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perf-probe: Add user memory access attribute support

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Add user memory access attribute for kprobe event arguments.
If a given 'local variable' is in user-space, User can
specify memory access method by '@user' suffix. This is
not only for string but also for data structure.

If we access a field of data structure in user memory from
kernel on some arch, it will fail. e.g.

 perf probe -a "sched_setscheduler param->sched_priority"

This will fail to access the "param->sched_priority" because
the param is __user pointer. Instead, we can now specify
@user suffix for such argument.

 perf probe -a "sched_setscheduler param->sched_priority@user"

Note that kernel memory access with "@user" must always fail
on any arch.

Link: http://lkml.kernel.org/r/155789874562.26965.10836126971405890891.stgit@devnote2

Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Masami Hiramatsu
2019-05-15 14:39:05 +09:00
committed by Steven Rostedt (VMware)
parent bdf2b8cbf0
commit 1e032f7cfa
6 changed files with 35 additions and 8 deletions
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11
tools/perf/util/probe-event.c
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@@ -1577,6 +1577,17 @@ static int parse_perf_probe_arg(char *str, struct perf_probe_arg *arg)
str = tmp + 1;
}
tmp = strchr(str, '@');
if (tmp && tmp != str && strcmp(tmp + 1, "user")) { /* user attr */
if (!user_access_is_supported()) {
semantic_error("ftrace does not support user access\n");
return -EINVAL;
}
*tmp = '\0';
arg->user_access = true;
pr_debug("user_access ");
}
tmp = strchr(str, ':');
if (tmp) { /* Type setting */
*tmp = '\0';