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Fri, 10 Jun 2022 16:35:32 -0700 (PDT) Date: Fri, 10 Jun 2022 16:35:00 -0700 In-Reply-To: <20220610233513.1798771-1-samitolvanen@google.com> Message-Id: <20220610233513.1798771-8-samitolvanen@google.com> Mime-Version: 1.0 References: <20220610233513.1798771-1-samitolvanen@google.com> X-Developer-Key: i=samitolvanen@google.com; a=openpgp; fpr=35CCFB63B283D6D3AEB783944CB5F6848BBC56EE X-Developer-Signature: v=1; a=openpgp-sha256; l=1572; h=from:subject; bh=jl9DoMc+4oRrqZLAq39OlbrQ/0d/T8NfhRiPohw7q0M=; b=owEB7QES/pANAwAKAUy19oSLvFbuAcsmYgBio9Ut8FBG9LlQYcuQASRpKpCEiZFqDFuo2OISqNmD PZHD7ayJAbMEAAEKAB0WIQQ1zPtjsoPW0663g5RMtfaEi7xW7gUCYqPVLQAKCRBMtfaEi7xW7htGC/ 9S64HtVNUNx8wUV9jEnq0eOMIRwIfRD2KvOlklON0r7+HT+G3Pc3gUkJCk10zTrCdF9O6RvedaSLQ1 /APpiaRGnwUDzGRmTSr52h8ENGvOZT91UiUJS4Yw2DGcde7NhGS1BuoTLxP4l7z6QKu5QRjQ6iMvbf NRG2A7T8qWteCX3yLVRGQqSwq3usqGFdb+pXAaSjumRGoRftE0xL3ac+4NC4xX+mH3548juVL43+Cw aHMxz7BmXUffA7onVHE1txP0Zgg0LFxpupHSuoUepfjBuWucPFc8S1ocJKoFoJSSV6pVwHkap5ABEO BWbEeGFkI/kwG2N6kjEIsvWU7SYxiBwkY6ZrU6SY0yr1QlEnSuIYgeihNeV/eezgPXpmEmLA3K2rOs k77a1zmGXN/DmKK0/SQ6tnXd8KBpEf1y+W+5D/S3Oxxc/2zfRRBUshgafKlNTufhcex9IWhrCQmgVo INo3nzmG8TKawDTcvMlv4YBLBK3gqIeVjCwmORqhDtl9Y= X-Mailer: git-send-email 2.36.1.476.g0c4daa206d-goog Subject: [RFC PATCH v3 07/20] lkdtm: Emit an indirect call for CFI tests From: Sami Tolvanen To: linux-kernel@vger.kernel.org Cc: Kees Cook , Josh Poimboeuf , Peter Zijlstra , x86@kernel.org, Catalin Marinas , Will Deacon , Mark Rutland , Nathan Chancellor , Nick Desaulniers , Joao Moreira , Sedat Dilek , Steven Rostedt , linux-hardening@vger.kernel.org, linux-arm-kernel@lists.infradead.org, llvm@lists.linux.dev, Sami Tolvanen Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-9.6 required=5.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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 666a7f4bc137..b6b375112a2a 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); -- 2.36.1.476.g0c4daa206d-goog