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bpf: add a bpf_override_function helper

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Error injection is sloppy and very ad-hoc.  BPF could fill this niche
perfectly with it's kprobe functionality.  We could make sure errors are
only triggered in specific call chains that we care about with very
specific situations.  Accomplish this with the bpf_override_funciton
helper.  This will modify the probe'd callers return value to the
specified value and set the PC to an override function that simply
returns, bypassing the originally probed function.  This gives us a nice
clean way to implement systematic error injection for all of our code
paths.

Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Josef Bacik
2017-12-11 11:36:48 -05:00
committed by Alexei Starovoitov
parent 8556e50994
commit 9802d86585
15 changed files with 154 additions and 9 deletions
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12
kernel/trace/trace_probe.h
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@@ -252,6 +252,8 @@ struct symbol_cache;
unsigned long update_symbol_cache(struct symbol_cache *sc);
void free_symbol_cache(struct symbol_cache *sc);
struct symbol_cache *alloc_symbol_cache(const char *sym, long offset);
int trace_kprobe_ftrace(struct trace_event_call *call);
int trace_kprobe_error_injectable(struct trace_event_call *call);
#else
/* uprobes do not support symbol fetch methods */
#define fetch_symbol_u8 NULL
@@ -277,6 +279,16 @@ alloc_symbol_cache(const char *sym, long offset)
{
return NULL;
}
static inline int trace_kprobe_ftrace(struct trace_event_call *call)
{
return 0;
}
static inline int trace_kprobe_error_injectable(struct trace_event_call *call)
{
return 0;
}
#endif /* CONFIG_KPROBE_EVENTS */
struct probe_arg {