[PATCH v4 0/3] linux-user: Allow gdbstub to ignore page protection

[PATCH v4 0/3] linux-user: Allow gdbstub to ignore page protection

[Ilya Leoshkevich]

v3: https://lists.gnu.org/archive/html/qemu-devel/2024-01/msg02907.html
v3 -> v4: Hide InteractiveConsole behind QEMU_TEST_INTERACTIVE (Alex).
          Probe /proc/self/mem in the PROT_NONE test.

v2: https://lists.gnu.org/archive/html/qemu-devel/2024-01/msg01592.html
v2 -> v3: Add Richard's R-b on [1/3].
          Fix printing the architecture name and the number of failures
          in test_gdbstub.py.
          Patches that need review: [2/3] and [3/3].

v1: https://lists.gnu.org/archive/html/qemu-devel/2024-01/msg01314.html
v1 -> v2: Use /proc/self/mem as a fallback. Handle TB invalidation
          (Richard).
          Test cross-page accesses.

RFC: https://lists.gnu.org/archive/html/qemu-devel/2023-12/msg02044.html
RFC -> v1: Use /proc/self/mem and accept that this will not work
           without /proc.
           Factor out a couple functions for gdbstub testing.
           Add a test.

Hi,

I've noticed that gdbstub behaves differently from gdbserver in that it
doesn't allow reading non-readable pages. This series improves the
situation by using the same mechanism as gdbserver: /proc/self/mem.

Best regards,
Ilya

Ilya Leoshkevich (3):
  linux-user: Allow gdbstub to ignore page protection
  tests/tcg: Factor out gdbstub test functions
  tests/tcg: Add the PROT_NONE gdbstub test

 cpu-target.c                                  | 78 +++++++++++++++----
 tests/guest-debug/run-test.py                 |  7 +-
 tests/guest-debug/test_gdbstub.py             | 60 ++++++++++++++
 tests/tcg/aarch64/gdbstub/test-sve-ioctl.py   | 34 +-------
 tests/tcg/aarch64/gdbstub/test-sve.py         | 33 +-------
 tests/tcg/multiarch/Makefile.target           |  9 ++-
 tests/tcg/multiarch/gdbstub/interrupt.py      | 47 ++---------
 tests/tcg/multiarch/gdbstub/memory.py         | 41 +---------
 tests/tcg/multiarch/gdbstub/prot-none.py      | 36 +++++++++
 tests/tcg/multiarch/gdbstub/registers.py      | 41 ++--------
 tests/tcg/multiarch/gdbstub/sha1.py           | 40 ++--------
 .../multiarch/gdbstub/test-proc-mappings.py   | 39 +---------
 .../multiarch/gdbstub/test-qxfer-auxv-read.py | 37 +--------
 .../gdbstub/test-thread-breakpoint.py         | 37 +--------
 tests/tcg/multiarch/prot-none.c               | 40 ++++++++++
 tests/tcg/s390x/gdbstub/test-signals-s390x.py | 42 +---------
 tests/tcg/s390x/gdbstub/test-svc.py           | 39 +---------
 17 files changed, 247 insertions(+), 413 deletions(-)
 create mode 100644 tests/guest-debug/test_gdbstub.py
 create mode 100644 tests/tcg/multiarch/gdbstub/prot-none.py
 create mode 100644 tests/tcg/multiarch/prot-none.c

-- 
2.43.0

[PATCH v4 1/3] linux-user: Allow gdbstub to ignore page protection

[Ilya Leoshkevich]

gdbserver ignores page protection by virtue of using /proc/$pid/mem.
Teach qemu gdbstub to do this too. This will not work if /proc is not
mounted; accept this limitation.

