On 3/27/18 5:44 PM, Mathieu Desnoyers wrote:
----- On Mar 27, 2018, at 8:00 PM, Alexei Starovoitov ast@xxxxxx wrote:
On 3/27/18 4:13 PM, Mathieu Desnoyers wrote:
----- On Mar 27, 2018, at 6:48 PM, Alexei Starovoitov ast@xxxxxx wrote:
On 3/27/18 2:04 PM, Steven Rostedt wrote:
+#ifdef CONFIG_BPF_EVENTS
+#define BPF_RAW_TP() . = ALIGN(8); \
Given that the section consists of a 16-bytes structure elements
on architectures with 8 bytes pointers, this ". = ALIGN(8)" should
be turned into a STRUCT_ALIGN(), especially given that the compiler
is free to up-align the structure on 32 bytes.
STRUCT_ALIGN fixed the 'off by 8' issue with kasan,
but it fails without kasan too.
For some reason the whole region __start__bpf_raw_tp - __stop__bpf_raw_tp
comes inited with cccc:
[ 22.703562] i 1 btp ffffffff8288e530 btp->tp cccccccccccccccc func
cccccccccccccccc
[ 22.704638] i 2 btp ffffffff8288e540 btp->tp cccccccccccccccc func
cccccccccccccccc
[ 22.705599] i 3 btp ffffffff8288e550 btp->tp cccccccccccccccc func
cccccccccccccccc
[ 22.706551] i 4 btp ffffffff8288e560 btp->tp cccccccccccccccc func
cccccccccccccccc
[ 22.707503] i 5 btp ffffffff8288e570 btp->tp cccccccccccccccc func
cccccccccccccccc
[ 22.708452] i 6 btp ffffffff8288e580 btp->tp cccccccccccccccc func
cccccccccccccccc
[ 22.709406] i 7 btp ffffffff8288e590 btp->tp cccccccccccccccc func
cccccccccccccccc
[ 22.710368] i 8 btp ffffffff8288e5a0 btp->tp cccccccccccccccc func
cccccccccccccccc
while gdb shows that everything is good inside vmlinux
for exactly these addresses.
Some other linker magic missing?
No, Steven's iteration code is incorrect.
+extern struct bpf_raw_event_map __start__bpf_raw_tp;
+extern struct bpf_raw_event_map __stop__bpf_raw_tp;
That should be:
extern struct bpf_raw_event_map __start__bpf_raw_tp[];
extern struct bpf_raw_event_map __stop__bpf_raw_tp[];
+
+struct bpf_raw_event_map *bpf_find_raw_tracepoint(const char *name)
+{
+ const struct bpf_raw_event_map *btp = &__start__bpf_raw_tp;
const struct bpf_raw_event_map *btp = __start__bpf_raw_tp;
+ int i = 0;
+
+ for (; btp < &__stop__bpf_raw_tp; btp++) {
for (; btp < __stop__bpf_raw_tp; btp++) {
Those start/stop symbols are given their address by the linker
automatically (this is a GNU linker extension). We don't want
pointers to the symbols, but rather the symbols per se to act
as start/stop addresses.
right. that part I fixed first.
Turned out it was in init.data section and got poisoned.
this fixes it:
@@ -258,6 +258,7 @@
LIKELY_PROFILE() \
BRANCH_PROFILE() \
TRACE_PRINTKS() \
+ BPF_RAW_TP() \
TRACEPOINT_STR()
/*
@@ -585,7 +586,6 @@
*(.init.rodata) \
FTRACE_EVENTS() \
TRACE_SYSCALLS() \
- BPF_RAW_TP() \
KPROBE_BLACKLIST() \
ERROR_INJECT_WHITELIST() \
MEM_DISCARD(init.rodata) \
and it works :)
I will clean few other nits I found while debugging and respin.
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