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Wang Nan 098d2164e3 bpf: Use correct #ifdef controller for trace_call_bpf() 
Commit e1abf2cc8d ("bpf: Fix the build on
BPF_SYSCALL=y && !CONFIG_TRACING kernels, make it more configurable")
updated the building condition of bpf_trace.o from CONFIG_BPF_SYSCALL
to CONFIG_BPF_EVENTS, but the corresponding #ifdef controller in
trace_events.h for trace_call_bpf() was not changed. Which, in theory,
is incorrect.

With current Kconfigs, we can create a .config with CONFIG_BPF_SYSCALL=y
and CONFIG_BPF_EVENTS=n by unselecting CONFIG_KPROBE_EVENT and
selecting CONFIG_BPF_SYSCALL. With these options, trace_call_bpf() will
be defined as an extern function, but if anyone calls it a symbol missing
error will be triggered since bpf_trace.o was not built.

This patch changes the #ifdef controller for trace_call_bpf() from
CONFIG_BPF_SYSCALL to CONFIG_BPF_EVENTS. I'll show its correctness:

Before this patch:

   BPF_SYSCALL   BPF_EVENTS   trace_call_bpf   bpf_trace.o
   y             y           normal           compiled
   n             n           inline           not compiled
   y             n           normal           not compiled (incorrect)
   n             y          impossible (BPF_EVENTS depends on BPF_SYSCALL)

After this patch:

   BPF_SYSCALL   BPF_EVENTS   trace_call_bpf   bpf_trace.o
   y             y           normal           compiled
   n             n           inline           not compiled
   y             n           inline           not compiled (fixed)
   n             y          impossible (BPF_EVENTS depends on BPF_SYSCALL)

So this patch doesn't break anything. QED.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kaixu Xia <xiakaixu@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1435716878-189507-2-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
 		2015-08-06 15:27:37 -03:00
..
acpi Additional ACPICA material for v4.2-rc1 2015-07-02 17:11:28 -07:00
asm-generic mm: clean up per architecture MM hook header files 2015-07-17 16:39:53 -07:00
clocksource
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crypto crypto: rng - Do not free default RNG when it becomes unused 2015-06-22 15:49:18 +08:00
drm drm: use kvfree() in drm_free_large() 2015-06-30 19:44:59 -07:00
dt-bindings The changes to the common clock framework for 4.2 are dominated by new 2015-07-01 19:22:00 -07:00
keys
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kvm
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linux bpf: Use correct #ifdef controller for trace_call_bpf() 2015-08-06 15:27:37 -03:00
math-emu
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media Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/cooloney/linux-leds 2015-07-01 19:09:11 -07:00
memory
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misc
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net Some fixes for the current cycle: 2015-07-21 00:17:53 -07:00
pcmcia
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ras tracing: add trace event for memory-failure 2015-06-24 17:49:43 -07:00
rdma IB: Add rdma_cap_ib_switch helper and use where appropriate 2015-07-14 13:20:08 -04:00
rxrpc
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scsi IB/srp: Avoid using uninitialized variable 2015-07-14 13:20:09 -04:00
soc Merge branch 'for-linus' of git://ftp.arm.linux.org.uk/~rmk/linux-arm 2015-06-26 12:20:00 -07:00
sound ASoC: Further updates for v4.2 2015-06-22 11:32:41 +02:00
target Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending 2015-07-04 14:13:43 -07:00
trace Merge branch 'for-linus-4.2' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs 2015-06-30 20:07:45 -07:00
uapi perf: Add cycles to branch_info 2015-08-04 10:16:57 +02:00
video Merge branch 'drm-next' of git://people.freedesktop.org/~airlied/linux 2015-06-26 13:18:51 -07:00
xen
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Kbuild
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