One alternative is to temporarily grant the missing PROT_* bit, but
this is inherently racy. Another alternative is self-debugging with
ptrace(POKE), which will break if QEMU itself is being debugged - a
much more severe limitation.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 cpu-target.c | 78 ++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 63 insertions(+), 15 deletions(-)

diff --git a/cpu-target.c b/cpu-target.c
index f6e07c3deb1..958d63e8823 100644
--- a/cpu-target.c
+++ b/cpu-target.c
@@ -382,6 +382,9 @@ int cpu_memory_rw_debug(CPUState *cpu, vaddr addr,
     vaddr l, page;
     void * p;
     uint8_t *buf = ptr;
+    ssize_t written;
+    int ret = -1;
+    int fd = -1;
 
     while (len > 0) {
         page = addr & TARGET_PAGE_MASK;
@@ -389,30 +392,75 @@ int cpu_memory_rw_debug(CPUState *cpu, vaddr addr,
         if (l > len)
             l = len;
         flags = page_get_flags(page);
-        if (!(flags & PAGE_VALID))
-            return -1;
+        if (!(flags & PAGE_VALID)) {
+            goto out_close;
+        }
         if (is_write) {
-            if (!(flags & PAGE_WRITE))
-                return -1;
-            /* XXX: this code should not depend on lock_user */
-            if (!(p = lock_user(VERIFY_WRITE, addr, l, 0)))
-                return -1;
-            memcpy(p, buf, l);
-            unlock_user(p, addr, l);
-        } else {
-            if (!(flags & PAGE_READ))
-                return -1;
+            if (flags & PAGE_WRITE) {
+                /* XXX: this code should not depend on lock_user */
+                p = lock_user(VERIFY_WRITE, addr, l, 0);
+                if (!p) {
+                    goto out_close;
+                }
+                memcpy(p, buf, l);
+                unlock_user(p, addr, l);
+            } else {
+                /* Bypass the host page protection using ptrace. */
+                if (fd == -1) {
+                    fd = open("/proc/self/mem", O_WRONLY);
+                    if (fd == -1) {
+                        goto out;
+                    }
+                }
+                /*
+                 * If there is a TranslationBlock and we weren't bypassing the
+                 * host page protection, the memcpy() above would SEGV,
+                 * ultimately leading to page_unprotect(). So invalidate the
+                 * translations manually. Both invalidation and pwrite() must
+                 * be under mmap_lock() in order to prevent the creation of
+                 * another TranslationBlock in between.
+                 */
+                mmap_lock();
+                tb_invalidate_phys_range(addr, addr + l - 1);
+                written = pwrite(fd, buf, l,
+                                 (off_t)(uintptr_t)g2h_untagged(addr));
+                mmap_unlock();
+                if (written != l) {
+                    goto out_close;
+                }
+            }
+        } else if (flags & PAGE_READ) {
             /* XXX: this code should not depend on lock_user */
-            if (!(p = lock_user(VERIFY_READ, addr, l, 1)))
-                return -1;
+            p = lock_user(VERIFY_READ, addr, l, 1);
+            if (!p) {
+                goto out_close;
+            }
             memcpy(buf, p, l);
             unlock_user(p, addr, 0);
+        } else {
+            /* Bypass the host page protection using ptrace. */
+            if (fd == -1) {
+                fd = open("/proc/self/mem", O_RDONLY);
+                if (fd == -1) {
+                    goto out;
+                }
+            }
+            if (pread(fd, buf, l,
+                      (off_t)(uintptr_t)g2h_untagged(addr)) != l) {
+                goto out_close;
+            }
         }
         len -= l;
         buf += l;
         addr += l;
     }
-    return 0;
+    ret = 0;
+out_close:
+    if (fd != -1) {
+        close(fd);
+    }
+out:
+    return ret;
 }
 #endif
 
-- 
2.43.0

[PATCH v4 2/3] tests/tcg: Factor out gdbstub test functions

[Ilya Leoshkevich]

Both the report() function as well as the initial gdbstub test sequence
are copy-pasted into ~10 files with slight modifications. This
indicates that they are indeed generic, so factor them out. While
at it, add a few newlines to make the formatting closer to PEP-8.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 tests/guest-debug/run-test.py                 |  7 ++-
 tests/guest-debug/test_gdbstub.py             | 60 +++++++++++++++++++
 tests/tcg/aarch64/gdbstub/test-sve-ioctl.py   | 34 +----------
 tests/tcg/aarch64/gdbstub/test-sve.py         | 33 +---------
 tests/tcg/multiarch/gdbstub/interrupt.py      | 47 ++-------------
 tests/tcg/multiarch/gdbstub/memory.py         | 41 +------------
 tests/tcg/multiarch/gdbstub/registers.py      | 41 ++-----------
 tests/tcg/multiarch/gdbstub/sha1.py           | 40 ++-----------
 .../multiarch/gdbstub/test-proc-mappings.py   | 39 +-----------
 .../multiarch/gdbstub/test-qxfer-auxv-read.py | 37 +-----------
 .../gdbstub/test-thread-breakpoint.py         | 37 +-----------
 tests/tcg/s390x/gdbstub/test-signals-s390x.py | 42 +------------
 tests/tcg/s390x/gdbstub/test-svc.py           | 39 +-----------
 13 files changed, 100 insertions(+), 397 deletions(-)
 create mode 100644 tests/guest-debug/test_gdbstub.py

