From 792001f4f7aa036b1f1c1ed7bce44bb49126208a Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Fri, 18 Dec 2020 15:56:12 -0800 Subject: libbpf: Add user-space variants of BPF_CORE_READ() family of macros Add BPF_CORE_READ_USER(), BPF_CORE_READ_USER_STR() and their _INTO() variations to allow reading CO-RE-relocatable kernel data structures from the user-space. One of such cases is reading input arguments of syscalls, while reaping the benefits of CO-RE relocations w.r.t. handling 32/64 bit conversions and handling missing/new fields in UAPI data structs. Suggested-by: Gilad Reti Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20201218235614.2284956-2-andrii@kernel.org Signed-off-by: Alexei Starovoitov --- tools/lib/bpf/bpf_core_read.h | 98 ++++++++++++++++++++++++++----------------- 1 file changed, 59 insertions(+), 39 deletions(-) (limited to 'tools/lib/bpf') diff --git a/tools/lib/bpf/bpf_core_read.h b/tools/lib/bpf/bpf_core_read.h index bbcefb3ff5a5..db0c735ceb53 100644 --- a/tools/lib/bpf/bpf_core_read.h +++ b/tools/lib/bpf/bpf_core_read.h @@ -195,17 +195,20 @@ enum bpf_enum_value_kind { * (local) BTF, used to record relocation. */ #define bpf_core_read(dst, sz, src) \ - bpf_probe_read_kernel(dst, sz, \ - (const void *)__builtin_preserve_access_index(src)) + bpf_probe_read_kernel(dst, sz, (const void *)__builtin_preserve_access_index(src)) +#define bpf_core_read_user(dst, sz, src) \ + bpf_probe_read_user(dst, sz, (const void *)__builtin_preserve_access_index(src)) /* * bpf_core_read_str() is a thin wrapper around bpf_probe_read_str() * additionally emitting BPF CO-RE field relocation for specified source * argument. */ #define bpf_core_read_str(dst, sz, src) \ - bpf_probe_read_kernel_str(dst, sz, \ - (const void *)__builtin_preserve_access_index(src)) + bpf_probe_read_kernel_str(dst, sz, (const void *)__builtin_preserve_access_index(src)) + +#define bpf_core_read_user_str(dst, sz, src) \ + bpf_probe_read_user_str(dst, sz, (const void *)__builtin_preserve_access_index(src)) #define ___concat(a, b) a ## b #define ___apply(fn, n) ___concat(fn, n) @@ -264,30 +267,29 @@ enum bpf_enum_value_kind { read_fn((void *)(dst), sizeof(*(dst)), &((src_type)(src))->accessor) /* "recursively" read a sequence of inner pointers using local __t var */ -#define ___rd_first(src, a) ___read(bpf_core_read, &__t, ___type(src), src, a); -#define ___rd_last(...) \ - ___read(bpf_core_read, &__t, \ - ___type(___nolast(__VA_ARGS__)), __t, ___last(__VA_ARGS__)); -#define ___rd_p1(...) const void *__t; ___rd_first(__VA_ARGS__) -#define ___rd_p2(...) ___rd_p1(___nolast(__VA_ARGS__)) ___rd_last(__VA_ARGS__) -#define ___rd_p3(...) ___rd_p2(___nolast(__VA_ARGS__)) ___rd_last(__VA_ARGS__) -#define ___rd_p4(...) ___rd_p3(___nolast(__VA_ARGS__)) ___rd_last(__VA_ARGS__) -#define ___rd_p5(...) ___rd_p4(___nolast(__VA_ARGS__)) ___rd_last(__VA_ARGS__) -#define ___rd_p6(...) ___rd_p5(___nolast(__VA_ARGS__)) ___rd_last(__VA_ARGS__) -#define ___rd_p7(...) ___rd_p6(___nolast(__VA_ARGS__)) ___rd_last(__VA_ARGS__) -#define ___rd_p8(...) ___rd_p7(___nolast(__VA_ARGS__)) ___rd_last(__VA_ARGS__) -#define ___rd_p9(...) ___rd_p8(___nolast(__VA_ARGS__)) ___rd_last(__VA_ARGS__) -#define ___read_ptrs(src, ...) \ - ___apply(___rd_p, ___narg(__VA_ARGS__))(src, __VA_ARGS__) - -#define ___core_read0(fn, dst, src, a) \ +#define ___rd_first(fn, src, a) ___read(fn, &__t, ___type(src), src, a); +#define ___rd_last(fn, ...) \ + ___read(fn, &__t, ___type(___nolast(__VA_ARGS__)), __t, ___last(__VA_ARGS__)); +#define ___rd_p1(fn, ...) const void *__t; ___rd_first(fn, __VA_ARGS__) +#define ___rd_p2(fn, ...) ___rd_p1(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__) +#define ___rd_p3(fn, ...) ___rd_p2(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__) +#define ___rd_p4(fn, ...) ___rd_p3(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__) +#define ___rd_p5(fn, ...) ___rd_p4(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__) +#define ___rd_p6(fn, ...) ___rd_p5(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__) +#define ___rd_p7(fn, ...) ___rd_p6(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__) +#define ___rd_p8(fn, ...) ___rd_p7(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__) +#define ___rd_p9(fn, ...) ___rd_p8(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__) +#define ___read_ptrs(fn, src, ...) \ + ___apply(___rd_p, ___narg(__VA_ARGS__))(fn, src, __VA_ARGS__) + +#define ___core_read0(fn, fn_ptr, dst, src, a) \ ___read(fn, dst, ___type(src), src, a); -#define ___core_readN(fn, dst, src, ...) \ - ___read_ptrs(src, ___nolast(__VA_ARGS__)) \ +#define ___core_readN(fn, fn_ptr, dst, src, ...) \ + ___read_ptrs(fn_ptr, src, ___nolast(__VA_ARGS__)) \ ___read(fn, dst, ___type(src, ___nolast(__VA_ARGS__)), __t, \ ___last(__VA_ARGS__)); -#define ___core_read(fn, dst, src, a, ...) \ - ___apply(___core_read, ___empty(__VA_ARGS__))(fn, dst, \ +#define ___core_read(fn, fn_ptr, dst, src, a, ...) \ + ___apply(___core_read, ___empty(__VA_ARGS__))(fn, fn_ptr, dst, \ src, a, ##__VA_ARGS__) /* @@ -295,20 +297,32 @@ enum bpf_enum_value_kind { * BPF_CORE_READ(), in which final field is read into user-provided storage. * See BPF_CORE_READ() below for more details on general usage. */ -#define BPF_CORE_READ_INTO(dst, src, a, ...) \ - ({ \ - ___core_read(bpf_core_read, dst, (src), a, ##__VA_ARGS__) \ - }) +#define BPF_CORE_READ_INTO(dst, src, a, ...) ({ \ + ___core_read(bpf_core_read, bpf_core_read, \ + dst, (src), a, ##__VA_ARGS__) \ +}) + +/* Variant of BPF_CORE_READ_INTO() for reading from user-space memory */ +#define BPF_CORE_READ_USER_INTO(dst, src, a, ...) ({ \ + ___core_read(bpf_core_read_user, bpf_core_read_user, \ + dst, (src), a, ##__VA_ARGS__) \ +}) /* * BPF_CORE_READ_STR_INTO() does same "pointer chasing" as * BPF_CORE_READ() for intermediate pointers, but then executes (and returns * corresponding error code) bpf_core_read_str() for final string read. */ -#define BPF_CORE_READ_STR_INTO(dst, src, a, ...) \ - ({ \ - ___core_read(bpf_core_read_str, dst, (src), a, ##__VA_ARGS__)\ - }) +#define BPF_CORE_READ_STR_INTO(dst, src, a, ...) ({ \ + ___core_read(bpf_core_read_str, bpf_core_read, \ + dst, (src), a, ##__VA_ARGS__) \ +}) + +/* Variant of BPF_CORE_READ_STR_INTO() for reading from user-space memory */ +#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__) \ +}) /* * BPF_CORE_READ() is used to simplify BPF CO-RE relocatable read, especially @@ -334,12 +348,18 @@ enum bpf_enum_value_kind { * N.B. Only up to 9 "field accessors" are supported, which should be more * than enough for any practical purpose. */ -#define BPF_CORE_READ(src, a, ...) \ - ({ \ - ___type((src), a, ##__VA_ARGS__) __r; \ - BPF_CORE_READ_INTO(&__r, (src), a, ##__VA_ARGS__); \ - __r; \ - }) +#define BPF_CORE_READ(src, a, ...) ({ \ + ___type((src), a, ##__VA_ARGS__) __r; \ + BPF_CORE_READ_INTO(&__r, (src), a, ##__VA_ARGS__); \ + __r; \ +}) + +/* Variant of BPF_CORE_READ() for reading from user-space memory */ +#define BPF_CORE_READ_USER(src, a, ...) ({ \ + ___type((src), a, ##__VA_ARGS__) __r; \ + BPF_CORE_READ_USER_INTO(&__r, (src), a, ##__VA_ARGS__); \ + __r; \ +}) #endif -- cgit v1.2.3