From: Padmanabha Srinivasaiah <treasure4paddy@gmail.com>
To: jeyu@kernel.org, keescook@chromium.org, nathan@kernel.org,
ndesaulniers@google.com
Cc: samitolvanen@google.com, treasure4paddy@gmail.com,
Miroslav Benes <mbenes@suse.cz>,
Stephen Boyd <swboyd@chromium.org>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
Joe Perches <joe@perches.com>,
linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: [PATCH v3] kallsyms: strip CLANG CFI postfix ".cfi_jt"
Date: Thu, 29 Jul 2021 22:53:12 +0200 [thread overview]
Message-ID: <20210729205317.25685-1-treasure4paddy@gmail.com> (raw)
In-Reply-To: <CABCJKudYRiK0KcMHGHeBFcr+Smwa9EM+NFeBpMo_ePqK+zHz0w@mail.gmail.com>
Clang CFI adds a postfix ".cfi_jt" to a symbols of extern functions.
For example this breaks syscall tracer that doesn't expect such postfix,
so strip out the postfix from the expanded symbol.
Signed-off-by: Padmanabha Srinivasaiah <treasure4paddy@gmail.com>
---
Change in v3:
- Modified commit message to indicate fix is for Clang CFI postfix
- Rebased on recent patch from ndesaulniers@google.com.
- Fix is enabled even for CONFIG_LTO_CLANG
Change in v2:
- Use existing routine in kallsyms to strip postfix ".cfi_jt" from
extern function name.
- Modified the commit message accordingly
kernel/kallsyms.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 5cabe4dd3ff4..67d015854cbd 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -174,7 +174,8 @@ static bool cleanup_symbol_name(char *s)
* foo.llvm.974640843467629774. This can break hooking of static
* functions with kprobes.
*/
- if (!IS_ENABLED(CONFIG_LTO_CLANG_THIN))
+ if (!(IS_ENABLED(CONFIG_LTO_CLANG) ||
+ IS_ENABLED(CONFIG_LTO_CLANG_THIN)))
return false;
res = strstr(s, ".llvm.");
@@ -184,16 +185,24 @@ static bool cleanup_symbol_name(char *s)
}
/*
- * LLVM appends a hash to static function names when ThinLTO and CFI
- * are both enabled, i.e. foo() becomes
- * foo$707af9a22804d33c81801f27dcfe489b. This causes confusion and
- * potentially breaks user space tools, so we strip the suffix from
- * expanded symbol names.
+ * LLVM appends a hash to static function names when both
+ * (Thin/FULL) LTO and CFI are enabled, i.e. foo() becomes
+ * foo$707af9a22804d33c81801f27dcfe489b.
+ *
+ * In case of non static function symbol <funcsym>,
+ * the local jump table will have entry as <funcsym>.cfi_jt.
+ *
+ * This causes confusion and potentially breaks
+ * user space tools and some built-in components.
+ * So we strip the suffix from expanded symbol names.
*/
if (!IS_ENABLED(CONFIG_CFI_CLANG))
return false;
res = strrchr(s, '$');
+ if (!res)
+ res = strstr(s, ".cfi_jt");
+
if (res) {
*res = '\0';
return true;
--
2.17.1
next prev parent reply other threads:[~2021-07-29 20:54 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210727131853.GA18032@pswork>
2021-07-27 14:06 ` [PATCH v2] kallsyms: strip ThinLTO postfix ".cfi_jt" Padmanabha Srinivasaiah
2021-07-28 20:57 ` Sami Tolvanen
2021-07-29 15:29 ` Padmanabha Srinivasaiah
2021-07-29 20:53 ` Padmanabha Srinivasaiah [this message]
2021-08-03 16:28 ` [PATCH v3] kallsyms: strip CLANG CFI " Sami Tolvanen
2021-08-04 17:17 ` Padmanabha Srinivasaiah
2021-08-05 23:27 ` [PATCH v4] " Padmanabha Srinivasaiah
2021-08-12 23:05 ` Sami Tolvanen
2021-08-14 12:15 ` Padmanabha Srinivasaiah
2021-08-14 12:42 ` [PATCH v5] " Padmanabha Srinivasaiah
2021-10-01 18:29 ` Nick Desaulniers
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=20210729205317.25685-1-treasure4paddy@gmail.com \
--to=treasure4paddy@gmail.com \
--cc=clang-built-linux@googlegroups.com \
--cc=gustavoars@kernel.org \
--cc=jeyu@kernel.org \
--cc=joe@perches.com \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mbenes@suse.cz \
--cc=nathan@kernel.org \
--cc=ndesaulniers@google.com \
--cc=samitolvanen@google.com \
--cc=swboyd@chromium.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).