > PROVIDE(kallsyms_markers = .); \ > PROVIDE(kallsyms_seqs_of_names = .); > > +#ifdef CONFIG_DEBUG_INFO_BTF > +#define PRELIMINARY_BTF_DEFINITIONS \ > + PROVIDE(__start_BTF = .); \ > + PROVIDE(__stop_BTF = .); > +#else > +#define PRELIMINARY_BTF_DEFINITIONS > +#endif > + Is this necessary? The following code (BOUNDED_SECTION_BY) produces __start_BTF and __stop_BTF symbols under the same condition. /* * .BTF */ #ifdef CONFIG_DEBUG_INFO_BTF #define BTF \ .BTF : AT(ADDR(.BTF) - LOAD_OFFSET) { \ BOUNDED_SECTION_BY(.BTF, _BTF) \ } \ . = ALIGN(4); \ .BTF_ids : AT(ADDR(.BTF_ids) - LOAD_OFFSET) { \ *(.BTF_ids) \ } #else #define BTF #endif > /* > * Read only Data > */ > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c > index 90c4a32d89ff..6d46cee47ae3 100644 > --- a/kernel/bpf/btf.c > +++ b/kernel/bpf/btf.c > @@ -5642,8 +5642,8 @@ static struct btf *btf_parse(const union bpf_attr *attr, bpfptr_t uattr, u32 uat > return ERR_PTR(err); > } > > -extern char __weak __start_BTF[]; > -extern char __weak __stop_BTF[]; > +extern char __start_BTF[]; > +extern char __stop_BTF[]; > extern struct btf *btf_vmlinux; > > #define BPF_MAP_TYPE(_id, _ops) > @@ -5971,6 +5971,9 @@ struct btf *btf_parse_vmlinux(void) > struct btf *btf = NULL; > int err; > > + if (!IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) > + return ERR_PTR(-ENOENT); > + > env = kzalloc(sizeof(*env), GFP_KERNEL | __GFP_NOWARN); > if (!env) > return ERR_PTR(-ENOMEM); > diff --git a/kernel/bpf/sysfs_btf.c b/kernel/bpf/sysfs_btf.c > index ef6911aee3bb..fedb54c94cdb 100644 > --- a/kernel/bpf/sysfs_btf.c > +++ b/kernel/bpf/sysfs_btf.c > @@ -9,8 +9,8 @@ > #include <linux/sysfs.h> > > /* See scripts/link-vmlinux.sh, gen_btf() func for details */ > -extern char __weak __start_BTF[]; > -extern char __weak __stop_BTF[]; > +extern char __start_BTF[]; > +extern char __stop_BTF[]; > > static ssize_t > btf_vmlinux_read(struct file *file, struct kobject *kobj, > @@ -32,7 +32,7 @@ static int __init btf_vmlinux_init(void) > { > bin_attr_btf_vmlinux.size = __stop_BTF - __start_BTF; > > - if (!__start_BTF || bin_attr_btf_vmlinux.size == 0) > + if (bin_attr_btf_vmlinux.size == 0) > return 0; > > btf_kobj = kobject_create_and_add("btf", kernel_kobj); > -- > 2.44.0.683.g7961c838ac-goog >
On Mon, 15 Apr 2024 at 16:55, Masahiro Yamada <masahiroy@kernel.org> wrote: > > On Mon, Apr 15, 2024 at 4:58 PM Ard Biesheuvel <ardb+git@google.com> wrote: > > > > From: Ard Biesheuvel <ardb@kernel.org> > > > > If the BTF code is enabled in the build configuration, the start/stop > > BTF markers are guaranteed to exist in the final link but not during the > > first linker pass. > > > > Avoid GOT based relocations to these markers in the final executable by > > providing preliminary definitions that will be used by the first linker > > pass, and superseded by the actual definitions in the subsequent ones. > > > > Make the preliminary definitions dependent on CONFIG_DEBUG_INFO_BTF so > > that inadvertent references to this section will trigger a link failure > > if they occur in code that does not honour CONFIG_DEBUG_INFO_BTF. > > > > Note that Clang will notice that taking the address of__start_BTF cannot > > yield NULL any longer, so testing for that condition is no longer > > needed. > > > > Acked-by: Andrii Nakryiko <andrii@kernel.org> > > Acked-by: Arnd Bergmann <arnd@arndb.de> > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > > --- > > include/asm-generic/vmlinux.lds.h | 9 +++++++++ > > kernel/bpf/btf.c | 7 +++++-- > > kernel/bpf/sysfs_btf.c | 6 +++--- > > 3 files changed, 17 insertions(+), 5 deletions(-) > > > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > > index e8449be62058..4cb3d88449e5 100644 > > --- a/include/asm-generic/vmlinux.lds.h > > +++ b/include/asm-generic/vmlinux.lds.h > > @@ -456,6 +456,7 @@ > > * independent code. > > */ > > #define PRELIMINARY_SYMBOL_DEFINITIONS \ > > + PRELIMINARY_BTF_DEFINITIONS \ > > PROVIDE(kallsyms_addresses = .); \ > > PROVIDE(kallsyms_offsets = .); \ > > PROVIDE(kallsyms_names = .); \ > > @@ -466,6 +467,14 @@ > > PROVIDE(kallsyms_markers = .); \ > > PROVIDE(kallsyms_seqs_of_names = .); > > > > +#ifdef CONFIG_DEBUG_INFO_BTF > > +#define PRELIMINARY_BTF_DEFINITIONS \ > > + PROVIDE(__start_BTF = .); \ > > + PROVIDE(__stop_BTF = .); > > +#else > > +#define PRELIMINARY_BTF_DEFINITIONS > > +#endif > > + > > > > Is this necessary? > I think so. This actually resulted in Jiri's build failure with v2, and the realization that there was dead code in btf_parse_vmlinux() that happily tried to load the contents of the BTF section if CONFIG_DEBUG_INFO_BTF was not enabled to begin with. So this is another pitfall with weak references: the symbol may unexpectedly be missing altogether rather than only during the first linker pass. > > > The following code (BOUNDED_SECTION_BY) > produces __start_BTF and __stop_BTF symbols > under the same condition. > Indeed. So if CONFIG_DEBUG_INFO_BTF=n, code can still link to __start_BTF and __stop_BTF even though BTF is not enabled. > > > /* > * .BTF > */ > #ifdef CONFIG_DEBUG_INFO_BTF > #define BTF \ > .BTF : AT(ADDR(.BTF) - LOAD_OFFSET) { \ > BOUNDED_SECTION_BY(.BTF, _BTF) \ > } \ > . = ALIGN(4); \ > .BTF_ids : AT(ADDR(.BTF_ids) - LOAD_OFFSET) { \ > *(.BTF_ids) \ > } > #else > #define BTF > #endif > > > > > > > > > > > > > /* > > * Read only Data > > */ > > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c > > index 90c4a32d89ff..6d46cee47ae3 100644 > > --- a/kernel/bpf/btf.c > > +++ b/kernel/bpf/btf.c > > @@ -5642,8 +5642,8 @@ static struct btf *btf_parse(const union bpf_attr *attr, bpfptr_t uattr, u32 uat > > return ERR_PTR(err); > > } > > > > -extern char __weak __start_BTF[]; > > -extern char __weak __stop_BTF[]; > > +extern char __start_BTF[]; > > +extern char __stop_BTF[]; > > extern struct btf *btf_vmlinux; > > > > #define BPF_MAP_TYPE(_id, _ops) > > @@ -5971,6 +5971,9 @@ struct btf *btf_parse_vmlinux(void) > > struct btf *btf = NULL; > > int err; > > > > + if (!IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) > > + return ERR_PTR(-ENOENT); > > + > > env = kzalloc(sizeof(*env), GFP_KERNEL | __GFP_NOWARN); > > if (!env) > > return ERR_PTR(-ENOMEM); > > diff --git a/kernel/bpf/sysfs_btf.c b/kernel/bpf/sysfs_btf.c > > index ef6911aee3bb..fedb54c94cdb 100644 > > --- a/kernel/bpf/sysfs_btf.c > > +++ b/kernel/bpf/sysfs_btf.c > > @@ -9,8 +9,8 @@ > > #include <linux/sysfs.h> > > > > /* See scripts/link-vmlinux.sh, gen_btf() func for details */ > > -extern char __weak __start_BTF[]; > > -extern char __weak __stop_BTF[]; > > +extern char __start_BTF[]; > > +extern char __stop_BTF[]; > > > > static ssize_t > > btf_vmlinux_read(struct file *file, struct kobject *kobj, > > @@ -32,7 +32,7 @@ static int __init btf_vmlinux_init(void) > > { > > bin_attr_btf_vmlinux.size = __stop_BTF - __start_BTF; > > > > - if (!__start_BTF || bin_attr_btf_vmlinux.size == 0) > > + if (bin_attr_btf_vmlinux.size == 0) > > return 0; > > > > btf_kobj = kobject_create_and_add("btf", kernel_kobj); > > -- > > 2.44.0.683.g7961c838ac-goog > > > > > -- > Best Regards > Masahiro Yamada
