[Qemu-devel] [PATCH 15/35] tcg-s390: Query instruction extensions that are installed.

[Richard Henderson <rth@twiddle.net>]

Verify that we have all the instruction extensions that we generate.
Future patches can tailor code generation to the set of instructions
that are present.

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 tcg/s390/tcg-target.c |  113 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 113 insertions(+), 0 deletions(-)

diff --git a/tcg/s390/tcg-target.c b/tcg/s390/tcg-target.c
index 3944cb1..d99bb5c 100644
--- a/tcg/s390/tcg-target.c
+++ b/tcg/s390/tcg-target.c
@@ -229,6 +229,17 @@ static void *qemu_st_helpers[4] = {
 
 static uint8_t *tb_ret_addr;
 
+/* A list of relevant facilities used by this translator.  Some of these
+   are required for proper operation, and these are checked at startup.  */
+
+#define FACILITY_ZARCH		(1ULL << (63 - 1))
+#define FACILITY_ZARCH_ACTIVE	(1ULL << (63 - 2))
+#define FACILITY_LONG_DISP	(1ULL << (63 - 18))
+#define FACILITY_EXT_IMM	(1ULL << (63 - 21))
+#define FACILITY_GEN_INST_EXT	(1ULL << (63 - 34))
+
+static uint64_t facilities;
+
 static void patch_reloc(uint8_t *code_ptr, int type,
                 tcg_target_long value, tcg_target_long addend)
 {
@@ -1177,6 +1188,106 @@ static const TCGTargetOpDef s390_op_defs[] = {
     { -1 },
 };
 
+/* ??? Linux kernels provide an AUXV entry AT_HWCAP that provides most of
+   this information.  However, getting at that entry is not easy this far
+   away from main.  Our options are: start searching from environ, but
+   that fails as soon as someone does a setenv in between.  Read the data
+   from /proc/self/auxv.  Or do the probing ourselves.  The only thing
+   extra that AT_HWCAP gives us is HWCAP_S390_HIGH_GPRS, which indicates
+   that the kernel saves all 64-bits of the registers around traps while
+   in 31-bit mode.  But this is true of all "recent" kernels (ought to dig
+   back and see from when this might not be true).  */
+
+#include <signal.h>
+
+static volatile sig_atomic_t got_sigill;
+
+static void sigill_handler(int sig)
+{
+    got_sigill = 1;
+}
+
+static void query_facilities(void)
+{
+    struct sigaction sa_old, sa_new;
+    register int r0 __asm__("0");
+    register void *r1 __asm__("1");
+    int fail;
+
+    memset(&sa_new, 0, sizeof(sa_new));
+    sa_new.sa_handler = sigill_handler;
+    sigaction(SIGILL, &sa_new, &sa_old);
+
+    /* First, try STORE FACILITY LIST EXTENDED.  If this is present, then
+       we need not do any more probing.  Unfortunately, this itself is an
+       extension and the original STORE FACILITY LIST instruction is
+       kernel-only, storing its results at absolute address 200.  */
+    /* stfle 0(%r1) */
+    r1 = &facilities;
+    asm volatile(".word 0xb2b0,0x1000"
+                 : "=r"(r0) : "0"(0), "r"(r1) : "memory", "cc");
+
+    if (got_sigill) {
+        /* STORE FACILITY EXTENDED is not available.  Probe for one of each
+           kind of instruction that we're interested in.  */
+        /* ??? Possibly some of these are in practice never present unless
+           the store-facility-extended facility is also present.  But since
+           that isn't documented it's just better to probe for each.  */
+
+        /* Test for z/Architecture.  Required even in 31-bit mode.  */
+        got_sigill = 0;
+        /* agr %r0,%r0 */
+        asm volatile(".word 0xb908,0x0000" : "=r"(r0) : : "cc");
+        if (!got_sigill) {
+            facilities |= FACILITY_ZARCH | FACILITY_ZARCH_ACTIVE;
+        }
+
+        /* Test for long displacement.  */
+        got_sigill = 0;
+        /* ly %r0,0(%r1) */
+        r1 = &facilities;
+        asm volatile(".word 0xe300,0x1000,0x0058"
+                     : "=r"(r0) : "r"(r1) : "cc");
+        if (!got_sigill) {
+            facilities |= FACILITY_LONG_DISP;
+        }
+
+        /* Test for extended immediates.  */
+        got_sigill = 0;
+        /* afi %r0,0 */
+        asm volatile(".word 0xc209,0x0000,0x0000" : : : "cc");
+        if (!got_sigill) {
+            facilities |= FACILITY_EXT_IMM;
+        }
+
+        /* Test for general-instructions-extension.  */
+        got_sigill = 0;
+        /* msfi %r0,1 */
+        asm volatile(".word 0xc201,0x0000,0x0001");
+        if (!got_sigill) {
+            facilities |= FACILITY_GEN_INST_EXT;
+        }
+    }
+
+    sigaction(SIGILL, &sa_old, NULL);
+
+    /* The translator currently uses these extensions unconditionally.
+       Pruning this back to the base ESA/390 architecture doesn't seem
+       worthwhile, since even the KVM target requires z/Arch.  */
+    fail = 0;
+    if ((facilities & FACILITY_ZARCH_ACTIVE) == 0) {
+        fprintf(stderr, "TCG: z/Arch facility is required\n");
+        fail = 1;
+    }
+    if ((facilities & FACILITY_LONG_DISP) == 0) {
+        fprintf(stderr, "TCG: long-displacement facility is required\n");
+        fail = 1;
+    }
+    if (fail) {
+        exit(-1);
+    }
+}
+
 void tcg_target_init(TCGContext *s)
 {
 #if !defined(CONFIG_USER_ONLY)
@@ -1186,6 +1297,8 @@ void tcg_target_init(TCGContext *s)
     }
 #endif
 
+    query_facilities();
+
     tcg_regset_set32(tcg_target_available_regs[TCG_TYPE_I32], 0, 0xffff);
     tcg_regset_set32(tcg_target_available_regs[TCG_TYPE_I64], 0, 0xffff);
 
-- 
1.7.0.1