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Date: Sun, 27 Dec 2020 18:53:01 +0100
From: Charlotte Delenk <darkkirb@...kkirb.de>
To: musl@...ts.openwall.com
Subject: [PATCH] Add support for LLVM's Control Flow Integrity
Hi,
I have attempted to use musl HEAD together with clang's -fsanitize=cfi,
but currently it requires the main function to take all 3 arguments and
return an int.
After this patch is applied, clang will no longer try to add CFI
sanitization to the libc_start_main_stage2 function, allowing programs
to get to main().
I have tested CFI sanitization for both regular indirect functions
(qsort()) and thread creation and validly typed function pointers cause
no runtime aborts with CFI enabled for the whole program.
---
src/env/__libc_start_main.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/src/env/__libc_start_main.c b/src/env/__libc_start_main.c
index 8fbe5262..af61fb7c 100644
--- a/src/env/__libc_start_main.c
+++ b/src/env/__libc_start_main.c
@@ -85,6 +85,9 @@ int __libc_start_main(int (*main)(int,char **,char
**), int argc, char **argv)
return stage2(main, argc, argv);
}
+#ifdef __clang__
+__attribute__((no_sanitize("cfi")))
+#endif
static int libc_start_main_stage2(int (*main)(int,char **,char **),
int argc, char **argv)
{
char **envp = argv+argc+1;
--
2.29.2
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