bpf: Fix BPF_JIT kconfig symbol dependency

Randy reported a randconfig build error recently on i386:

  ld: arch/x86/net/bpf_jit_comp32.o: in function `do_jit':
  bpf_jit_comp32.c:(.text+0x28c9): undefined reference to `__bpf_call_base'
  ld: arch/x86/net/bpf_jit_comp32.o: in function `bpf_int_jit_compile':
  bpf_jit_comp32.c:(.text+0x3694): undefined reference to `bpf_jit_blind_constants'
  ld: bpf_jit_comp32.c:(.text+0x3719): undefined reference to `bpf_jit_binary_free'
  ld: bpf_jit_comp32.c:(.text+0x3745): undefined reference to `bpf_jit_binary_alloc'
  ld: bpf_jit_comp32.c:(.text+0x37d3): undefined reference to `bpf_jit_prog_release_other'
  [...]

The cause was that b24abcff918a ("bpf, kconfig: Add consolidated menu entry for
bpf with core options") moved BPF_JIT from net/Kconfig into kernel/bpf/Kconfig
and previously BPF_JIT was guarded by a 'if NET'. However, there is no actual
dependency on NET, it's just that menuconfig NET selects BPF. And the latter in
turn causes kernel/bpf/core.o to be built which contains above symbols. Randy's
randconfig didn't have NET set, and BPF wasn't either, but BPF_JIT otoh was.
Detangle this by making BPF_JIT depend on BPF instead. arm64 was the only arch
that pulled in its JIT in net/ via obj-$(CONFIG_NET), all others unconditionally
pull this dir in via obj-y. Do the same since CONFIG_NET guard there is really
useless as we compiled the JIT via obj-$(CONFIG_BPF_JIT) += bpf_jit_comp.o anyway.

Fixes: b24abcff918a ("bpf, kconfig: Add consolidated menu entry for bpf with core options")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>

diff --git a/arch/arm64/Kbuild b/arch/arm64/Kbuild
index d646582..7b393cf 100644 (file)
--- a/arch/arm64/Kbuild
+++ b/arch/arm64/Kbuild
@@ -1,6 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0-only
-obj-y                  += kernel/ mm/
-obj-$(CONFIG_NET)      += net/
+obj-y                  += kernel/ mm/ net/
 obj-$(CONFIG_KVM)      += kvm/
 obj-$(CONFIG_XEN)      += xen/
 obj-$(CONFIG_CRYPTO)   += crypto/

diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig
index 26b591e..bd04f4a 100644 (file)
--- a/kernel/bpf/Kconfig
+++ b/kernel/bpf/Kconfig
@@ -37,6 +37,7 @@ config BPF_SYSCALL
 
 config BPF_JIT
        bool "Enable BPF Just In Time compiler"
+       depends on BPF
        depends on HAVE_CBPF_JIT || HAVE_EBPF_JIT
        depends on MODULES
        help