[PATCH 4/4] gdb: Clear tilecfg.start_row for any PC modification.

[Felix Willgerodt via Gdb-patches <gdb-patches@sourceware.org>]

AMX tile instructions are restartable, e.g. on faults.  Tilecfg.start_row
is used to restart the interrupted instructions at the right row.
On inferior calls, jumps or any other PC modification, start_row needs
to be reset.  It binds to the current instruction and not to the one we
would start executing next in these cases.
---
 gdb/amd64-linux-tdep.c                        |  24 ++++
 gdb/testsuite/gdb.arch/amd64-amx-startrow.c   | 122 ++++++++++++++++++
 gdb/testsuite/gdb.arch/amd64-amx-startrow.exp |  91 +++++++++++++
 3 files changed, 237 insertions(+)
 create mode 100644 gdb/testsuite/gdb.arch/amd64-amx-startrow.c
 create mode 100755 gdb/testsuite/gdb.arch/amd64-amx-startrow.exp

diff --git a/gdb/amd64-linux-tdep.c b/gdb/amd64-linux-tdep.c
index cda90de54c6..65cce7f36ed 100644
--- a/gdb/amd64-linux-tdep.c
+++ b/gdb/amd64-linux-tdep.c
@@ -314,6 +314,30 @@ amd64_linux_write_pc (struct regcache *regcache, CORE_ADDR pc)
      within GDB.  In all other cases the system call will not be
      restarted.  */
   regcache_cooked_write_unsigned (regcache, AMD64_LINUX_ORIG_RAX_REGNUM, -1);
+
+  /* If we have interrupted a restart-able AMX instruction we should clear
+     start_row.  Any instructions we will now run should start at row 0.  */
+  i386_gdbarch_tdep *tdep
+      = (i386_gdbarch_tdep *) gdbarch_tdep (regcache->arch ());
+  if (tdep != nullptr && tdep->tilecfg_raw_regnum != -1)
+    {
+      gdb_byte tilecfg_buf[register_size (regcache->arch (),
+					  tdep->tilecfg_raw_regnum)];
+
+      if (regcache->raw_read (tdep->tilecfg_raw_regnum, tilecfg_buf)
+	  != REG_VALID)
+	{
+	  warning (_ ("Could not reset $tilecfg.start_row."));
+	  return;
+	}
+
+      /* start_row is the second byte.  */
+      if (tilecfg_buf[1] != 0)
+	{
+	  tilecfg_buf[1] = 0;
+	  regcache->raw_write (AMD64_AMX_TILECFG_RAW_REGNUM, tilecfg_buf);
+	}
+    }
 }
 
