Hexagon (target/hexagon) probe the stores in a packet at start of commit

When a packet has 2 stores, either both commit or neither commit.
At the beginning of gen_commit_packet, we check for multiple stores.
If there are multiple stores, call a helper that will probe each of
them before proceeding with the commit.

Note that we don't call the probe helper for packets with only one
store.  Therefore, we call process_store_log before anything else
involved in committing the packet.

We also fix a typo in the comment in process_store_log.

Test case added in tests/tcg/hexagon/hex_sigsegv.c

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Message-Id: <1633036599-7637-1-git-send-email-tsimpson@quicinc.com>

target/hexagon/helper.h

@@ -89,3 +89,5 @@ DEF_HELPER_4(sffms_lib, f32, env, f32, f32, f32)
 
 DEF_HELPER_3(dfmpyfix, f64, env, f64, f64)
 DEF_HELPER_4(dfmpyhh, f64, env, f64, f64, f64)
+
+DEF_HELPER_2(probe_pkt_scalar_store_s0, void, env, int)

target/hexagon/op_helper.c

@@ -377,6 +377,22 @@ int32_t HELPER(vacsh_pred)(CPUHexagonState *env,
     return PeV;
 }
 
+static void probe_store(CPUHexagonState *env, int slot, int mmu_idx)
+{
+    if (!(env->slot_cancelled & (1 << slot))) {
+        size1u_t width = env->mem_log_stores[slot].width;
+        target_ulong va = env->mem_log_stores[slot].va;
+        uintptr_t ra = GETPC();
+        probe_write(env, va, width, mmu_idx, ra);
+    }
+}
+
+/* Called during packet commit when there are two scalar stores */
+void HELPER(probe_pkt_scalar_store_s0)(CPUHexagonState *env, int mmu_idx)
+{
+    probe_store(env, 0, mmu_idx);
+}
+
 /*
  * mem_noshuf
  * Section 5.5 of the Hexagon V67 Programmer's Reference Manual

target/hexagon/translate.c

@@ -419,7 +419,7 @@ static void process_store_log(DisasContext *ctx, Packet *pkt)
 {
     /*
      *  When a packet has two stores, the hardware processes
-     *  slot 1 and then slot 2.  This will be important when
+     *  slot 1 and then slot 0.  This will be important when
      *  the memory accesses overlap.
      */
     if (pkt->pkt_has_store_s1 && !pkt->pkt_has_dczeroa) {
@@ -471,10 +471,42 @@ static void update_exec_counters(DisasContext *ctx, Packet *pkt)
 
 static void gen_commit_packet(DisasContext *ctx, Packet *pkt)
 {
+    /*
+     * If there is more than one store in a packet, make sure they are all OK
+     * before proceeding with the rest of the packet commit.
+     *
+     * dczeroa has to be the only store operation in the packet, so we go
+     * ahead and process that first.
+     *
+     * When there are two scalar stores, we probe the one in slot 0.
+     *
+     * Note that we don't call the probe helper for packets with only one
+     * store.  Therefore, we call process_store_log before anything else
+     * involved in committing the packet.
+     */
+    bool has_store_s0 = pkt->pkt_has_store_s0;
+    bool has_store_s1 = (pkt->pkt_has_store_s1 && !ctx->s1_store_processed);
+    if (pkt->pkt_has_dczeroa) {
+        /*
+         * The dczeroa will be the store in slot 0, check that we don't have
+         * a store in slot 1.
+         */
+        g_assert(has_store_s0 && !has_store_s1);
+        process_dczeroa(ctx, pkt);
+    } else if (has_store_s0 && has_store_s1) {
+        /*
+         * process_store_log will execute the slot 1 store first,
+         * so we only have to probe the store in slot 0
+         */
+        TCGv mem_idx = tcg_const_tl(ctx->mem_idx);
+        gen_helper_probe_pkt_scalar_store_s0(cpu_env, mem_idx);
+        tcg_temp_free(mem_idx);
+    }
+
+    process_store_log(ctx, pkt);
+
     gen_reg_writes(ctx);
     gen_pred_writes(ctx, pkt);
-    process_store_log(ctx, pkt);
-    process_dczeroa(ctx, pkt);
     update_exec_counters(ctx, pkt);
     if (HEX_DEBUG) {
         TCGv has_st0 =

tests/tcg/hexagon/Makefile.target

@@ -28,6 +28,7 @@ first: $(HEX_SRC)/first.S
 	$(CC) -static -mv67 -nostdlib $^ -o $@
 
 HEX_TESTS = first
+HEX_TESTS += hex_sigsegv
 HEX_TESTS += misc
 HEX_TESTS += preg_alias
 HEX_TESTS += dual_stores

tests/tcg/hexagon/hex_sigsegv.c

@@ -0,0 +1,106 @@
+/*
+ *  Copyright(c) 2021 Qualcomm Innovation Center, Inc. All Rights Reserved.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * Test the VLIW semantics of two stores in a packet
+ *
+ * When a packet has 2 stores, either both commit or neither commit.
+ * We test this with a packet that does stores to both NULL and a global
+ * variable, "should_not_change".  After the SIGSEGV is caught, we check
+ * that the "should_not_change" value is the same.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <fcntl.h>
+#include <setjmp.h>
+#include <signal.h>
+
+typedef unsigned char uint8_t;
+
+int err;
+int segv_caught;
+
+#define SHOULD_NOT_CHANGE_VAL        5
+int should_not_change = SHOULD_NOT_CHANGE_VAL;
+
+#define BUF_SIZE        300
+unsigned char buf[BUF_SIZE];
+
+
+static void __check(const char *filename, int line, int x, int expect)
+{
+    if (x != expect) {
+        printf("ERROR %s:%d - %d != %d\n",
+               filename, line, x, expect);
+        err++;
+    }
+}
+
+#define check(x, expect) __check(__FILE__, __LINE__, (x), (expect))
+
+static void __chk_error(const char *filename, int line, int ret)
+{
+    if (ret < 0) {
+        printf("ERROR %s:%d - %d\n", filename, line, ret);
+        err++;
+    }
+}
+
+#define chk_error(ret) __chk_error(__FILE__, __LINE__, (ret))
+
+jmp_buf jmp_env;
+
+static void sig_segv(int sig, siginfo_t *info, void *puc)
+{
+    check(sig, SIGSEGV);
+    segv_caught = 1;
+    longjmp(jmp_env, 1);
+}
+
+int main()
+{
+    struct sigaction act;
+
+    /* SIGSEGV test */
+    act.sa_sigaction = sig_segv;
+    sigemptyset(&act.sa_mask);
+    act.sa_flags = SA_SIGINFO;
+    chk_error(sigaction(SIGSEGV, &act, NULL));
+    if (setjmp(jmp_env) == 0) {
+        asm volatile("r18 = ##should_not_change\n\t"
+                     "r19 = #0\n\t"
+                     "{\n\t"
+                     "    memw(r18) = #7\n\t"
+                     "    memw(r19) = #0\n\t"
+                     "}\n\t"
+                      : : : "r18", "r19", "memory");
+    }
+
+    act.sa_handler = SIG_DFL;
+    sigemptyset(&act.sa_mask);
+    act.sa_flags = 0;
+    chk_error(sigaction(SIGSEGV, &act, NULL));
+
+    check(segv_caught, 1);
+    check(should_not_change, SHOULD_NOT_CHANGE_VAL);
+
+    puts(err ? "FAIL" : "PASS");
+    return err ? EXIT_FAILURE : EXIT_SUCCESS;
+}