linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
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


  parent reply	other threads:[~2021-07-29 20:54 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20210727131853.GA18032@pswork>
2021-07-27 14:06 ` [PATCH v2] kallsyms: strip ThinLTO " 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

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 \
    --subject='Re: [PATCH v3] kallsyms: strip CLANG CFI postfix ".cfi_jt"' \
    /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

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox