From c905a3680dc1dae044ea6b9aaf9f0482e5ebf63c Mon Sep 17 00:00:00 2001 From: Daniele Buono Date: Fri, 4 Dec 2020 18:06:12 -0500 Subject: cfi: Initial support for cfi-icall in QEMU MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit LLVM/Clang, supports runtime checks for forward-edge Control-Flow Integrity (CFI). CFI on indirect function calls (cfi-icall) ensures that, in indirect function calls, the function called is of the right signature for the pointer type defined at compile time. For this check to work, the code must always respect the function signature when using function pointer, the function must be defined at compile time, and be compiled with link-time optimization. This rules out, for example, shared libraries that are dynamically loaded (given that functions are not known at compile time), and code that is dynamically generated at run-time. This patch: 1) Introduces the CONFIG_CFI flag to support cfi in QEMU 2) Introduces a decorator to allow the definition of "sensitive" functions, where a non-instrumented function may be called at runtime through a pointer. The decorator will take care of disabling cfi-icall checks on such functions, when cfi is enabled. 3) Marks functions currently in QEMU that exhibit such behavior, in particular: - The function in TCG that calls pre-compiled TBs - The function in TCI that interprets instructions - Functions in the plugin infrastructures that jump to callbacks - Functions in util that directly call a signal handler Signed-off-by: Daniele Buono Acked-by: Alex Bennée Signed-off-by: Paolo Bonzini --- plugins/loader.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'plugins/loader.c') diff --git a/plugins/loader.c b/plugins/loader.c index 5cb9794fda..8550e61184 100644 --- a/plugins/loader.c +++ b/plugins/loader.c @@ -32,6 +32,7 @@ #ifndef CONFIG_USER_ONLY #include "hw/boards.h" #endif +#include "qemu/compiler.h" #include "plugin.h" @@ -150,6 +151,12 @@ static uint64_t xorshift64star(uint64_t x) return x * UINT64_C(2685821657736338717); } +/* + * Disable CFI checks. + * The install and version functions have been loaded from an external library + * so we do not have type information + */ +QEMU_DISABLE_CFI static int plugin_load(struct qemu_plugin_desc *desc, const qemu_info_t *info, Error **errp) { qemu_plugin_install_func_t install; -- cgit v1.2.3