linux-pci.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Sami Tolvanen <samitolvanen@google.com>
To: Kees Cook <keescook@chromium.org>
Cc: Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Will Deacon <will@kernel.org>, Jessica Yu <jeyu@kernel.org>,
	Arnd Bergmann <arnd@arndb.de>, Tejun Heo <tj@kernel.org>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	bpf@vger.kernel.org, linux-hardening@vger.kernel.org,
	linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kbuild@vger.kernel.org, linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Sami Tolvanen <samitolvanen@google.com>
Subject: [PATCH v2 07/17] kallsyms: strip ThinLTO hashes from static functions
Date: Thu, 18 Mar 2021 10:11:01 -0700	[thread overview]
Message-ID: <20210318171111.706303-8-samitolvanen@google.com> (raw)
In-Reply-To: <20210318171111.706303-1-samitolvanen@google.com>

With CONFIG_CFI_CLANG and ThinLTO, Clang appends a hash to the names
of all static functions not marked __used. This can break userspace
tools that don't expect the function name to change, so strip out the
hash from the output.

Suggested-by: Jack Pham <jackp@codeaurora.org>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 kernel/kallsyms.c | 54 ++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 49 insertions(+), 5 deletions(-)

diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 8043a90aa50e..17d3a704bafa 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -161,6 +161,26 @@ static unsigned long kallsyms_sym_address(int idx)
 	return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
 }
 
+#if defined(CONFIG_CFI_CLANG) && defined(CONFIG_LTO_CLANG_THIN)
+/*
+ * LLVM appends a hash to static function names when ThinLTO and CFI are
+ * both enabled, which causes confusion and potentially breaks user space
+ * tools, so we will strip the postfix from expanded symbol names.
+ */
+static inline char *cleanup_symbol_name(char *s)
+{
+	char *res = NULL;
+
+	res = strrchr(s, '$');
+	if (res)
+		*res = '\0';
+
+	return res;
+}
+#else
+static inline char *cleanup_symbol_name(char *s) { return NULL; }
+#endif
+
 /* Lookup the address for this symbol. Returns 0 if not found. */
 unsigned long kallsyms_lookup_name(const char *name)
 {
@@ -173,6 +193,9 @@ unsigned long kallsyms_lookup_name(const char *name)
 
 		if (strcmp(namebuf, name) == 0)
 			return kallsyms_sym_address(i);
+
+		if (cleanup_symbol_name(namebuf) && strcmp(namebuf, name) == 0)
+			return kallsyms_sym_address(i);
 	}
 	return module_kallsyms_lookup_name(name);
 }
@@ -303,7 +326,9 @@ const char *kallsyms_lookup(unsigned long addr,
 				       namebuf, KSYM_NAME_LEN);
 		if (modname)
 			*modname = NULL;
-		return namebuf;
+
+		ret = namebuf;
+		goto found;
 	}
 
 	/* See if it's in a module or a BPF JITed image. */
@@ -316,11 +341,16 @@ const char *kallsyms_lookup(unsigned long addr,
 	if (!ret)
 		ret = ftrace_mod_address_lookup(addr, symbolsize,
 						offset, modname, namebuf);
+
+found:
+	cleanup_symbol_name(namebuf);
 	return ret;
 }
 
 int lookup_symbol_name(unsigned long addr, char *symname)
 {
+	int res;
+
 	symname[0] = '\0';
 	symname[KSYM_NAME_LEN - 1] = '\0';
 
@@ -331,15 +361,23 @@ int lookup_symbol_name(unsigned long addr, char *symname)
 		/* Grab name */
 		kallsyms_expand_symbol(get_symbol_offset(pos),
 				       symname, KSYM_NAME_LEN);
-		return 0;
+		goto found;
 	}
 	/* See if it's in a module. */
-	return lookup_module_symbol_name(addr, symname);
+	res = lookup_module_symbol_name(addr, symname);
+	if (res)
+		return res;
+
+found:
+	cleanup_symbol_name(symname);
+	return 0;
 }
 
 int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
 			unsigned long *offset, char *modname, char *name)
 {
+	int res;
+
 	name[0] = '\0';
 	name[KSYM_NAME_LEN - 1] = '\0';
 
