target/s390x: Make translator stop before the end of a page

Right now translator stops right *after* the end of a page, which
breaks reporting of fault locations when the last instruction of a
multi-insn translation block crosses a page boundary.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220817150506.592862-3-iii@linux.ibm.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

target/s390x/tcg/translate.c

@@ -6609,6 +6609,14 @@ static void s390x_tr_insn_start(DisasContextBase *dcbase, CPUState *cs)
     dc->insn_start = tcg_last_op();
 }
 
+static target_ulong get_next_pc(CPUS390XState *env, DisasContext *s,
+                                uint64_t pc)
+{
+    uint64_t insn = ld_code2(env, s, pc);
+
+    return pc + get_ilen((insn >> 8) & 0xff);
+}
+
 static void s390x_tr_translate_insn(DisasContextBase *dcbase, CPUState *cs)
 {
     CPUS390XState *env = cs->env_ptr;
@@ -6616,10 +6624,9 @@ static void s390x_tr_translate_insn(DisasContextBase *dcbase, CPUState *cs)
 
     dc->base.is_jmp = translate_one(env, dc);
     if (dc->base.is_jmp == DISAS_NEXT) {
-        uint64_t page_start;
-
-        page_start = dc->base.pc_first & TARGET_PAGE_MASK;
-        if (dc->base.pc_next - page_start >= TARGET_PAGE_SIZE || dc->ex_value) {
+        if (!is_same_page(dcbase, dc->base.pc_next) ||
+            !is_same_page(dcbase, get_next_pc(env, dc, dc->base.pc_next)) ||
+            dc->ex_value) {
             dc->base.is_jmp = DISAS_TOO_MANY;
         }
     }

tests/tcg/multiarch/noexec.c.inc

@@ -0,0 +1,139 @@
+/*
+ * Common code for arch-specific MMU_INST_FETCH fault testing.
+ */
+
+#define _GNU_SOURCE
+
+#include <assert.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <sys/ucontext.h>
+
+/* Forward declarations. */
+
+static void *arch_mcontext_pc(const mcontext_t *ctx);
+static int arch_mcontext_arg(const mcontext_t *ctx);
+static void arch_flush(void *p, int len);
+
+/* Testing infrastructure. */
+
+struct noexec_test {
+    const char *name;
+    const char *test_code;
+    int test_len;
+    int page_ofs;
+    int entry_ofs;
+    int expected_si_ofs;
+    int expected_pc_ofs;
+    int expected_arg;
+};
+
+static void *page_base;
+static int page_size;
+static const struct noexec_test *current_noexec_test;
+
+static void handle_err(const char *syscall)
+{
+    printf("[  FAILED  ] %s: %s\n", syscall, strerror(errno));
+    exit(EXIT_FAILURE);
+}
+
+static void handle_segv(int sig, siginfo_t *info, void *ucontext)
+{
+    const struct noexec_test *test = current_noexec_test;
+    const mcontext_t *mc = &((ucontext_t *)ucontext)->uc_mcontext;
+    void *expected_si;
+    void *expected_pc;
+    void *pc;
+    int arg;
+
+    if (test == NULL) {
+        printf("[  FAILED  ] unexpected SEGV\n");
+        exit(EXIT_FAILURE);
+    }
+    current_noexec_test = NULL;
+
+    expected_si = page_base + test->expected_si_ofs;
+    if (info->si_addr != expected_si) {
+        printf("[  FAILED  ] wrong si_addr (%p != %p)\n",
+               info->si_addr, expected_si);
+        exit(EXIT_FAILURE);
+    }
+
+    pc = arch_mcontext_pc(mc);
+    expected_pc = page_base + test->expected_pc_ofs;
+    if (pc != expected_pc) {
+        printf("[  FAILED  ] wrong pc (%p != %p)\n", pc, expected_pc);
+        exit(EXIT_FAILURE);
+    }
+
+    arg = arch_mcontext_arg(mc);
+    if (arg != test->expected_arg) {
+        printf("[  FAILED  ] wrong arg (%d != %d)\n", arg, test->expected_arg);
+        exit(EXIT_FAILURE);
+    }
+
+    if (mprotect(page_base, page_size,
+                 PROT_READ | PROT_WRITE | PROT_EXEC) < 0) {
+        handle_err("mprotect");
+    }
+}
+
+static void test_noexec_1(const struct noexec_test *test)
+{
+    void *start = page_base + test->page_ofs;
+    void (*fn)(int arg) = page_base + test->entry_ofs;
+
+    memcpy(start, test->test_code, test->test_len);
+    arch_flush(start, test->test_len);
+
+    /* Trigger TB creation in order to test invalidation. */
+    fn(0);
+
+    if (mprotect(page_base, page_size, PROT_NONE) < 0) {
+        handle_err("mprotect");
+    }
+
+    /* Trigger SEGV and check that handle_segv() ran. */
+    current_noexec_test = test;
+    fn(0);
+    assert(current_noexec_test == NULL);
+}
+
+static int test_noexec(struct noexec_test *tests, size_t n_tests)
+{
+    struct sigaction act;
+    size_t i;
+
+    memset(&act, 0, sizeof(act));
+    act.sa_sigaction = handle_segv;
+    act.sa_flags = SA_SIGINFO;
+    if (sigaction(SIGSEGV, &act, NULL) < 0) {
+        handle_err("sigaction");
+    }
+
+    page_size = getpagesize();
+    page_base = mmap(NULL, 2 * page_size,
+                     PROT_READ | PROT_WRITE | PROT_EXEC,
+                     MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+    if (page_base == MAP_FAILED) {
+        handle_err("mmap");
+    }
+    page_base += page_size;
+
+    for (i = 0; i < n_tests; i++) {
+        struct noexec_test *test = &tests[i];
+
+        printf("[ RUN      ] %s\n", test->name);
+        test_noexec_1(test);
+        printf("[       OK ]\n");
+    }
+
+    printf("[  PASSED  ]\n");
+    return EXIT_SUCCESS;
+}

