From 656a9664bf828fc19b1e5a6e982bbcad456d1092 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?R=C3=A9mi=20Denis-Courmont?= Date: Mon, 29 Jul 2024 22:33:16 +0300 Subject: [PATCH] checkasm/riscv: preserve T1 whilst calling... This preserves T1 whilst calling the instrumented function. In a Sci-Fi setting where type-based Control Flow Integrity (CFI) is supported, the calling code (i.e., the `checkasm` test case) will set T1 to the expected value of the landing pad label (LPL) of the instrumented function. The call wrapper will always use LPL zero which is a wild card. We should preserve the value of T1 at least until the indirect call to the instrumented function. Of course this is Sci-Fi, because: 1) there is no hardware (or even QEMU) support yet, 2) all our assembler functions currently use LPL zero anyway. This uses T3 rather than T2 because indirect branches with T2 is reserved for notionally direct calls made with an indirect call instruction (e.g. due to GOT indirection), and are exempted from forward-edge CFI checks. --- tests/checkasm/riscv/checkasm.S | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/tests/checkasm/riscv/checkasm.S b/tests/checkasm/riscv/checkasm.S index e8bcbb271e..c4b034ae23 100644 --- a/tests/checkasm/riscv/checkasm.S +++ b/tests/checkasm/riscv/checkasm.S @@ -89,8 +89,8 @@ func checkasm_get_wrapper, v /* Clobber the vector configuration */ li t0, 0 /* Vector length: zero */ - li t1, -1 << 31 /* Vector type: illegal */ - vsetvl zero, t0, t1 + li t2, -4 /* Vector type: illegal */ + vsetvl zero, t0, t2 csrwi vxrm, 3 /* Rounding mode: round-to-odd */ csrwi vxsat, 1 /* Saturation: encountered */ @@ -120,7 +120,7 @@ func checkasm_get_wrapper, v /* Clobber the saved and temporary registers */ .irp n, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 - .if (\n > 0 && \n < 7) + .if (\n > 1 && \n < 7) mv t\n, t0 .endif fmv.d.x ft\n, t0 @@ -131,9 +131,9 @@ func checkasm_get_wrapper, v /* Call the tested function */ la.tls.ie t0, checked_func add t0, tp, t0 - ld t1, (t0) + ld t3, (t0) sd zero, (t0) - jalr t1 + jalr t3 /* Check special register values */ la.tls.ie t0, saved_regs