ef7fe1b5c4
[ Upstream commit bdeeed3498c7871c17465bb4f11d1bc67f9098af ]
It seems like __builtin_offset() doesn't preserve CO-RE field
relocations properly. So if offsetof() macro is defined through
__builtin_offset(), CO-RE-enabled BPF code using container_of() will be
subtly and silently broken.
To avoid this problem, redefine offsetof() and container_of() in the
form that works with CO-RE relocations more reliably.
Fixes: 5fbc220862 ("tools/libpf: Add offsetof/container_of macro in bpf_helpers.h")
Reported-by: Lennart Poettering <lennart@poettering.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20230509065502.2306180-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
137 lines
4.0 KiB
C
137 lines
4.0 KiB
C
/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
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#ifndef __BPF_HELPERS__
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#define __BPF_HELPERS__
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/*
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* Note that bpf programs need to include either
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* vmlinux.h (auto-generated from BTF) or linux/types.h
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* in advance since bpf_helper_defs.h uses such types
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* as __u64.
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*/
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#include "bpf_helper_defs.h"
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#define __uint(name, val) int (*name)[val]
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#define __type(name, val) typeof(val) *name
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#define __array(name, val) typeof(val) *name[]
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/* Helper macro to print out debug messages */
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#define bpf_printk(fmt, ...) \
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({ \
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char ____fmt[] = fmt; \
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bpf_trace_printk(____fmt, sizeof(____fmt), \
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##__VA_ARGS__); \
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})
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/*
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* Helper macro to place programs, maps, license in
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* different sections in elf_bpf file. Section names
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* are interpreted by elf_bpf loader
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*/
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#define SEC(NAME) __attribute__((section(NAME), used))
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#ifndef __always_inline
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#define __always_inline __attribute__((always_inline))
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#endif
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#ifndef __noinline
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#define __noinline __attribute__((noinline))
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#endif
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#ifndef __weak
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#define __weak __attribute__((weak))
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#endif
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/*
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* Helper macro to manipulate data structures
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*/
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/* offsetof() definition that uses __builtin_offset() might not preserve field
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* offset CO-RE relocation properly, so force-redefine offsetof() using
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* old-school approach which works with CO-RE correctly
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*/
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#undef offsetof
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#define offsetof(type, member) ((unsigned long)&((type *)0)->member)
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/* redefined container_of() to ensure we use the above offsetof() macro */
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#undef container_of
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#define container_of(ptr, type, member) \
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({ \
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void *__mptr = (void *)(ptr); \
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((type *)(__mptr - offsetof(type, member))); \
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})
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/*
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* Helper macro to throw a compilation error if __bpf_unreachable() gets
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* built into the resulting code. This works given BPF back end does not
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* implement __builtin_trap(). This is useful to assert that certain paths
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* of the program code are never used and hence eliminated by the compiler.
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*
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* For example, consider a switch statement that covers known cases used by
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* the program. __bpf_unreachable() can then reside in the default case. If
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* the program gets extended such that a case is not covered in the switch
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* statement, then it will throw a build error due to the default case not
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* being compiled out.
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*/
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#ifndef __bpf_unreachable
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# define __bpf_unreachable() __builtin_trap()
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#endif
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/*
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* Helper function to perform a tail call with a constant/immediate map slot.
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*/
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#if __clang_major__ >= 8 && defined(__bpf__)
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static __always_inline void
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bpf_tail_call_static(void *ctx, const void *map, const __u32 slot)
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{
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if (!__builtin_constant_p(slot))
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__bpf_unreachable();
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/*
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* Provide a hard guarantee that LLVM won't optimize setting r2 (map
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* pointer) and r3 (constant map index) from _different paths_ ending
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* up at the _same_ call insn as otherwise we won't be able to use the
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* jmpq/nopl retpoline-free patching by the x86-64 JIT in the kernel
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* given they mismatch. See also d2e4c1e6c294 ("bpf: Constant map key
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* tracking for prog array pokes") for details on verifier tracking.
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*
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* Note on clobber list: we need to stay in-line with BPF calling
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* convention, so even if we don't end up using r0, r4, r5, we need
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* to mark them as clobber so that LLVM doesn't end up using them
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* before / after the call.
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*/
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asm volatile("r1 = %[ctx]\n\t"
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"r2 = %[map]\n\t"
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"r3 = %[slot]\n\t"
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"call 12"
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:: [ctx]"r"(ctx), [map]"r"(map), [slot]"i"(slot)
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: "r0", "r1", "r2", "r3", "r4", "r5");
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}
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#endif
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/*
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* Helper structure used by eBPF C program
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* to describe BPF map attributes to libbpf loader
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*/
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struct bpf_map_def {
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unsigned int type;
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unsigned int key_size;
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unsigned int value_size;
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unsigned int max_entries;
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unsigned int map_flags;
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};
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enum libbpf_pin_type {
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LIBBPF_PIN_NONE,
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/* PIN_BY_NAME: pin maps by name (in /sys/fs/bpf by default) */
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LIBBPF_PIN_BY_NAME,
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};
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enum libbpf_tristate {
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TRI_NO = 0,
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TRI_YES = 1,
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TRI_MODULE = 2,
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};
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#define __kconfig __attribute__((section(".kconfig")))
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#define __ksym __attribute__((section(".ksyms")))
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#endif
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