tests/tcg/s390x/Makefile.target

@@ -16,6 +16,7 @@ TESTS+=shift
 TESTS+=trap
 TESTS+=signals-s390x
 TESTS+=branch-relative-long
+TESTS+=noexec
 
 Z14_TESTS=vfminmax
 vfminmax: LDFLAGS+=-lm

tests/tcg/s390x/noexec.c

@@ -0,0 +1,106 @@
+#include "../multiarch/noexec.c.inc"
+
+static void *arch_mcontext_pc(const mcontext_t *ctx)
+{
+    return (void *)ctx->psw.addr;
+}
+
+static int arch_mcontext_arg(const mcontext_t *ctx)
+{
+    return ctx->gregs[2];
+}
+
+static void arch_flush(void *p, int len)
+{
+}
+
+extern char noexec_1[];
+extern char noexec_2[];
+extern char noexec_end[];
+
+asm("noexec_1:\n"
+    "   lgfi %r2,1\n"       /* %r2 is 0 on entry, set 1. */
+    "noexec_2:\n"
+    "   lgfi %r2,2\n"       /* %r2 is 0/1; set 2. */
+    "   br %r14\n"          /* return */
+    "noexec_end:");
+
+extern char exrl_1[];
+extern char exrl_2[];
+extern char exrl_end[];
+
+asm("exrl_1:\n"
+    "   exrl %r0, exrl_2\n"
+    "   br %r14\n"
+    "exrl_2:\n"
+    "   lgfi %r2,2\n"
+    "exrl_end:");
+
+int main(void)
+{
+    struct noexec_test noexec_tests[] = {
+        {
+            .name = "fallthrough",
+            .test_code = noexec_1,
+            .test_len = noexec_end - noexec_1,
+            .page_ofs = noexec_1 - noexec_2,
+            .entry_ofs = noexec_1 - noexec_2,
+            .expected_si_ofs = 0,
+            .expected_pc_ofs = 0,
+            .expected_arg = 1,
+        },
+        {
+            .name = "jump",
+            .test_code = noexec_1,
+            .test_len = noexec_end - noexec_1,
+            .page_ofs = noexec_1 - noexec_2,
+            .entry_ofs = 0,
+            .expected_si_ofs = 0,
+            .expected_pc_ofs = 0,
+            .expected_arg = 0,
+        },
+        {
+            .name = "exrl",
+            .test_code = exrl_1,
+            .test_len = exrl_end - exrl_1,
+            .page_ofs = exrl_1 - exrl_2,
+            .entry_ofs = exrl_1 - exrl_2,
+            .expected_si_ofs = 0,
+            .expected_pc_ofs = exrl_1 - exrl_2,
+            .expected_arg = 0,
+        },
+        {
+            .name = "fallthrough [cross]",
+            .test_code = noexec_1,
+            .test_len = noexec_end - noexec_1,
+            .page_ofs = noexec_1 - noexec_2 - 2,
+            .entry_ofs = noexec_1 - noexec_2 - 2,
+            .expected_si_ofs = 0,
+            .expected_pc_ofs = -2,
+            .expected_arg = 1,
+        },
+        {
+            .name = "jump [cross]",
+            .test_code = noexec_1,
+            .test_len = noexec_end - noexec_1,
+            .page_ofs = noexec_1 - noexec_2 - 2,
+            .entry_ofs = -2,
+            .expected_si_ofs = 0,
+            .expected_pc_ofs = -2,
+            .expected_arg = 0,
+        },
+        {
+            .name = "exrl [cross]",
+            .test_code = exrl_1,
+            .test_len = exrl_end - exrl_1,
+            .page_ofs = exrl_1 - exrl_2 - 2,
+            .entry_ofs = exrl_1 - exrl_2 - 2,
+            .expected_si_ofs = 0,
+            .expected_pc_ofs = exrl_1 - exrl_2 - 2,
+            .expected_arg = 0,
+        },
+    };
+
+    return test_noexec(noexec_tests,
+                       sizeof(noexec_tests) / sizeof(noexec_tests[0]));
+}