@@ -351,10 +389,16 @@ int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
 		kallsyms_expand_symbol(get_symbol_offset(pos),
 				       name, KSYM_NAME_LEN);
 		modname[0] = '\0';
-		return 0;
+		goto found;
 	}
 	/* See if it's in a module. */
-	return lookup_module_symbol_attrs(addr, size, offset, modname, name);
+	res = lookup_module_symbol_attrs(addr, size, offset, modname, name);
+	if (res)
+		return res;
+
+found:
+	cleanup_symbol_name(name);
+	return 0;
 }
 
 /* Look up a kernel symbol and return it in a text buffer. */
-- 
2.31.0.291.g576ba9dcdaf-goog


  parent reply	other threads:[~2021-03-18 17:12 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-18 17:10 [PATCH v2 00/17] Add support for Clang CFI Sami Tolvanen
2021-03-18 17:10 ` [PATCH v2 01/17] add " Sami Tolvanen
2021-03-18 22:29   ` Peter Zijlstra
2021-03-18 23:48     ` Sami Tolvanen
2021-03-19 12:26       ` Peter Zijlstra
2021-03-19 13:52         ` Paul E. McKenney
2021-03-19 16:17           ` Sami Tolvanen
2021-03-19 17:03             ` Paul E. McKenney
2021-03-18 17:10 ` [PATCH v2 02/17] cfi: add __cficanonical Sami Tolvanen
2021-03-18 17:49   ` Nick Desaulniers
2021-03-18 17:10 ` [PATCH v2 03/17] mm: add generic __va_function and __pa_function macros Sami Tolvanen
2021-03-18 17:10 ` [PATCH v2 04/17] module: ensure __cfi_check alignment Sami Tolvanen
2021-03-18 19:27   ` Nick Desaulniers
2021-03-18 21:43     ` Sami Tolvanen
2021-03-18 17:10 ` [PATCH v2 05/17] workqueue: use WARN_ON_FUNCTION_MISMATCH Sami Tolvanen
2021-03-18 18:50   ` Nick Desaulniers
2021-03-18 21:38     ` Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 06/17] kthread: " Sami Tolvanen
2021-03-18 17:11 ` Sami Tolvanen [this message]
2021-03-18 19:00   ` [PATCH v2 07/17] kallsyms: strip ThinLTO hashes from static functions Nick Desaulniers
2021-03-18 21:41     ` Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 08/17] bpf: disable CFI in dispatcher functions Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 09/17] lib/list_sort: fix function type mismatches Sami Tolvanen
2021-03-18 18:31   ` Nick Desaulniers
2021-03-18 21:31     ` Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 10/17] lkdtm: use __va_function Sami Tolvanen
2021-03-18 18:43   ` Nick Desaulniers
2021-03-18 18:45     ` Nick Desaulniers
2021-03-18 17:11 ` [PATCH v2 11/17] psci: use __pa_function for cpu_resume Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 12/17] arm64: implement __va_function Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 13/17] arm64: use __pa_function Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 14/17] arm64: add __nocfi to functions that jump to a physical address Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 15/17] arm64: add __nocfi to __apply_alternatives Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 16/17] KVM: arm64: Disable CFI for nVHE Sami Tolvanen
2021-03-18 17:11 ` [PATCH v2 17/17] arm64: allow CONFIG_CFI_CLANG to be selected Sami Tolvanen

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=20210318171111.706303-8-samitolvanen@google.com \
    --to=samitolvanen@google.com \
    --cc=arnd@arndb.de \
    --cc=bpf@vger.kernel.org \
    --cc=hch@infradead.org \
    --cc=jeyu@kernel.org \
    --cc=keescook@chromium.org \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-hardening@vger.kernel.org \
    --cc=linux-kbuild@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-pci@vger.kernel.org \
    --cc=masahiroy@kernel.org \
    --cc=nathan@kernel.org \
    --cc=ndesaulniers@google.com \
    --cc=paulmck@kernel.org \
    --cc=tj@kernel.org \
    --cc=will@kernel.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).