[RFC bpf-next 1/3] bpf: add module support to btf display helpers
From: Alan Maguire
Date: Fri Nov 13 2020 - 13:11:33 EST
bpf_snprintf_btf and bpf_seq_printf_btf use a "struct btf_ptr *"
argument that specifies type information about the type to
be displayed. Augment this information to include a module
name, allowing such display to support module types.
Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
---
include/linux/btf.h | 8 ++++++++
include/uapi/linux/bpf.h | 5 ++++-
kernel/bpf/btf.c | 18 ++++++++++++++++++
kernel/trace/bpf_trace.c | 42 ++++++++++++++++++++++++++++++++----------
tools/include/uapi/linux/bpf.h | 5 ++++-
5 files changed, 66 insertions(+), 12 deletions(-)
diff --git a/include/linux/btf.h b/include/linux/btf.h
index 2bf6418..d55ca00 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -209,6 +209,14 @@ static inline const struct btf_var_secinfo *btf_type_var_secinfo(
const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id);
const char *btf_name_by_offset(const struct btf *btf, u32 offset);
struct btf *btf_parse_vmlinux(void);
+#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+struct btf *bpf_get_btf_module(const char *name);
+#else
+static inline struct btf *bpf_get_btf_module(const char *name)
+{
+ return ERR_PTR(-ENOTSUPP);
+}
+#endif
struct btf *bpf_prog_get_target_btf(const struct bpf_prog *prog);
#else
static inline const struct btf_type *btf_type_by_id(const struct btf *btf,
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 162999b..26978be 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3636,7 +3636,8 @@ struct bpf_stack_build_id {
* the pointer data is carried out to avoid kernel crashes during
* operation. Smaller types can use string space on the stack;
* larger programs can use map data to store the string
- * representation.
+ * representation. Module-specific data structures can be
+ * displayed if the module name is supplied.
*
* The string can be subsequently shared with userspace via
* bpf_perf_event_output() or ring buffer interfaces.
@@ -5076,11 +5077,13 @@ struct bpf_sk_lookup {
* potentially to specify additional details about the BTF pointer
* (rather than its mode of display) - is included for future use.
* Display flags - BTF_F_* - are passed to bpf_snprintf_btf separately.
+ * A module name can be specified for module-specific data.
*/
struct btf_ptr {
void *ptr;
__u32 type_id;
__u32 flags; /* BTF ptr flags; unused at present. */
+ const char *module; /* optional module name. */
};
/*
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 6b2d508..3ddd1fd 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5738,6 +5738,24 @@ struct btf_module {
static LIST_HEAD(btf_modules);
static DEFINE_MUTEX(btf_module_mutex);
+struct btf *bpf_get_btf_module(const char *name)
+{
+ struct btf *btf = ERR_PTR(-ENOENT);
+ struct btf_module *btf_mod, *tmp;
+
+ mutex_lock(&btf_module_mutex);
+ list_for_each_entry_safe(btf_mod, tmp, &btf_modules, list) {
+ if (!btf_mod->btf || strcmp(name, btf_mod->btf->name) != 0)
+ continue;
+
+ refcount_inc(&btf_mod->btf->refcnt);
+ btf = btf_mod->btf;
+ break;
+ }
+ mutex_unlock(&btf_module_mutex);
+ return btf;
+}
+
static ssize_t
btf_module_read(struct file *file, struct kobject *kobj,
struct bin_attribute *bin_attr,
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index cfce60a..a4d5a26 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -73,8 +73,7 @@ static struct bpf_raw_event_map *bpf_get_raw_tracepoint_module(const char *name)
u64 bpf_get_stack(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
