On 04/04/2023 13.36, Nico Boehr wrote:
From: Nina Schoetterl-Glausch <nsg@xxxxxxxxxxxxx>
Test the instruction address used by targets of an execute instruction.
When the target instruction calculates a relative address, the result is
relative to the target instruction, not the execute instruction.
Reviewed-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
Signed-off-by: Nina Schoetterl-Glausch <nsg@xxxxxxxxxxxxx>
Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230317112339.774659-1-nsg@xxxxxxxxxxxxx
Signed-off-by: Nico Boehr <nrb@xxxxxxxxxxxxx>
---
s390x/Makefile | 1 +
s390x/ex.c | 188 ++++++++++++++++++++++++++++++++++++++++++++
s390x/unittests.cfg | 3 +
.gitlab-ci.yml | 1 +
4 files changed, 193 insertions(+)
create mode 100644 s390x/ex.c
diff --git a/s390x/Makefile b/s390x/Makefile
index ab146eb..a80db53 100644
--- a/s390x/Makefile
+++ b/s390x/Makefile
@@ -39,6 +39,7 @@ tests += $(TEST_DIR)/panic-loop-extint.elf
tests += $(TEST_DIR)/panic-loop-pgm.elf
tests += $(TEST_DIR)/migration-sck.elf
tests += $(TEST_DIR)/exittime.elf
+tests += $(TEST_DIR)/ex.elf
pv-tests += $(TEST_DIR)/pv-diags.elf
diff --git a/s390x/ex.c b/s390x/ex.c
new file mode 100644
index 0000000..dbd8030
--- /dev/null
+++ b/s390x/ex.c
@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright IBM Corp. 2023
+ *
+ * Test EXECUTE (RELATIVE LONG).
+ * These instructions execute a target instruction. The target instruction is formed
+ * by reading an instruction from memory and optionally modifying some of its bits.
+ * The execution of the target instruction is the same as if it was executed
+ * normally as part of the instruction sequence, except for the instruction
+ * address and the instruction-length code.
+ */
+
+#include <libcflat.h>
+
+/*
+ * Accesses to the operand of execute-type instructions are instruction fetches.
+ * Minimum alignment is two, since the relative offset is specified by number of halfwords.
+ */
+asm ( ".pushsection .text.exrl_targets,\"x\"\n"
+" .balign 2\n"
+" .popsection\n"
+);
+
+/*
+ * BRANCH AND SAVE, register register variant.
+ * Saves the next instruction address (address from PSW + length of instruction)
+ * to the first register. No branch is taken in this test, because 0 is
+ * specified as target.
+ * BASR does *not* perform a relative address calculation with an intermediate.
+ */
+static void test_basr(void)
+{
+ uint64_t ret_addr, after_ex;
+
+ report_prefix_push("BASR");
+ asm volatile ( ".pushsection .text.exrl_targets\n"
+ "0: basr %[ret_addr],0\n"
+ " .popsection\n"
+
+ " larl %[after_ex],1f\n"
+ " exrl 0,0b\n"
+ "1:\n"
+ : [ret_addr] "=d" (ret_addr),
+ [after_ex] "=d" (after_ex)
+ );
+
+ report(ret_addr == after_ex, "return address after EX");
+ report_prefix_pop();
+}
+
+/*
+ * BRANCH RELATIVE AND SAVE.
+ * According to PoP (Branch-Address Generation), the address calculated relative
+ * to the instruction address is relative to BRAS when it is the target of an
+ * execute-type instruction, not relative to the execute-type instruction.
+ */
+static void test_bras(void)
+{
+ uint64_t after_target, ret_addr, after_ex, branch_addr;
+
+ report_prefix_push("BRAS");
+ asm volatile ( ".pushsection .text.exrl_targets\n"
+ "0: bras %[ret_addr],1f\n"
+ " nopr %%r7\n"
+ "1: larl %[branch_addr],0\n"
+ " j 4f\n"
+ " .popsection\n"
+
+ " larl %[after_target],1b\n"
+ " larl %[after_ex],3f\n"
+ "2: exrl 0,0b\n"
+/*
+ * In case the address calculation is correct, we jump by the relative offset 1b-0b from 0b to 1b.
+ * In case the address calculation is relative to the exrl (i.e. a test failure),
+ * put a valid instruction at the same relative offset from the exrl, so the test continues in a
+ * controlled manner.
+ */
+ "3: larl %[branch_addr],0\n"
+ "4:\n"
+
+ " .if (1b - 0b) != (3b - 2b)\n"
+ " .error \"right and wrong target must have same offset\"\n"
+ " .endif\n"
FWIW, this is failing with Clang 15 for me:
s390x/ex.c:81:4: error: expected absolute expression
" .if (1b - 0b) != (3b - 2b)\n"
^
<inline asm>:12:6: note: instantiated into assembly here
.if (1b - 0b) != (3b - 2b)
^
s390x/ex.c:82:4: error: right and wrong target must have same offset
" .error \"right and wrong target must have same
offset\"\n"
^
<inline asm>:13:2: note: instantiated into assembly here
.error "right and wrong target must have same offset"
^
2 errors generated.
Any easy ways to fix this?
Thomas