diff --git a/tests/guest-debug/run-test.py b/tests/guest-debug/run-test.py
index b13b27d4b19..368ff8a8903 100755
--- a/tests/guest-debug/run-test.py
+++ b/tests/guest-debug/run-test.py
@@ -97,7 +97,12 @@ def log(output, msg):
     sleep(1)
     log(output, "GDB CMD: %s" % (gdb_cmd))
 
-    result = subprocess.call(gdb_cmd, shell=True, stdout=output, stderr=stderr)
+    gdb_env = dict(os.environ)
+    gdb_pythonpath = gdb_env.get("PYTHONPATH", "").split(os.pathsep)
+    gdb_pythonpath.append(os.path.dirname(os.path.realpath(__file__)))
+    gdb_env["PYTHONPATH"] = os.pathsep.join(gdb_pythonpath)
+    result = subprocess.call(gdb_cmd, shell=True, stdout=output, stderr=stderr,
+                             env=gdb_env)
 
     # A result of greater than 128 indicates a fatal signal (likely a
     # crash due to gdb internal failure). That's a problem for GDB and
diff --git a/tests/guest-debug/test_gdbstub.py b/tests/guest-debug/test_gdbstub.py
new file mode 100644
index 00000000000..7f71d34da16
--- /dev/null
+++ b/tests/guest-debug/test_gdbstub.py
@@ -0,0 +1,60 @@
+"""Helper functions for gdbstub testing
+
+"""
+from __future__ import print_function
+import gdb
+import os
+import sys
+import traceback
+
+fail_count = 0
+
+
+def report(cond, msg):
+    """Report success/fail of a test"""
+    if cond:
+        print("PASS: {}".format(msg))
+    else:
+        print("FAIL: {}".format(msg))
+        global fail_count
+        fail_count += 1
+
+
+def main(test, expected_arch=None):
+    """Run a test function
+
+    This runs as the script it sourced (via -x, via run-test.py)."""
+    try:
+        inferior = gdb.selected_inferior()
+        arch = inferior.architecture()
+        print("ATTACHED: {}".format(arch.name()))
+        if expected_arch is not None:
+            report(arch.name() == expected_arch,
+                   "connected to {}".format(expected_arch))
+    except (gdb.error, AttributeError):
+        print("SKIP: not connected")
+        exit(0)
+
+    if gdb.parse_and_eval("$pc") == 0:
+        print("SKIP: PC not set")
+        exit(0)
+
+    try:
+        test()
+    except:
+        print("GDB Exception:")
+        traceback.print_exc(file=sys.stdout)
+        global fail_count
+        fail_count += 1
+        if "QEMU_TEST_INTERACTIVE" in os.environ:
+            import code
+            code.InteractiveConsole(locals=globals()).interact()
+        raise
+
+    try:
+        gdb.execute("kill")
+    except gdb.error:
+        pass
+
+    print("All tests complete: {} failures".format(fail_count))
+    exit(fail_count)
diff --git a/tests/tcg/aarch64/gdbstub/test-sve-ioctl.py b/tests/tcg/aarch64/gdbstub/test-sve-ioctl.py
index ee8d467e59d..a78a3a2514d 100644
--- a/tests/tcg/aarch64/gdbstub/test-sve-ioctl.py
+++ b/tests/tcg/aarch64/gdbstub/test-sve-ioctl.py
@@ -8,19 +8,10 @@
 #
 
 import gdb
-import sys
+from test_gdbstub import main, report
 
 initial_vlen = 0
-failcount = 0
 
-def report(cond, msg):
-    "Report success/fail of test"
-    if cond:
-        print ("PASS: %s" % (msg))
-    else:
-        print ("FAIL: %s" % (msg))
-        global failcount
-        failcount += 1
 
 class TestBreakpoint(gdb.Breakpoint):
     def __init__(self, sym_name="__sve_ld_done"):
@@ -64,26 +55,5 @@ def run_test():
 
     gdb.execute("c")
 