static int bpf_btf_printf_prepare(struct btf_ptr *ptr, u32 btf_ptr_size,
- u64 flags, const struct btf **btf,
- s32 *btf_id);
+ u64 flags, struct btf **btf, s32 *btf_id);
/**
* trace_call_bpf - invoke BPF program
@@ -784,7 +783,7 @@ struct bpf_seq_printf_buf {
BPF_CALL_4(bpf_seq_printf_btf, struct seq_file *, m, struct btf_ptr *, ptr,
u32, btf_ptr_size, u64, flags)
{
- const struct btf *btf;
+ struct btf *btf;
s32 btf_id;
int ret;
@@ -792,7 +791,11 @@ struct bpf_seq_printf_buf {
if (ret)
return ret;
- return btf_type_seq_show_flags(btf, btf_id, ptr->ptr, m, flags);
+ ret = btf_type_seq_show_flags(btf, btf_id, ptr->ptr, m, flags);
+ if (btf_ptr_size == sizeof(struct btf_ptr) && ptr->module)
+ btf_put(btf);
+
+ return ret;
}
static const struct bpf_func_proto bpf_seq_printf_btf_proto = {
@@ -1199,18 +1202,33 @@ static bool bpf_d_path_allowed(const struct bpf_prog *prog)
BTF_F_PTR_RAW | BTF_F_ZERO)
static int bpf_btf_printf_prepare(struct btf_ptr *ptr, u32 btf_ptr_size,
- u64 flags, const struct btf **btf,
+ u64 flags, struct btf **btf,
s32 *btf_id)
{
+ char modname[MODULE_NAME_LEN];
const struct btf_type *t;
+ int ret;
if (unlikely(flags & ~(BTF_F_ALL)))
return -EINVAL;
- if (btf_ptr_size != sizeof(struct btf_ptr))
+ /* For backwards compatibility, ensure that we support BPF
+ * programs compiled with older "struct btf_ptr" definitions
+ * that lacked the "module" field.
+ */
+ if (btf_ptr_size != sizeof(struct btf_ptr) &&
+ btf_ptr_size != sizeof(struct btf_ptr) - sizeof(char *))
return -EINVAL;
- *btf = bpf_get_btf_vmlinux();
+ if (btf_ptr_size == sizeof(struct btf_ptr) && ptr->module) {
+ ret = copy_from_kernel_nofault(modname, ptr->module,
+ sizeof(modname));
+ if (ret)
+ return ret;
+
+ *btf = bpf_get_btf_module(modname);
+ } else
+ *btf = bpf_get_btf_vmlinux();
if (IS_ERR_OR_NULL(*btf))
return PTR_ERR(*btf);
@@ -1231,7 +1249,7 @@ static int bpf_btf_printf_prepare(struct btf_ptr *ptr, u32 btf_ptr_size,
BPF_CALL_5(bpf_snprintf_btf, char *, str, u32, str_size, struct btf_ptr *, ptr,
u32, btf_ptr_size, u64, flags)
{
- const struct btf *btf;
+ struct btf *btf;
s32 btf_id;
int ret;
@@ -1239,8 +1257,12 @@ static int bpf_btf_printf_prepare(struct btf_ptr *ptr, u32 btf_ptr_size,
if (ret)
return ret;
- return btf_type_snprintf_show(btf, btf_id, ptr->ptr, str, str_size,
- flags);
+ ret = btf_type_snprintf_show(btf, btf_id, ptr->ptr, str, str_size,
+ flags);
+ if (btf_ptr_size == sizeof(struct btf_ptr) && ptr->module)
+ btf_put(btf);
+
+ return ret;
}
const struct bpf_func_proto bpf_snprintf_btf_proto = {
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 162999b..26978be 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3636,7 +3636,8 @@ struct bpf_stack_build_id {
* the pointer data is carried out to avoid kernel crashes during
* operation. Smaller types can use string space on the stack;
* larger programs can use map data to store the string
- * representation.
+ * representation. Module-specific data structures can be
+ * displayed if the module name is supplied.
*
* The string can be subsequently shared with userspace via
* bpf_perf_event_output() or ring buffer interfaces.
@@ -5076,11 +5077,13 @@ struct bpf_sk_lookup {
* potentially to specify additional details about the BTF pointer
* (rather than its mode of display) - is included for future use.
* Display flags - BTF_F_* - are passed to bpf_snprintf_btf separately.
+ * A module name can be specified for module-specific data.
*/
struct btf_ptr {
void *ptr;
__u32 type_id;
__u32 flags; /* BTF ptr flags; unused at present. */
+ const char *module; /* optional module name. */
};
/*
--
1.8.3.1