Allow properly marked bpf programs to call crash_kexec().
Signed-off-by: Artem Savkov <[email protected]>
---
kernel/kexec_core.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 4d34c78334ce..9259ea3bd693 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -39,6 +39,8 @@
#include <linux/hugetlb.h>
#include <linux/objtool.h>
#include <linux/kmsg_dump.h>
+#include <linux/btf.h>
+#include <linux/btf_ids.h>
#include <asm/page.h>
#include <asm/sections.h>
@@ -1238,3 +1240,22 @@ void __weak arch_kexec_protect_crashkres(void)
void __weak arch_kexec_unprotect_crashkres(void)
{}
+
+#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+BTF_SET8_START(kexec_btf_ids)
+BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
+BTF_SET8_END(kexec_btf_ids)
+
+static const struct btf_kfunc_id_set kexec_kfunc_set = {
+ .owner = THIS_MODULE,
+ .set = &kexec_btf_ids,
+};
+
+static int __init crash_kfunc_init(void)
+{
+ register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &kexec_kfunc_set);
+ return 0;
+}
+
+subsys_initcall(crash_kfunc_init);
+#endif
--
2.35.3
On Tue, Aug 02, 2022 at 11:10:29AM +0200, Artem Savkov wrote:
> Allow properly marked bpf programs to call crash_kexec().
>
> Signed-off-by: Artem Savkov <[email protected]>
> ---
> kernel/kexec_core.c | 21 +++++++++++++++++++++
> 1 file changed, 21 insertions(+)
>
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 4d34c78334ce..9259ea3bd693 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -39,6 +39,8 @@
> #include <linux/hugetlb.h>
> #include <linux/objtool.h>
> #include <linux/kmsg_dump.h>
> +#include <linux/btf.h>
> +#include <linux/btf_ids.h>
>
> #include <asm/page.h>
> #include <asm/sections.h>
> @@ -1238,3 +1240,22 @@ void __weak arch_kexec_protect_crashkres(void)
>
> void __weak arch_kexec_unprotect_crashkres(void)
> {}
> +
> +#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
> +BTF_SET8_START(kexec_btf_ids)
> +BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
> +BTF_SET8_END(kexec_btf_ids)
> +
> +static const struct btf_kfunc_id_set kexec_kfunc_set = {
> + .owner = THIS_MODULE,
> + .set = &kexec_btf_ids,
> +};
> +
> +static int __init crash_kfunc_init(void)
> +{
> + register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &kexec_kfunc_set);
> + return 0;
should we do 'return register_btf_kfunc_id_set(...' in here?
jirka
> +}
> +
> +subsys_initcall(crash_kfunc_init);
> +#endif
> --
> 2.35.3
>
On Tue, Aug 02, 2022 at 12:46:42PM +0200, Jiri Olsa wrote:
> On Tue, Aug 02, 2022 at 11:10:29AM +0200, Artem Savkov wrote:
> > +static int __init crash_kfunc_init(void)
> > +{
> > + register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &kexec_kfunc_set);
> > + return 0;
>
> should we do 'return register_btf_kfunc_id_set(...' in here?
Maybe, but as far as I can tell the return value for init calls does
absolutely nothing except for showing up in a debug message. So I don't
think it will be worth a respin, but if there is one anyway I'll change
this.
--
Artem
On Tue, Aug 2, 2022 at 2:10 AM Artem Savkov <[email protected]> wrote:
>
> Allow properly marked bpf programs to call crash_kexec().
>
> Signed-off-by: Artem Savkov <[email protected]>
> ---
> kernel/kexec_core.c | 21 +++++++++++++++++++++
> 1 file changed, 21 insertions(+)
>
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 4d34c78334ce..9259ea3bd693 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -39,6 +39,8 @@
> #include <linux/hugetlb.h>
> #include <linux/objtool.h>
> #include <linux/kmsg_dump.h>
> +#include <linux/btf.h>
> +#include <linux/btf_ids.h>
>
> #include <asm/page.h>
> #include <asm/sections.h>
> @@ -1238,3 +1240,22 @@ void __weak arch_kexec_protect_crashkres(void)
>
> void __weak arch_kexec_unprotect_crashkres(void)
> {}
> +
> +#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
> +BTF_SET8_START(kexec_btf_ids)
> +BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
> +BTF_SET8_END(kexec_btf_ids)
> +
> +static const struct btf_kfunc_id_set kexec_kfunc_set = {
> + .owner = THIS_MODULE,
> + .set = &kexec_btf_ids,
> +};
> +
> +static int __init crash_kfunc_init(void)
> +{
> + register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &kexec_kfunc_set);
> + return 0;
> +}
> +
> +subsys_initcall(crash_kfunc_init);
> +#endif
It feels there will be a bunch of such boiler plate code
in different .c files in many places in the kernel
if we go with this approach.
Maybe we should do one call:
register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING
from kernel/bpf/helper.c
to register all tracing kfuncs ?
And gate
BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
with #ifdef CONFIG_KEXEC_CORE.
We have such a pattern in verifier.c already.
On Thu, Aug 04, 2022 at 01:41:53PM -0700, Alexei Starovoitov wrote:
> On Tue, Aug 2, 2022 at 2:10 AM Artem Savkov <[email protected]> wrote:
> >
> > Allow properly marked bpf programs to call crash_kexec().
> >
> > Signed-off-by: Artem Savkov <[email protected]>
> > ---
> > kernel/kexec_core.c | 21 +++++++++++++++++++++
> > 1 file changed, 21 insertions(+)
> >
> > diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> > index 4d34c78334ce..9259ea3bd693 100644
> > --- a/kernel/kexec_core.c
> > +++ b/kernel/kexec_core.c
> > @@ -39,6 +39,8 @@
> > #include <linux/hugetlb.h>
> > #include <linux/objtool.h>
> > #include <linux/kmsg_dump.h>
> > +#include <linux/btf.h>
> > +#include <linux/btf_ids.h>
> >
> > #include <asm/page.h>
> > #include <asm/sections.h>
> > @@ -1238,3 +1240,22 @@ void __weak arch_kexec_protect_crashkres(void)
> >
> > void __weak arch_kexec_unprotect_crashkres(void)
> > {}
> > +
> > +#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
> > +BTF_SET8_START(kexec_btf_ids)
> > +BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
> > +BTF_SET8_END(kexec_btf_ids)
> > +
> > +static const struct btf_kfunc_id_set kexec_kfunc_set = {
> > + .owner = THIS_MODULE,
> > + .set = &kexec_btf_ids,
> > +};
> > +
> > +static int __init crash_kfunc_init(void)
> > +{
> > + register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &kexec_kfunc_set);
> > + return 0;
> > +}
> > +
> > +subsys_initcall(crash_kfunc_init);
> > +#endif
>
> It feels there will be a bunch of such boiler plate code
> in different .c files in many places in the kernel
> if we go with this approach.
>
> Maybe we should do one call:
> register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING
> from kernel/bpf/helper.c
> to register all tracing kfuncs ?
>
> And gate
> BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
> with #ifdef CONFIG_KEXEC_CORE.
>
> We have such a pattern in verifier.c already.
Good idea, thanks for the pointers. I'll do that in next version.
--
Artem