-#
-# This runs as the script it sourced (via -x, via run-test.py)
-#
-try:
-    inferior = gdb.selected_inferior()
-    arch = inferior.architecture()
-    report(arch.name() == "aarch64", "connected to aarch64")
-except (gdb.error, AttributeError):
-    print("SKIPPING (not connected)", file=sys.stderr)
-    exit(0)
-
-try:
-    # Run the actual tests
-    run_test()
-except:
-    print ("GDB Exception: %s" % (sys.exc_info()[0]))
-    failcount += 1
-    import code
-    code.InteractiveConsole(locals=globals()).interact()
-    raise
 
-print("All tests complete: %d failures" % failcount)
-exit(failcount)
+main(run_test, expected_arch="aarch64")
diff --git a/tests/tcg/aarch64/gdbstub/test-sve.py b/tests/tcg/aarch64/gdbstub/test-sve.py
index afd8ece98dd..84cdcd4a32e 100644
--- a/tests/tcg/aarch64/gdbstub/test-sve.py
+++ b/tests/tcg/aarch64/gdbstub/test-sve.py
@@ -6,20 +6,10 @@
 #
 
 import gdb
-import sys
+from test_gdbstub import main, report
 
 MAGIC = 0xDEADBEEF
 
-failcount = 0
-
-def report(cond, msg):
-    "Report success/fail of test"
-    if cond:
-        print ("PASS: %s" % (msg))
-    else:
-        print ("FAIL: %s" % (msg))
-        global failcount
-        failcount += 1
 
 def run_test():
     "Run through the tests one by one"
@@ -54,24 +44,5 @@ def run_test():
             report(str(v.type) == "uint64_t", "size of %s" % (reg))
             report(int(v) == MAGIC, "%s is 0x%x" % (reg, MAGIC))
 
-#
-# This runs as the script it sourced (via -x, via run-test.py)
-#
-try:
-    inferior = gdb.selected_inferior()
-    arch = inferior.architecture()
-    report(arch.name() == "aarch64", "connected to aarch64")
-except (gdb.error, AttributeError):
-    print("SKIPPING (not connected)", file=sys.stderr)
-    exit(0)
-
-try:
-    # Run the actual tests
-    run_test()
-except:
-    print ("GDB Exception: %s" % (sys.exc_info()[0]))
-    failcount += 1
-
-print("All tests complete: %d failures" % failcount)
 
-exit(failcount)
+main(run_test, expected_arch="aarch64")
diff --git a/tests/tcg/multiarch/gdbstub/interrupt.py b/tests/tcg/multiarch/gdbstub/interrupt.py
index c016e7afbbf..90a45b5140a 100644
--- a/tests/tcg/multiarch/gdbstub/interrupt.py
+++ b/tests/tcg/multiarch/gdbstub/interrupt.py
@@ -8,19 +8,7 @@
 #
 
 import gdb
-import sys
-
-failcount = 0
-
-
-def report(cond, msg):
-    "Report success/fail of test"
-    if cond:
-        print("PASS: %s" % (msg))
-    else:
-        print("FAIL: %s" % (msg))
-        global failcount
-        failcount += 1
+from test_gdbstub import main, report
 
 
 def check_interrupt(thread):
@@ -59,6 +47,9 @@ def run_test():
     Test if interrupting the code always lands us on the same thread when
     running with scheduler-lock enabled.
     """
+    if len(gdb.selected_inferior().threads()) == 1:
+        print("SKIP: set to run on a single thread")
+        exit(0)
 
     gdb.execute("set scheduler-locking on")
     for thread in gdb.selected_inferior().threads():
@@ -66,32 +57,4 @@ def run_test():
                "thread %d resumes correctly on interrupt" % thread.num)
 
