LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Nick Desaulniers <ndesaulniers@google.com>
To: Kees Cook <keescook@chromium.org>
Cc: Fangrui Song <maskray@google.com>,
	Nick Desaulniers <ndesaulniers@google.com>,
	"KE . LI" <like1@oppo.com>, Nathan Chancellor <nathan@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Miguel Ojeda <ojeda@kernel.org>, Joe Perches <joe@perches.com>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	Sami Tolvanen <samitolvanen@google.com>,
	Stephen Boyd <swboyd@chromium.org>,
	linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: [PATCH v3] kallsyms: strip LTO suffixes from static functions
Date: Mon, 28 Jun 2021 13:31:06 -0700	[thread overview]
Message-ID: <20210628203109.2501792-1-ndesaulniers@google.com> (raw)
In-Reply-To: <a970613b-014f-be76-e342-4a51e792b56d@kernel.org>

Similar to:
commit 8b8e6b5d3b01 ("kallsyms: strip ThinLTO hashes from static
functions")

It's very common for compilers to modify the symbol name for static
functions as part of optimizing transformations. That makes hooking
static functions (that weren't inlined or DCE'd) with kprobes difficult.

LLVM has yet another name mangling scheme used by thin LTO.  Strip off
these suffixes so that we can continue to hook such static functions.

Reported-by: KE.LI(Lieke) <like1@oppo.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
Changes v2 -> V3:
* Un-nest preprocessor checks, as per Nathan.

Changes v1 -> v2:
* Both mangling schemes can occur for thinLTO + CFI, this new scheme can
  also occur for thinLTO without CFI. Split cleanup_symbol_name() into
  two function calls.
* Drop KE.LI's tested by tag.
* Do not carry Fangrui's Reviewed by tag.
* Drop the inline keyword; it is meaningless.
 kernel/kallsyms.c | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 4067564ec59f..143c69e7e75d 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -171,6 +171,26 @@ static unsigned long kallsyms_sym_address(int idx)
 	return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
 }
 
+#ifdef CONFIG_LTO_CLANG_THIN
+/*
+ * LLVM appends a suffix for local variables that must be promoted to global
+ * scope as part of thin LTO. foo() becomes foo.llvm.974640843467629774. This
+ * can break hooking of static functions with kprobes.
+ */
+static bool cleanup_symbol_name_thinlto(char *s)
+{
+	char *res;
+
+	res = strstr(s, ".llvm.");
+	if (res)
+		*res = '\0';
+
+	return res != NULL;
+}
+#else
+static bool cleanup_symbol_name_thinlto(char *s) { return false; }
+#endif /* CONFIG_LTO_CLANG_THIN */
+
 #if defined(CONFIG_CFI_CLANG) && defined(CONFIG_LTO_CLANG_THIN)
 /*
  * LLVM appends a hash to static function names when ThinLTO and CFI are
@@ -178,7 +198,7 @@ static unsigned long kallsyms_sym_address(int idx)
  * This causes confusion and potentially breaks user space tools, so we
  * strip the suffix from expanded symbol names.
  */
-static inline bool cleanup_symbol_name(char *s)
+static bool cleanup_symbol_name_thinlto_cfi(char *s)
 {
 	char *res;
 
@@ -189,8 +209,14 @@ static inline bool cleanup_symbol_name(char *s)
 	return res != NULL;
 }
 #else
-static inline bool cleanup_symbol_name(char *s) { return false; }
-#endif
+static bool cleanup_symbol_name_thinlto_cfi(char *s) { return false; }
+#endif /* CONFIG_CFI_CLANG && CONFIG_LTO_CLANG_THIN */
+
+static bool cleanup_symbol_name(char *s)
+{
+	return cleanup_symbol_name_thinlto(s) &&
+		cleanup_symbol_name_thinlto_cfi(s);
+}
 
 /* Lookup the address for this symbol. Returns 0 if not found. */
 unsigned long kallsyms_lookup_name(const char *name)
-- 
2.32.0.93.g670b81a890-goog


  reply	other threads:[~2021-06-28 20:31 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-22 18:38 [PATCH] " Nick Desaulniers
2021-06-22 20:18 ` Fangrui Song
2021-06-28 17:54   ` Nick Desaulniers
2021-06-28 18:20     ` Nick Desaulniers
2021-06-28 19:05   ` [PATCH v2] " Nick Desaulniers
2021-06-28 19:45     ` Nathan Chancellor
2021-06-28 20:31       ` Nick Desaulniers [this message]
2021-06-28 21:19         ` [PATCH v3] " Nathan Chancellor
2021-06-28 22:01           ` Nick Desaulniers
2021-06-28 22:16             ` Nathan Chancellor
2021-07-07 18:18               ` [PATCH v4] " Nick Desaulniers
2021-07-07 18:34                 ` Nathan Chancellor
2021-07-07 18:59                   ` Fāng-ruì Sòng
2021-08-06 16:20                 ` Sami Tolvanen
2021-10-01 19:58                   ` [PATCH v5] " Nick Desaulniers
2021-10-01 20:05                     ` Sami Tolvanen
2021-10-04 10:46                       ` 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=20210628203109.2501792-1-ndesaulniers@google.com \
    --to=ndesaulniers@google.com \
    --cc=akpm@linux-foundation.org \
    --cc=clang-built-linux@googlegroups.com \
    --cc=gustavoars@kernel.org \
    --cc=joe@perches.com \
    --cc=keescook@chromium.org \
    --cc=like1@oppo.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=maskray@google.com \
    --cc=nathan@kernel.org \
    --cc=ojeda@kernel.org \
    --cc=rdunlap@infradead.org \
    --cc=samitolvanen@google.com \
    --cc=sfr@canb.auug.org.au \
    --cc=swboyd@chromium.org \
    --subject='Re: [PATCH v3] kallsyms: strip LTO suffixes from static functions' \
    /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).