Messages in this thread Patch in this message | | | Date | Tue, 30 Aug 2022 16:31:15 -0700 | Subject | [PATCH v4 07/21] lkdtm: Emit an indirect call for CFI tests | From | Sami Tolvanen <> |
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Clang can convert the indirect calls in lkdtm_CFI_FORWARD_PROTO into direct calls. Move the call into a noinline function that accepts the target address as an argument to ensure the compiler actually emits an indirect call instead.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Acked-by: Kees Cook <keescook@chromium.org> --- drivers/misc/lkdtm/cfi.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/drivers/misc/lkdtm/cfi.c b/drivers/misc/lkdtm/cfi.c index 71483cb1e422..5245cf6013c9 100644 --- a/drivers/misc/lkdtm/cfi.c +++ b/drivers/misc/lkdtm/cfi.c @@ -20,6 +20,13 @@ static noinline int lkdtm_increment_int(int *counter) return *counter; } + +/* Don't allow the compiler to inline the calls. */ +static noinline void lkdtm_indirect_call(void (*func)(int *)) +{ + func(&called_count); +} + /* * This tries to call an indirect function with a mismatched prototype. */ @@ -29,15 +36,11 @@ static void lkdtm_CFI_FORWARD_PROTO(void) * Matches lkdtm_increment_void()'s prototype, but not * lkdtm_increment_int()'s prototype. */ - void (*func)(int *); - pr_info("Calling matched prototype ...\n"); - func = lkdtm_increment_void; - func(&called_count); + lkdtm_indirect_call(lkdtm_increment_void); pr_info("Calling mismatched prototype ...\n"); - func = (void *)lkdtm_increment_int; - func(&called_count); + lkdtm_indirect_call((void *)lkdtm_increment_int); pr_err("FAIL: survived mismatched prototype function call!\n"); pr_expected_config(CONFIG_CFI_CLANG); -- 2.37.2.672.g94769d06f0-goog
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