gcc-plugins: arm_ssp_per_task_plugin: sign extend the SP mask

The ARM per-task stack protector GCC plugin hits an assert in
the compiler in some case, due to the fact the the SP mask
expression is not sign-extended as it should be. So fix that.

Suggested-by: Kugan Vivekanandarajah <kugan.vivekanandarajah@linaro.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Kees Cook <keescook@chromium.org>

diff --git a/scripts/gcc-plugins/arm_ssp_per_task_plugin.c b/scripts/gcc-plugins/arm_ssp_per_task_plugin.c
index de70b8470971e8929a5949174c48a84ab774e0b7..a65fbefb85019f402290abde571d59bc41d99a89 100644 (file)
--- a/scripts/gcc-plugins/arm_ssp_per_task_plugin.c
+++ b/scripts/gcc-plugins/arm_ssp_per_task_plugin.c
@@ -13,7 +13,7 @@ static unsigned int arm_pertask_ssp_rtl_execute(void)
        for (insn = get_insns(); insn; insn = NEXT_INSN(insn)) {
                const char *sym;
                rtx body;
-               rtx masked_sp;
+               rtx mask, masked_sp;
 
                /*
                 * Find a SET insn involving a SYMBOL_REF to __stack_chk_guard
@@ -33,12 +33,13 @@ static unsigned int arm_pertask_ssp_rtl_execute(void)
                 * produces the address of the copy of the stack canary value
                 * stored in struct thread_info
                 */
+               mask = GEN_INT(sext_hwi(sp_mask, GET_MODE_PRECISION(Pmode)));
                masked_sp = gen_reg_rtx(Pmode);
 
                emit_insn_before(gen_rtx_SET(masked_sp,
                                             gen_rtx_AND(Pmode,
                                                         stack_pointer_rtx,
-                                                        GEN_INT(sp_mask))),
+                                                        mask)),
                                 insn);
 
                SET_SRC(body) = gen_rtx_PLUS(Pmode, masked_sp,