 
-#
-# This runs as the script it sourced (via -x, via run-test.py)
-#
-try:
-    inferior = gdb.selected_inferior()
-    arch = inferior.architecture()
-    print("ATTACHED: %s" % arch.name())
-except (gdb.error, AttributeError):
-    print("SKIPPING (not connected)", file=sys.stderr)
-    exit(0)
-
-if gdb.parse_and_eval('$pc') == 0:
-    print("SKIP: PC not set")
-    exit(0)
-if len(gdb.selected_inferior().threads()) == 1:
-    print("SKIP: set to run on a single thread")
-    exit(0)
-
-try:
-    # Run the actual tests
-    run_test()
-except (gdb.error):
-    print("GDB Exception: %s" % (sys.exc_info()[0]))
-    failcount += 1
-    pass
-
-# Finally kill the inferior and exit gdb with a count of failures
-gdb.execute("kill")
-exit(failcount)
+main(run_test)
diff --git a/tests/tcg/multiarch/gdbstub/memory.py b/tests/tcg/multiarch/gdbstub/memory.py
index fb1d06b7bb7..532b92e7fb3 100644
--- a/tests/tcg/multiarch/gdbstub/memory.py
+++ b/tests/tcg/multiarch/gdbstub/memory.py
@@ -9,18 +9,7 @@
 
 import gdb
 import sys
-
-failcount = 0
-
-
-def report(cond, msg):
-    "Report success/fail of test"
-    if cond:
-        print("PASS: %s" % (msg))
-    else:
-        print("FAIL: %s" % (msg))
-        global failcount
-        failcount += 1
+from test_gdbstub import main, report
 
 
 def check_step():
@@ -99,29 +88,5 @@ def run_test():
 
     report(cbp.hit_count == 0, "didn't reach backstop")
 
-#
-# This runs as the script it sourced (via -x, via run-test.py)
-#
-try:
-    inferior = gdb.selected_inferior()
-    arch = inferior.architecture()
-    print("ATTACHED: %s" % arch.name())
-except (gdb.error, AttributeError):
-    print("SKIPPING (not connected)", file=sys.stderr)
-    exit(0)
-
-if gdb.parse_and_eval('$pc') == 0:
-    print("SKIP: PC not set")
-    exit(0)
-
-try:
-    # Run the actual tests
-    run_test()
-except (gdb.error):
-    print("GDB Exception: %s" % (sys.exc_info()[0]))
-    failcount += 1
-    pass
-
-# Finally kill the inferior and exit gdb with a count of failures
-gdb.execute("kill")
-exit(failcount)
+
+main(run_test)
diff --git a/tests/tcg/multiarch/gdbstub/registers.py b/tests/tcg/multiarch/gdbstub/registers.py
index 688c0611072..b3d13cb077f 100644
--- a/tests/tcg/multiarch/gdbstub/registers.py
+++ b/tests/tcg/multiarch/gdbstub/registers.py
@@ -7,20 +7,11 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
 import gdb
-import sys
 import xml.etree.ElementTree as ET
+from test_gdbstub import main, report
 
-initial_vlen = 0
-failcount = 0
 
-def report(cond, msg):
-    "Report success/fail of test."
-    if cond:
-        print("PASS: %s" % (msg))
-    else:
-        print("FAIL: %s" % (msg))
-        global failcount
-        failcount += 1
+initial_vlen = 0
 
 
 def fetch_xml_regmap():
@@ -75,6 +66,7 @@ def fetch_xml_regmap():
 
     return reg_map
 
+
 def get_register_by_regnum(reg_map, regnum):
     """
     Helper to find a register from the map via its XML regnum
@@ -84,6 +76,7 @@ def get_register_by_regnum(reg_map, regnum):
             return entry
     return None
 
+
 def crosscheck_remote_xml(reg_map):
     """
     Cross-check the list of remote-registers with the XML info.
@@ -144,6 +137,7 @@ def crosscheck_remote_xml(reg_map):
         elif "seen" not in x_reg:
             print(f"{x_reg} wasn't seen in remote-registers")
 
+
 def initial_register_read(reg_map):
     """
     Do an initial read of all registers that we know gdb cares about
@@ -214,27 +208,4 @@ def run_test():
         complete_and_diff(reg_map)
 
