[PATCH net-next] bpf: bpf_stackmap_copy depends on CONFIG_PERF_EVENTS

[PATCH net-next] bpf: bpf_stackmap_copy depends on CONFIG_PERF_EVENTS

[Alexei Starovoitov]

0-day bot reported build error:
kernel/built-in.o: In function `map_lookup_elem':
>> kernel/bpf/.tmp_syscall.o:(.text+0x329b3c): undefined reference to `bpf_stackmap_copy'
when CONFIG_BPF_SYSCALL is set and CONFIG_PERF_EVENTS is not.
Add weak definition to resolve it.
This code path in map_lookup_elem() is never taken
when CONFIG_PERF_EVENTS is not set.

Fixes: 557c0c6e7df8 ("bpf: convert stackmap to pre-allocation")
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 kernel/bpf/syscall.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 2978d0d08869..2a2efe1bc76c 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -244,6 +244,11 @@ static void __user *u64_to_ptr(__u64 val)
 	return (void __user *) (unsigned long) val;
 }
 
+int __weak bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
+{
+	return -ENOTSUPP;
+}
+
 /* last field in 'union bpf_attr' used by this command */
 #define BPF_MAP_LOOKUP_ELEM_LAST_FIELD value
 
-- 
2.8.0.rc1

Re: [PATCH net-next] bpf: bpf_stackmap_copy depends on CONFIG_PERF_EVENTS

[David Miller]

From: Alexei Starovoitov <ast@fb.com>
Date: Wed, 9 Mar 2016 18:56:49 -0800

> 0-day bot reported build error:
> kernel/built-in.o: In function `map_lookup_elem':
>>> kernel/bpf/.tmp_syscall.o:(.text+0x329b3c): undefined reference to `bpf_stackmap_copy'
> when CONFIG_BPF_SYSCALL is set and CONFIG_PERF_EVENTS is not.
> Add weak definition to resolve it.
> This code path in map_lookup_elem() is never taken
> when CONFIG_PERF_EVENTS is not set.
> 
> Fixes: 557c0c6e7df8 ("bpf: convert stackmap to pre-allocation")
> Reported-by: Fengguang Wu <fengguang.wu@intel.com>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Applied.