LLVM generates bpf_addr_space_cast instruction while translating pointers between native (zero) address space and __attribute__((address_space(N))). The addr_space=1 is reserved as bpf_arena address space. rY = addr_space_cast(rX, 0, 1) is processed by the verifier and converted to normal 32-bit move: wX = wY rY = addr_space_cast(rX, 1, 0) has to be converted by JIT: aux_reg = upper_32_bits of arena->user_vm_start aux_reg <<= 32 wX = wY // clear upper 32 bits of dst register if (wX) // if not zero add upper bits of user_vm_start wX |= aux_reg JIT can do it more efficiently: mov dst_reg32, src_reg32 // 32-bit move shl dst_reg, 32 or dst_reg, user_vm_start rol dst_reg, 32 xor r11, r11 test dst_reg32, dst_reg32 // check if lower 32-bit are zero cmove r11, dst_reg // if so, set dst_reg to zero // Intel swapped src/dst register encoding in CMOVcc Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/bpf/20240308010812.89848-5-alexei.starovoitov@gmail.com
Add support for [LDX | STX | ST], PROBE_MEM32, [B | H | W | DW] instructions. They are similar to PROBE_MEM instructions with the following differences: - PROBE_MEM has to check that the address is in the kernel range with src_reg + insn->off >= TASK_SIZE_MAX + PAGE_SIZE check - PROBE_MEM doesn't support store - PROBE_MEM32 relies on the verifier to clear upper 32-bit in the register - PROBE_MEM32 adds 64-bit kern_vm_start address (which is stored in %r12 in the prologue) Due to bpf_arena constructions such %r12 + %reg + off16 access is guaranteed to be within arena virtual range, so no address check at run-time. - PROBE_MEM32 allows STX and ST. If they fault the store is a nop. When LDX faults the destination register is zeroed. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/bpf/20240308010812.89848-4-alexei.starovoitov@gmail.com
Currently tracing is supposed not to allow for bpf_spin_{lock,unlock}()
helper calls. This is to prevent deadlock for the following cases:
- there is a prog (prog-A) calling bpf_spin_{lock,unlock}().
- there is a tracing program (prog-B), e.g., fentry, attached
to bpf_spin_lock() and/or bpf_spin_unlock().
- prog-B calls bpf_spin_{lock,unlock}().
For such a case, when prog-A calls bpf_spin_{lock,unlock}(),
a deadlock will happen.
The related source codes are below in kernel/bpf/helpers.c:
notrace BPF_CALL_1(bpf_spin_lock, struct bpf_spin_lock *, lock)
notrace BPF_CALL_1(bpf_spin_unlock, struct bpf_spin_lock *, lock)
notrace is supposed to prevent fentry prog from attaching to
bpf_spin_{lock,unlock}().
But actually this is not the case and fentry prog can successfully
attached to bpf_spin_lock(). Siddharth Chintamaneni reported
the issue in [1]. The following is the macro definition for
above BPF_CALL_1:
#define BPF_CALL_x(x, name, ...) \
static __always_inline \
u64 ____##name(__BPF_MAP(x, __BPF_DECL_ARGS, __BPF_V, __VA_ARGS__)); \
typedef u64 (*btf_##name)(__BPF_MAP(x, __BPF_DECL_ARGS, __BPF_V, __VA_ARGS__)); \
u64 name(__BPF_REG(x, __BPF_DECL_REGS, __BPF_N, __VA_ARGS__)); \
u64 name(__BPF_REG(x, __BPF_DECL_REGS, __BPF_N, __VA_ARGS__)) \
{ \
return ((btf_##name)____##name)(__BPF_MAP(x,__BPF_CAST,__BPF_N,__VA_ARGS__));\
} \
static __always_inline \
u64 ____##name(__BPF_MAP(x, __BPF_DECL_ARGS, __BPF_V, __VA_ARGS__))
#define BPF_CALL_1(name, ...) BPF_CALL_x(1, name, __VA_ARGS__)
The notrace attribute is actually applied to the static always_inline function
____bpf_spin_{lock,unlock}(). The actual callback function
bpf_spin_{lock,unlock}() is not marked with notrace, hence
allowing fentry prog to attach to two helpers, and this
may cause the above mentioned deadlock. Siddharth Chintamaneni
actually has a reproducer in [2].
