lkml.org 
[lkml]   [2022]   [Aug]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 1/3] x86/ibt, objtool: Add IBT_NOSEAL()
Date
Add a macro which prevents a function from getting sealed if there are
no compile-time references to it.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
arch/x86/include/asm/ibt.h | 10 ++++++++++
tools/objtool/check.c | 3 ++-
2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/ibt.h b/arch/x86/include/asm/ibt.h
index 689880eca9ba..372e8eee6e02 100644
--- a/arch/x86/include/asm/ibt.h
+++ b/arch/x86/include/asm/ibt.h
@@ -31,6 +31,16 @@

#define __noendbr __attribute__((nocf_check))

+/*
+ * Create a dummy function pointer reference to prevent objtool from marking
+ * the function as needing to be "sealed" (i.e. ENDBR converted to NOP by
+ * apply_ibt_endbr()).
+ */
+#define IBT_NOSEAL(fname) \
+ ".pushsection .discard.ibt_endbr_noseal\n\t" \
+ _ASM_PTR fname "\n\t" \
+ ".popsection\n\t"
+
static inline __attribute_const__ u32 gen_endbr(void)
{
u32 endbr;
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 0cec74da7ffe..91678252a9b6 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4096,7 +4096,8 @@ static int validate_ibt(struct objtool_file *file)
* These sections can reference text addresses, but not with
* the intent to indirect branch to them.
*/
- if (!strncmp(sec->name, ".discard", 8) ||
+ if ((!strncmp(sec->name, ".discard", 8) &&
+ strcmp(sec->name, ".discard.ibt_endbr_noseal")) ||
!strncmp(sec->name, ".debug", 6) ||
!strcmp(sec->name, ".altinstructions") ||
!strcmp(sec->name, ".ibt_endbr_seal") ||
--
2.37.2
\
 
 \ /
  Last update: 2022-08-18 18:15    [W:0.309 / U:0.060 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site