On Mon, Apr 15, 2024 at 11:59 PM Ard Biesheuvel <ardb@kernel.org> wrote: > > On Mon, 15 Apr 2024 at 16:55, Masahiro Yamada <masahiroy@kernel.org> wrote: > > > > On Mon, Apr 15, 2024 at 4:58 PM Ard Biesheuvel <ardb+git@google.com> wrote: > > > > > > From: Ard Biesheuvel <ardb@kernel.org> > > > > > > If the BTF code is enabled in the build configuration, the start/stop > > > BTF markers are guaranteed to exist in the final link but not during the > > > first linker pass. > > > > > > Avoid GOT based relocations to these markers in the final executable by > > > providing preliminary definitions that will be used by the first linker > > > pass, and superseded by the actual definitions in the subsequent ones. > > > > > > Make the preliminary definitions dependent on CONFIG_DEBUG_INFO_BTF so > > > that inadvertent references to this section will trigger a link failure > > > if they occur in code that does not honour CONFIG_DEBUG_INFO_BTF. > > > > > > Note that Clang will notice that taking the address of__start_BTF cannot > > > yield NULL any longer, so testing for that condition is no longer > > > needed. > > > > > > Acked-by: Andrii Nakryiko <andrii@kernel.org> > > > Acked-by: Arnd Bergmann <arnd@arndb.de> > > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > > > --- > > > include/asm-generic/vmlinux.lds.h | 9 +++++++++ > > > kernel/bpf/btf.c | 7 +++++-- > > > kernel/bpf/sysfs_btf.c | 6 +++--- > > > 3 files changed, 17 insertions(+), 5 deletions(-) > > > > > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > > > index e8449be62058..4cb3d88449e5 100644 > > > --- a/include/asm-generic/vmlinux.lds.h > > > +++ b/include/asm-generic/vmlinux.lds.h > > > @@ -456,6 +456,7 @@ > > > * independent code. > > > */ > > > #define PRELIMINARY_SYMBOL_DEFINITIONS \ > > > + PRELIMINARY_BTF_DEFINITIONS \ > > > PROVIDE(kallsyms_addresses = .); \ > > > PROVIDE(kallsyms_offsets = .); \ > > > PROVIDE(kallsyms_names = .); \ > > > @@ -466,6 +467,14 @@ > > > PROVIDE(kallsyms_markers = .); \ > > > PROVIDE(kallsyms_seqs_of_names = .); > > > > > > +#ifdef CONFIG_DEBUG_INFO_BTF > > > +#define PRELIMINARY_BTF_DEFINITIONS \ > > > + PROVIDE(__start_BTF = .); \ > > > + PROVIDE(__stop_BTF = .); > > > +#else > > > +#define PRELIMINARY_BTF_DEFINITIONS > > > +#endif > > > + > > > > > > > > Is this necessary? > > > > I think so. > > This actually resulted in Jiri's build failure with v2, and the > realization that there was dead code in btf_parse_vmlinux() that > happily tried to load the contents of the BTF section if > CONFIG_DEBUG_INFO_BTF was not enabled to begin with. > > So this is another pitfall with weak references: the symbol may > unexpectedly be missing altogether rather than only during the first > linker pass. > > > > > > > The following code (BOUNDED_SECTION_BY) > > produces __start_BTF and __stop_BTF symbols > > under the same condition. > > > > Indeed. So if CONFIG_DEBUG_INFO_BTF=n, code can still link to > __start_BTF and __stop_BTF even though BTF is not enabled. I am talking about the case for CONFIG_DEBUG_INFO_BTF=y. PROVIDE() is meaningless because __start_BTF and __stop_BTF are produced by the existing code. (The code was a bit clearer before commit 9b351be25360c5cedfb98b88d6dfd89327849e52) So, v4 of this patch will look like 2/3, right? Just drop __weak attribute. You still need if (!IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) return ERR_PTR(-ENOENT); But, you do not need to modify vmlinux.lds.h -- Best Regards Masahiro Yamada
On Mon, 15 Apr 2024 at 17:32, Masahiro Yamada <masahiroy@kernel.org> wrote: > > On Mon, Apr 15, 2024 at 11:59 PM Ard Biesheuvel <ardb@kernel.org> wrote: > > > > On Mon, 15 Apr 2024 at 16:55, Masahiro Yamada <masahiroy@kernel.org> wrote: > > > > > > On Mon, Apr 15, 2024 at 4:58 PM Ard Biesheuvel <ardb+git@google.com> wrote: > > > > > > > > From: Ard Biesheuvel <ardb@kernel.org> > > > > > > > > If the BTF code is enabled in the build configuration, the start/stop > > > > BTF markers are guaranteed to exist in the final link but not during the > > > > first linker pass. > > > > > > > > Avoid GOT based relocations to these markers in the final executable by > > > > providing preliminary definitions that will be used by the first linker > > > > pass, and superseded by the actual definitions in the subsequent ones. > > > > > > > > Make the preliminary definitions dependent on CONFIG_DEBUG_INFO_BTF so > > > > that inadvertent references to this section will trigger a link failure > > > > if they occur in code that does not honour CONFIG_DEBUG_INFO_BTF. > > > > > > > > Note that Clang will notice that taking the address of__start_BTF cannot > > > > yield NULL any longer, so testing for that condition is no longer > > > > needed. > > > > > > > > Acked-by: Andrii Nakryiko <andrii@kernel.org> > > > > Acked-by: Arnd Bergmann <arnd@arndb.de> > > > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > > > > --- > > > > include/asm-generic/vmlinux.lds.h | 9 +++++++++ > > > > kernel/bpf/btf.c | 7 +++++-- > > > > kernel/bpf/sysfs_btf.c | 6 +++--- > > > > 3 files changed, 17 insertions(+), 5 deletions(-) > > > > > > > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > > > > index e8449be62058..4cb3d88449e5 100644 > > > > --- a/include/asm-generic/vmlinux.lds.h > > > > +++ b/include/asm-generic/vmlinux.lds.h > > > > @@ -456,6 +456,7 @@ > > > > * independent code. > > > > */ > > > > #define PRELIMINARY_SYMBOL_DEFINITIONS \ > > > > + PRELIMINARY_BTF_DEFINITIONS \ > > > > PROVIDE(kallsyms_addresses = .); \ > > > > PROVIDE(kallsyms_offsets = .); \ > > > > PROVIDE(kallsyms_names = .); \ > > > > @@ -466,6 +467,14 @@ > > > > PROVIDE(kallsyms_markers = .); \ > > > > PROVIDE(kallsyms_seqs_of_names = .); > > > > > > > > +#ifdef CONFIG_DEBUG_INFO_BTF > > > > +#define PRELIMINARY_BTF_DEFINITIONS \ > > > > + PROVIDE(__start_BTF = .); \ > > > > + PROVIDE(__stop_BTF = .); > > > > +#else > > > > +#define PRELIMINARY_BTF_DEFINITIONS > > > > +#endif > > > > + > > > > > > > > > > > > Is this necessary? > > > > > > > I think so. > > > > This actually resulted in Jiri's build failure with v2, and the > > realization that there