To fix the issue, a new macro NOTRACE_BPF_CALL_1 is introduced which
will add notrace attribute to the original function instead of
the hidden always_inline function and this fixed the problem.
[1] https://lore.kernel.org/bpf/CAE5sdEigPnoGrzN8WU7Tx-h-iFuMZgW06qp0KHWtpvoXxf1OAQ@mail.gmail.com/
[2] https://lore.kernel.org/bpf/CAE5sdEg6yUc_Jz50AnUXEEUh6O73yQ1Z6NV2srJnef0ZrQkZew@mail.gmail.com/
Fixes: d83525ca62cf ("bpf: introduce bpf_spin_lock")
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20240207070102.335167-1-yonghong.song@linux.dev
Remove remaining direct queries to perfmon_capable() and bpf_capable() in BPF verifier logic and instead use BPF token (if available) to make decisions about privileges. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20240124022127.2379740-9-andrii@kernel.org
The motivation of inlining bpf_kptr_xchg() comes from the performance profiling of bpf memory allocator benchmark. The benchmark uses bpf_kptr_xchg() to stash the allocated objects and to pop the stashed objects for free. After inling bpf_kptr_xchg(), the performance for object free on 8-CPUs VM increases about 2%~10%. The inline also has downside: both the kasan and kcsan checks on the pointer will be unavailable. bpf_kptr_xchg() can be inlined by converting the calling of bpf_kptr_xchg() into an atomic_xchg() instruction. But the conversion depends on two conditions: 1) JIT backend supports atomic_xchg() on pointer-sized word 2) For the specific arch, the implementation of xchg is the same as atomic_xchg() on pointer-sized words. It seems most 64-bit JIT backends satisfies these two conditions. But as a precaution, defining a weak function bpf_jit_supports_ptr_xchg() to state whether such conversion is safe and only supporting inline for 64-bit host. For x86-64, it supports BPF_XCHG atomic operation and both xchg() and atomic_xchg() use arch_xchg() to implement the exchange, so enabling the inline of bpf_kptr_xchg() on x86-64 first. Reviewed-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Hou Tao <houtao1@huawei.com> Link: https://lore.kernel.org/r/20240105104819.3916743-2-houtao@huaweicloud.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This patch includes the following revert (one conflicting BPF FS patch and three token patch sets, represented by merge commits): - revert 0f5d5454c723 "Merge branch 'bpf-fs-mount-options-parsing-follow-ups'"; - revert 750e785796bb "bpf: Support uid and gid when mounting bpffs"; - revert 733763285acf "Merge branch 'bpf-token-support-in-libbpf-s-bpf-object'"; - revert c35919dcce28 "Merge branch 'bpf-token-and-bpf-fs-based-delegation'". Link: https://lore.kernel.org/bpf/CAHk-=wg7JuFYwGy=GOMbRCtOL+jwSQsdUaBsRWkDVYbxipbM5A@mail.gmail.com Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Currently, bpf_prog_pack_free only can only free pointer to struct bpf_binary_header, which is not flexible. Add a size argument to bpf_prog_pack_free so that it can handle any pointer. Signed-off-by: Song Liu <song@kernel.org> Acked-by: Ilya Leoshkevich <iii@linux.ibm.com> Tested-by: Ilya Leoshkevich <iii@linux.ibm.com> # on s390x Reviewed-by: Björn Töpel <bjorn@rivosinc.com> Acked-by: Jiri Olsa <jolsa@kernel.org> Link: https://lore.kernel.org/r/20231206224054.492250-2-song@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Remove remaining direct queries to perfmon_capable() and bpf_capable() in BPF verifier logic and instead use BPF token (if available) to make decisions about privileges. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20231130185229.2688956-9-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Daniel Borkmann says:
====================
pull-request: bpf-next 2023-10-16
We've added 90 non-merge commits during the last 25 day(s) which contain
a total of 120 files changed, 3519 insertions(+), 895 deletions(-).
