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, samitolvanen@google.com
Cc: treasure4paddy@gmail.com, Miroslav Benes <mbenes@suse.cz>,
	Stephen Boyd <swboyd@chromium.org>, Joe Perches <joe@perches.com>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
	linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: [PATCH v5] kallsyms: strip CLANG CFI postfix ".cfi_jt"
Date: Sat, 14 Aug 2021 14:42:19 +0200	[thread overview]
Message-ID: <20210814124224.8551-1-treasure4paddy@gmail.com> (raw)
In-Reply-To: <CABCJKue6dYBYTJtyX6oE8Lq1LVHcS+vq+Z4cRE2-Tut8GRHjPQ@mail.gmail.com>

Clang CFI adds a postfix ".cfi_jt" to a symbols of extern functions.
For e.g. 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 v5:
  - Also remove explcit config check for postfix ".llvm." as LLVM
    renames even in full LTO case

Change in v4:
  - Remove redundant check; irrespective of LTO type (THIN/FULL),
    LTO_CLANG will be always enabled. Hence will be used as entry flag
    to check various postfix patterns.
  - And prior to stripping postfix ".cfi_jt", added a comment to
    justify why we are doing so.
 
Change in v3:
  - Modified commit message to indicate fix is for Clang CFI postfix
  - Rebased on recent patch from ndesaulniers@google.com.
    https://lore.kernel.org/lkml/
	20210707181814.365496-1-ndesaulniers@google.com/#t
  - 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 | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 5cabe4dd3ff4..c8ef618e2a71 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -174,7 +174,7 @@ 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))
 		return false;
 
 	res = strstr(s, ".llvm.");
@@ -194,6 +194,17 @@ static bool cleanup_symbol_name(char *s)
 		return false;
 
 	res = strrchr(s, '$');
+	if (!res) {
+		/*
+		 * In case of non static function symbol <funcsym>,
+		 * the local jump table will have entry as <funcsym>.cfi_jt.
+		 *
+		 * Such expansion breaks some built-in components,
+		 * e.g. syscall tracer. Hence remove postfix ".cfi_jt".
+		 */
+		res = strstr(s, ".cfi_jt");
+	}
+
 	if (res) {
 		*res = '\0';
 		return true;
-- 
2.17.1


  parent reply	other threads:[~2021-08-14 12:43 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 " Padmanabha Srinivasaiah
2021-07-28 20:57   ` Sami Tolvanen
2021-07-29 15:29     ` Padmanabha Srinivasaiah
2021-07-29 20:53     ` [PATCH v3] kallsyms: strip CLANG CFI " Padmanabha Srinivasaiah
2021-08-03 16:28       ` 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             ` Padmanabha Srinivasaiah [this message]
2021-10-01 18:29               ` [PATCH v5] " 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=20210814124224.8551-1-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 v5] 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
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).