#define bpf_core_read(dst, sz, src) \
bpf_probe_read_kernel(dst, sz, (const void *)__builtin_preserve_access_index(src))
+/* NOTE: see comments for BPF_CORE_READ_USER() about the proper types use. */
#define bpf_core_read_user(dst, sz, src) \
bpf_probe_read_user(dst, sz, (const void *)__builtin_preserve_access_index(src))
/*
#define bpf_core_read_str(dst, sz, src) \
bpf_probe_read_kernel_str(dst, sz, (const void *)__builtin_preserve_access_index(src))
+/* NOTE: see comments for BPF_CORE_READ_USER() about the proper types use. */
#define bpf_core_read_user_str(dst, sz, src) \
bpf_probe_read_user_str(dst, sz, (const void *)__builtin_preserve_access_index(src))
dst, (src), a, ##__VA_ARGS__) \
})
-/* Variant of BPF_CORE_READ_INTO() for reading from user-space memory */
+/*
+ * Variant of BPF_CORE_READ_INTO() for reading from user-space memory.
+ *
+ * NOTE: see comments for BPF_CORE_READ_USER() about the proper types use.
+ */
#define BPF_CORE_READ_USER_INTO(dst, src, a, ...) ({ \
___core_read(bpf_core_read_user, bpf_core_read_user, \
dst, (src), a, ##__VA_ARGS__) \
dst, (src), a, ##__VA_ARGS__) \
})
-/* Non-CO-RE variant of BPF_CORE_READ_USER_INTO() */
+/* Non-CO-RE variant of BPF_CORE_READ_USER_INTO().
+ *
+ * As no CO-RE relocations are emitted, source types can be arbitrary and are
+ * not restricted to kernel types only.
+ */
#define BPF_PROBE_READ_USER_INTO(dst, src, a, ...) ({ \
___core_read(bpf_probe_read_user, bpf_probe_read_user, \
dst, (src), a, ##__VA_ARGS__) \
dst, (src), a, ##__VA_ARGS__) \
})
-/* Variant of BPF_CORE_READ_STR_INTO() for reading from user-space memory */
+/*
+ * Variant of BPF_CORE_READ_STR_INTO() for reading from user-space memory.
+ *
+ * NOTE: see comments for BPF_CORE_READ_USER() about the proper types use.
+ */
#define BPF_CORE_READ_USER_STR_INTO(dst, src, a, ...) ({ \
___core_read(bpf_core_read_user_str, bpf_core_read_user, \
dst, (src), a, ##__VA_ARGS__) \
dst, (src), a, ##__VA_ARGS__) \
})
-/* Non-CO-RE variant of BPF_CORE_READ_USER_STR_INTO() */
+/*
+ * Non-CO-RE variant of BPF_CORE_READ_USER_STR_INTO().
+ *
+ * As no CO-RE relocations are emitted, source types can be arbitrary and are
+ * not restricted to kernel types only.
+ */
#define BPF_PROBE_READ_USER_STR_INTO(dst, src, a, ...) ({ \
___core_read(bpf_probe_read_user_str, bpf_probe_read_user, \
dst, (src), a, ##__VA_ARGS__) \
__r; \
})
-/* Variant of BPF_CORE_READ() for reading from user-space memory */
+/*
+ * Variant of BPF_CORE_READ() for reading from user-space memory.
+ *
+ * NOTE: all the source types involved are still *kernel types* and need to
+ * exist in kernel (or kernel module) BTF, otherwise CO-RE relocation will
+ * fail. Custom user types are not relocatable with CO-RE.
+ * The typical situation in which BPF_CORE_READ_USER() might be used is to
+ * read kernel UAPI types from the user-space memory passed in as a syscall
+ * input argument.
+ */
#define BPF_CORE_READ_USER(src, a, ...) ({ \
___type((src), a, ##__VA_ARGS__) __r; \
BPF_CORE_READ_USER_INTO(&__r, (src), a, ##__VA_ARGS__); \
__r; \
})
-/* Non-CO-RE variant of BPF_CORE_READ_USER() */
+/*
+ * Non-CO-RE variant of BPF_CORE_READ_USER().
+ *
+ * As no CO-RE relocations are emitted, source types can be arbitrary and are
+ * not restricted to kernel types only.
+ */
#define BPF_PROBE_READ_USER(src, a, ...) ({ \
___type((src), a, ##__VA_ARGS__) __r; \
BPF_PROBE_READ_USER_INTO(&__r, (src), a, ##__VA_ARGS__); \