The main changes are:
1) Add missed stats for kprobes to retrieve the number of missed kprobe
executions and subsequent executions of BPF programs, from Jiri Olsa.
2) Add cgroup BPF sockaddr hooks for unix sockets. The use case is
for systemd to reimplement the LogNamespace feature which allows
running multiple instances of systemd-journald to process the logs
of different services, from Daan De Meyer.
3) Implement BPF CPUv4 support for s390x BPF JIT, from Ilya Leoshkevich.
4) Improve BPF verifier log output for scalar registers to better
disambiguate their internal state wrt defaults vs min/max values
matching, from Andrii Nakryiko.
5) Extend the BPF fib lookup helpers for IPv4/IPv6 to support retrieving
the source IP address with a new BPF_FIB_LOOKUP_SRC flag,
from Martynas Pumputis.
6) Add support for open-coded task_vma iterator to help with symbolization
for BPF-collected user stacks, from Dave Marchevsky.
7) Add libbpf getters for accessing individual BPF ring buffers which
is useful for polling them individually, for example, from Martin Kelly.
8) Extend AF_XDP selftests to validate the SHARED_UMEM feature,
from Tushar Vyavahare.
9) Improve BPF selftests cross-building support for riscv arch,
from Björn Töpel.
10) Add the ability to pin a BPF timer to the same calling CPU,
from David Vernet.
11) Fix libbpf's bpf_tracing.h macros for riscv to use the generic
implementation of PT_REGS_SYSCALL_REGS() to access syscall arguments,
from Alexandre Ghiti.
12) Extend libbpf to support symbol versioning for uprobes, from Hengqi Chen.
13) Fix bpftool's skeleton code generation to guarantee that ELF data
is 8 byte aligned, from Ian Rogers.
14) Inherit system-wide cpu_mitigations_off() setting for Spectre v1/v4
security mitigations in BPF verifier, from Yafang Shao.
15) Annotate struct bpf_stack_map with __counted_by attribute to prepare
BPF side for upcoming __counted_by compiler support, from Kees Cook.
* tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (90 commits)
bpf: Ensure proper register state printing for cond jumps
bpf: Disambiguate SCALAR register state output in verifier logs
selftests/bpf: Make align selftests more robust
selftests/bpf: Improve missed_kprobe_recursion test robustness
selftests/bpf: Improve percpu_alloc test robustness
selftests/bpf: Add tests for open-coded task_vma iter
bpf: Introduce task_vma open-coded iterator kfuncs
selftests/bpf: Rename bpf_iter_task_vma.c to bpf_iter_task_vmas.c
bpf: Don't explicitly emit BTF for struct btf_iter_num
bpf: Change syscall_nr type to int in struct syscall_tp_t
net/bpf: Avoid unused "sin_addr_len" warning when CONFIG_CGROUP_BPF is not set
bpf: Avoid unnecessary audit log for CPU security mitigations
selftests/bpf: Add tests for cgroup unix socket address hooks
selftests/bpf: Make sure mount directory exists
documentation/bpf: Document cgroup unix socket address hooks
bpftool: Add support for cgroup unix socket address hooks
libbpf: Add support for cgroup unix socket address hooks
bpf: Implement cgroup sockaddr hooks for unix sockets
bpf: Add bpf_sock_addr_set_sun_path() to allow writing unix sockaddr from bpf
bpf: Propagate modified uaddrlen from cgroup sockaddr programs
...
====================
Link: https://lore.kernel.org/r/20231016204803.30153-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
As prep for adding unix socket support to the cgroup sockaddr hooks, let's propagate the sockaddr length back to the caller after running a bpf cgroup sockaddr hook program. While not important for AF_INET or AF_INET6, the sockaddr length is important when working with AF_UNIX sockaddrs as the size of the sockaddr cannot be determined just from the address family or the sockaddr's contents. __cgroup_bpf_run_filter_sock_addr() is modified to take the uaddrlen as an input/output argument. After running the program, the modified sockaddr length is stored in the uaddrlen pointer. Signed-off-by: Daan De Meyer <daan.j.demeyer@gmail.com> Link: https://lore.kernel.org/r/20231011185113.140426-3-daan.j.demeyer@gmail.com Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>