From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
Masami Hiramatsu <mhiramat@kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [PATCH 5/7] powerpc/ftrace: Update ftrace_location() for powerpc -mprofile-kernel
Date: Tue, 18 Jun 2019 23:53:11 +0530 [thread overview]
Message-ID: <1560881840.vz9llflvnf.naveen@linux.ibm.com> (raw)
In-Reply-To: <1560881411.p0i6a1dkwk.naveen@linux.ibm.com>
Naveen N. Rao wrote:
> Steven Rostedt wrote:
>> On Tue, 18 Jun 2019 20:17:04 +0530
>> "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote:
>>
>>> @@ -1551,7 +1551,7 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end)
>>> key.flags = end; /* overload flags, as it is unsigned long */
>>>
>>> for (pg = ftrace_pages_start; pg; pg = pg->next) {
>>> - if (end < pg->records[0].ip ||
>>> + if (end <= pg->records[0].ip ||
>>
>> This breaks the algorithm. "end" is inclusive. That is, if you look for
>> a single byte, where "start" and "end" are the same, and it happens to
>> be the first ip on the pg page, it will be skipped, and not found.
>
> Thanks. It looks like I should be over-riding ftrace_location() instead.
> I will update this patch.
I think I will have ftrace own the two instruction range, regardless of
whether the preceding instruction is a 'mflr r0' or not. This simplifies
things and I don't see an issue with it as of now. I will do more
testing to confirm.
- Naveen
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/arch/powerpc/kernel/trace/ftrace.c
@@ -951,6 +951,16 @@ void arch_ftrace_update_code(int command)
}
#ifdef CONFIG_MPROFILE_KERNEL
+/*
+ * We consider two instructions -- 'mflr r0', 'bl _mcount' -- to be part
+ * of ftrace. When checking for the first instruction, we want to include
+ * the next instruction in the range check.
+ */
+unsigned long ftrace_location(unsigned long ip)
+{
+ return ftrace_location_range(ip, ip + MCOUNT_INSN_SIZE);
+}
+
/* Returns 1 if we patched in the mflr */
static int __ftrace_make_call_prep(struct dyn_ftrace *rec)
{
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 21d8e201ee80..122e2bb4a739 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1573,7 +1573,7 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end)
* the function tracer. It checks the ftrace internal tables to
* determine if the address belongs or not.
*/
-unsigned long ftrace_location(unsigned long ip)
+unsigned long __weak ftrace_location(unsigned long ip)
{
return ftrace_location_range(ip, ip);
}
next prev parent reply other threads:[~2019-06-18 18:23 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-18 14:46 [PATCH 0/7] powerpc/ftrace: Patch out -mprofile-kernel instructions Naveen N. Rao
2019-06-18 14:47 ` [PATCH 1/7] ftrace: Expose flags used for ftrace_replace_code() Naveen N. Rao
2019-06-18 14:47 ` [PATCH 2/7] x86/ftrace: Fix use of flags in ftrace_replace_code() Naveen N. Rao
2019-06-18 14:47 ` [PATCH 3/7] ftrace: Expose __ftrace_replace_code() Naveen N. Rao
2019-06-18 14:47 ` [PATCH 4/7] powerpc/ftrace: Additionally nop out the preceding mflr with -mprofile-kernel Naveen N. Rao
2019-06-19 5:14 ` Michael Ellerman
2019-06-19 7:10 ` Nicholas Piggin
2019-06-19 9:53 ` Naveen N. Rao
2019-06-19 10:41 ` Nicholas Piggin
2019-06-19 17:14 ` Naveen N. Rao
2019-06-18 14:47 ` [PATCH 5/7] powerpc/ftrace: Update ftrace_location() for powerpc -mprofile-kernel Naveen N. Rao
2019-06-18 15:45 ` Steven Rostedt
2019-06-18 18:11 ` Naveen N. Rao
2019-06-18 18:23 ` Naveen N. Rao [this message]
2019-06-18 18:32 ` Steven Rostedt
2019-06-19 7:56 ` Naveen N. Rao
2019-06-19 9:28 ` Steven Rostedt
2019-06-18 14:47 ` [PATCH 6/7] kprobes/ftrace: Use ftrace_location() when [dis]arming probes Naveen N. Rao
2019-06-21 14:41 ` Masami Hiramatsu
2019-06-18 14:47 ` [PATCH 7/7] powerpc/kprobes: Allow probing on any ftrace address Naveen N. Rao
2019-06-21 14:50 ` Masami Hiramatsu
2019-06-22 3:49 ` Joe Perches
2019-06-26 9:39 ` Naveen N. Rao
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1560881840.vz9llflvnf.naveen@linux.ibm.com \
--to=naveen.n.rao@linux.vnet.ibm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mhiramat@kernel.org \
--cc=mingo@kernel.org \
--cc=mpe@ellerman.id.au \
--cc=npiggin@gmail.com \
--cc=rostedt@goodmis.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).