was dead code in btf_parse_vmlinux() that > > happily tried to load the contents of the BTF section if > > CONFIG_DEBUG_INFO_BTF was not enabled to begin with. > > > > So this is another pitfall with weak references: the symbol may > > unexpectedly be missing altogether rather than only during the first > > linker pass. > > > > > > > > > > > The following code (BOUNDED_SECTION_BY) > > > produces __start_BTF and __stop_BTF symbols > > > under the same condition. > > > > > > > Indeed. So if CONFIG_DEBUG_INFO_BTF=n, code can still link to > > __start_BTF and __stop_BTF even though BTF is not enabled. > > > > I am talking about the case for CONFIG_DEBUG_INFO_BTF=y. > > PROVIDE() is meaningless because __start_BTF and __stop_BTF > are produced by the existing code. > > (The code was a bit clearer before commit > 9b351be25360c5cedfb98b88d6dfd89327849e52) > > > > So, v4 of this patch will look like 2/3, right? > > > Just drop __weak attribute. > > You still need > > if (!IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) > return ERR_PTR(-ENOENT); > > But, you do not need to modify vmlinux.lds.h > OK, I see what you mean now. The PROVIDE() is indeed unnecessary - I'll drop that bit in v4.
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index e8449be62058..4cb3d88449e5 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -456,6 +456,7 @@ * independent code. */ #define PRELIMINARY_SYMBOL_DEFINITIONS \ + PRELIMINARY_BTF_DEFINITIONS \ PROVIDE(kallsyms_addresses = .); \ PROVIDE(kallsyms_offsets = .); \ PROVIDE(kallsyms_names = .); \ @@ -466,6 +467,14 @@ PROVIDE(kallsyms_markers = .); \ PROVIDE(kallsyms_seqs_of_names = .); +#ifdef CONFIG_DEBUG_INFO_BTF +#define PRELIMINARY_BTF_DEFINITIONS \ + PROVIDE(__start_BTF = .); \ + PROVIDE(__stop_BTF = .); +#else +#define PRELIMINARY_BTF_DEFINITIONS +#endif + /* * Read only Data */ diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 90c4a32d89ff..6d46cee47ae3 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -5642,8 +5642,8 @@ static struct btf *btf_parse(const union bpf_attr *attr, bpfptr_t uattr, u32 uat return ERR_PTR(err); } -extern char __weak __start_BTF[]; -extern char __weak __stop_BTF[]; +extern char __start_BTF[]; +extern char __stop_BTF[]; extern struct btf *btf_vmlinux; #define BPF_MAP_TYPE(_id, _ops) @@ -5971,6 +5971,9 @@ struct btf *btf_parse_vmlinux(void) struct btf *btf = NULL; int err; + if (!IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) + return ERR_PTR(-ENOENT); + env = kzalloc(sizeof(*env), GFP_KERNEL | __GFP_NOWARN); if (!env) return ERR_PTR(-ENOMEM); diff --git a/kernel/bpf/sysfs_btf.c b/kernel/bpf/sysfs_btf.c index ef6911aee3bb..fedb54c94cdb 100644 --- a/kernel/bpf/sysfs_btf.c +++ b/kernel/bpf/sysfs_btf.c @@ -9,8 +9,8 @@ #include <linux/sysfs.h> /* See scripts/link-vmlinux.sh, gen_btf() func for details */ -extern char __weak __start_BTF[]; -extern char __weak __stop_BTF[]; +extern char __start_BTF[]; +extern char __stop_BTF[]; static ssize_t btf_vmlinux_read(struct file *file, struct kobject *kobj, @@ -32,7 +32,7 @@ static int __init btf_vmlinux_init(void) { bin_attr_btf_vmlinux.size = __stop_BTF - __start_BTF; - if (!__start_BTF || bin_attr_btf_vmlinux.size == 0) + if (bin_attr_btf_vmlinux.size == 0) return 0; btf_kobj = kobject_create_and_add("btf", kernel_kobj);