 /* Record all registers but IP register for process-record.  */
diff --git a/gdb/testsuite/gdb.arch/amd64-amx-startrow.c b/gdb/testsuite/gdb.arch/amd64-amx-startrow.c
new file mode 100644
index 00000000000..00650ac5683
--- /dev/null
+++ b/gdb/testsuite/gdb.arch/amd64-amx-startrow.c
@@ -0,0 +1,122 @@
+/* Test program for AMX startrow.
+
+   Copyright 2022 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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 3 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/>.  */
+
+#include <errno.h>
+#include <immintrin.h>
+#include <malloc.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <asm/prctl.h>
+#include <sys/mman.h>
+#include <sys/syscall.h>
+
+#define XFEATURE_XTILEDATA 18
+#define ARCH_REQ_XCOMP_PERM 0x1023
+
+/* To test infcalls.  */
+int
+square (int a, int b)
+{
+  int tmp;
+  tmp = a * b; /* BP2.  */
+  return tmp;
+}
+
+int
+main (int argc, char **argv)
+{
+  /* Ask the OS to configure AMX in xsave.  */
+  if (syscall (SYS_arch_prctl, ARCH_REQ_XCOMP_PERM, XFEATURE_XTILEDATA) != 0)
+    return -1;
+
+  /* Configure tiles.  */
+  struct tileconfig_t
+  {
+    uint8_t palette_id;
+    uint8_t startRow;
+    uint8_t reserved[14];
+    uint16_t cols[16];
+    uint8_t rows[16];
+  };
+
+  const int tmm0 = 0;
+
+  struct tileconfig_t tc = { 1 };
+
+  tc.rows[tmm0] = 16;
+  tc.cols[tmm0] = 64;
+
+  _tile_loadconfig (&tc);
+
+  const uint32_t memA1[16][16]
+    = { { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 },
+	{ 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31 },
+	{ 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47 },
+	{ 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63 },
+	{ 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79 },
+	{ 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95 },
+	{ 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109,
+	  110, 111 },
+	{ 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124,
+	  125, 126, 127 },
+	{ 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140,
+	  141, 142, 143 },
+	{ 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156,
+	  157, 158, 159 },
+	{ 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172,
+	  173, 174, 175 },
+	{ 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188,
+	  189, 190, 191 },
+	{ 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204,
+	  205, 206, 207 },
+	{ 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220,
+	  221, 222, 223 },
+	{ 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236,
+	  237, 238, 239 },
+	{ 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252,
+	  253, 254, 255 } };
+
+  /* Load tile that is stored over a page boundary.  */
+  const long page_size = sysconf (_SC_PAGESIZE);
+  if (page_size == -1)
+    return -1;
+
+  void *p;
+  int ret = posix_memalign (&p, page_size, 2 * page_size);
+  if (ret != 0)
+    return -1;
+
+  void *p2 = p + page_size;
+
+  memmove (p2 - 512, memA1, sizeof (memA1));
+
+  /* Protect the second page to produce a fault.  */
+  if (mprotect (p2, page_size, PROT_NONE) == -1)
+    return -1;
+
+  _tile_loadd (tmm0, p2 - 512, 64); /* BP1.  */
+
+  square (2, 2); /* Jump.  */
+  free (p);
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.arch/amd64-amx-startrow.exp b/gdb/testsuite/gdb.arch/amd64-amx-startrow.exp
new file mode 100755
index 00000000000..201d4aaf767
--- /dev/null
+++ b/gdb/testsuite/gdb.arch/amd64-amx-startrow.exp
@@ -0,0 +1,91 @@
+# Copyright 2022 Free Software Foundation, Inc.
+
+# 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 3 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/>.
+
+# This file tests clearing of tilecfg.startrow in case it isn't empty.
+# If there is a fault, tileload and store instructions can be interrupted.
+# In that case startrow will point to the row on which they should be
+# continued.  In that case, inferior calls and jump commands should clear it.
+# This is tested by placing a tile over two memory pages, creating a page
+# fault.  Watchpoints that have hit will be delivered before the page fault.
+
+if { [skip_amx_tests] } {
+    unsupported "Target does not support AMX."
+    return -1
+}
+
+standard_testfile
+
+if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile} debug] } {
+    return -1
+}
+
+proc test_startrow {test} {
+    global gdb_prompt hex decimal srcfile
+
+    if { ![runto_main] } {
+	untested "could not run to main"
+	return -1
+    }
+
+    set line1 [gdb_get_line_number "BP1"]
+    set line2 [gdb_get_line_number "BP2"]
+    set line_jump [gdb_get_line_number "Jump"]
+    gdb_breakpoint $line1
+    gdb_breakpoint $line2
+
+    gdb_continue_to_breakpoint "line1" ".*$srcfile:$line1.*"
+
+    # Set a watchpoint on the first page, which is un-protected.
+    set watch_addr 0
+    gdb_test_multiple "p/x p2 - 8" "get watch_addr" {
+	-re -wrap "= ($hex)" {
+	    set watch_addr $expect_out(1,string)
+	    pass $gdb_test_name
+	}
+    }
+
+    # If we didn't get a watch_addr, it makes no sense to continue.
+    if { $watch_addr == 0 } {
+	return -1
+    }
+
+    gdb_test "rwatch *(int*) $watch_addr" \
+	"atchpoint $decimal: \\*\\(int\\*\\) $watch_addr"
+
+    gdb_test "continue" \
+	"Continuing.*atchpoint $decimal: \\*\\(int\\*\\) $watch_addr.*"
+
+    gdb_test "p \$tilecfg.start_row" "= \[1-9\]+" "print non-zero start_row"
+
+    if { $test == "jump" } {
+	# Test jump.
+	gdb_test "jump $line_jump" "Breakpoint $decimal, .*$srcfile:$line2.*"
+	gdb_test "p \$tilecfg.start_row" "= 0"
+    } else {
+	# Test infcall.
+	gdb_test "p square (2, 2)" "Breakpoint $decimal, .*$srcfile:$line2.*"
+	gdb_test "p \$tilecfg.start_row" "= 0"
+    }
+}
+
+with_test_prefix "infcall" {
+    test_startrow ""
+}
+
+clean_restart $binfile
+
+with_test_prefix "jump" {
+    test_startrow "jump"
+}
-- 
2.34.1

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