This patch enables ftrace_location() to be used before ftrace_init().
The first user should be early kprobes, which can insert kprobes to
kernel code even before setup_arch() finishes. This patch gives it a
chance to determine whether it is probing ftrace entries and allows it
do some special treatment.
ftrace_cmp_ips_insn() is introduced to make early ftrace_location()
behavior consistent with normal ftrace_location(). With existing
ftrace_cmp_ips(), searching an address in middle of an instruction will
fail, which is inconsistent with ftrace_cmp_recs() used by normal
ftrace_location().
With this and previous patch ftrace_location() now is able to be called
in and after setup_arch().
Signed-off-by: Wang Nan <wangn...@huawei.com>
---
kernel/trace/ftrace.c | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index fa3cdd3..7fa88d0 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1539,6 +1539,8 @@ static unsigned long ftrace_location_range(unsigned long
start, unsigned long en
return 0;
}
+static unsigned long ftrace_search_mcount_ip(unsigned long ip);
+
/**
* ftrace_location - return true if the ip giving is a traced location
* @ip: the instruction pointer to check
@@ -1550,6 +1552,9 @@ static unsigned long ftrace_location_range(unsigned long
start, unsigned long en
*/
unsigned long ftrace_location(unsigned long ip)
{
+ if (unlikely(!ftrace_pages_start))
+ return ftrace_search_mcount_ip(ip);
+
return ftrace_location_range(ip, ip);
}
@@ -4733,6 +4738,18 @@ static int ftrace_cmp_ips(const void *a, const void *b)
return 0;
}
+static int ftrace_cmp_ips_insn(const void *a, const void *b)
+{
+ const unsigned long *ipa = a;
+ const unsigned long *ipb = b;
+
+ if (*ipa >= *ipb + MCOUNT_INSN_SIZE)
+ return 1;
+ if (*ipa < *ipb)
+ return -1;
+ return 0;
+}
+
static void ftrace_swap_ips(void *a, void *b, int size)
{
unsigned long *ipa = a;
@@ -4770,6 +4787,27 @@ static void ftrace_sort_mcount_area(unsigned long
*start, unsigned long *end)
kernel_mcount_sorted = true;
}
+static unsigned long ftrace_search_mcount_ip(unsigned long ip)
+{
+ extern unsigned long __start_mcount_loc[];
+ extern unsigned long __stop_mcount_loc[];
+
+ unsigned long *mcount_start = __start_mcount_loc;
+ unsigned long *mcount_end = __stop_mcount_loc;
+ unsigned long count = mcount_end - mcount_start;
+ unsigned long *retval;
+
+ if (!kernel_mcount_sorted)
+ return 0;
+
+ retval = bsearch(&ip, mcount_start, count,
+ sizeof(unsigned long), ftrace_cmp_ips_insn);
+ if (!retval)
+ return 0;
+
+ return ftrace_call_adjust(ip);
+}
+
static int ftrace_process_locs(struct module *mod,
unsigned long *start,
unsigned long *end)
--
1.8.4
--
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