 
-#
-# This runs as the script it sourced (via -x, via run-test.py)
-#
-try:
-    inferior = gdb.selected_inferior()
-    arch = inferior.architecture()
-    print("ATTACHED: %s" % arch.name())
-except (gdb.error, AttributeError):
-    print("SKIPPING (not connected)", file=sys.stderr)
-    exit(0)
-
-if gdb.parse_and_eval('$pc') == 0:
-    print("SKIP: PC not set")
-    exit(0)
-
-try:
-    run_test()
-except (gdb.error):
-    print ("GDB Exception: %s" % (sys.exc_info()[0]))
-    failcount += 1
-    pass
-
-print("All tests complete: %d failures" % failcount)
-exit(failcount)
+main(run_test)
diff --git a/tests/tcg/multiarch/gdbstub/sha1.py b/tests/tcg/multiarch/gdbstub/sha1.py
index 416728415f9..1ce711a402c 100644
--- a/tests/tcg/multiarch/gdbstub/sha1.py
+++ b/tests/tcg/multiarch/gdbstub/sha1.py
@@ -7,19 +7,11 @@
 #
 
 import gdb
-import sys
+from test_gdbstub import main, report
+
 
 initial_vlen = 0
-failcount = 0
 
-def report(cond, msg):
-    "Report success/fail of test"
-    if cond:
-        print("PASS: %s" % (msg))
-    else:
-        print("FAIL: %s" % (msg))
-        global failcount
-        failcount += 1
 
 def check_break(sym_name):
     "Setup breakpoint, continue and check we stopped."
@@ -35,6 +27,7 @@ def check_break(sym_name):
 
     bp.delete()
 
+
 def run_test():
     "Run through the tests one by one"
 
@@ -57,28 +50,5 @@ def run_test():
     # finally check we don't barf inspecting registers
     gdb.execute("info registers")
 
-#
-# This runs as the script it sourced (via -x, via run-test.py)
-#
-try:
-    inferior = gdb.selected_inferior()
-    arch = inferior.architecture()
-    print("ATTACHED: %s" % arch.name())
-except (gdb.error, AttributeError):
-    print("SKIPPING (not connected)", file=sys.stderr)
-    exit(0)
-
-if gdb.parse_and_eval('$pc') == 0:
-    print("SKIP: PC not set")
-    exit(0)
-
-try:
-    # Run the actual tests
-    run_test()
-except (gdb.error):
-    print ("GDB Exception: %s" % (sys.exc_info()[0]))
-    failcount += 1
-    pass
-
-print("All tests complete: %d failures" % failcount)
-exit(failcount)
+
+main(run_test)
diff --git a/tests/tcg/multiarch/gdbstub/test-proc-mappings.py b/tests/tcg/multiarch/gdbstub/test-proc-mappings.py
index 04ec61d2197..564613fabf0 100644
--- a/tests/tcg/multiarch/gdbstub/test-proc-mappings.py
+++ b/tests/tcg/multiarch/gdbstub/test-proc-mappings.py
@@ -3,20 +3,7 @@
 This runs as a sourced script (via -x, via run-test.py)."""
 from __future__ import print_function
 import gdb
-import sys
-
-
-n_failures = 0
-
-
-def report(cond, msg):
-    """Report success/fail of a test"""
-    if cond:
-        print("PASS: {}".format(msg))
-    else:
-        print("FAIL: {}".format(msg))
-        global n_failures
-        n_failures += 1
+from test_gdbstub import main, report
 
 
 def run_test():
@@ -37,26 +24,4 @@ def run_test():
     # report("/sha1" in mappings, "Found the test binary name in the mappings")
 
 
-def main():
-    """Prepare the environment and run through the tests"""
-    try:
-        inferior = gdb.selected_inferior()
-        print("ATTACHED: {}".format(inferior.architecture().name()))
-    except (gdb.error, AttributeError):
-        print("SKIPPING (not connected)")
-        exit(0)
-
-    if gdb.parse_and_eval('$pc') == 0:
-        print("SKIP: PC not set")
-        exit(0)
-
-    try:
-        # Run the actual tests
-        run_test()
-    except gdb.error:
-        report(False, "GDB Exception: {}".format(sys.exc_info()[0]))
-    print("All tests complete: %d failures" % n_failures)
-    exit(n_failures)
-
-
-main()
+main(run_test)
diff --git a/tests/tcg/multiarch/gdbstub/test-qxfer-auxv-read.py b/tests/tcg/multiarch/gdbstub/test-qxfer-auxv-read.py
index 926fa962b77..00c26ab4a95 100644
--- a/tests/tcg/multiarch/gdbstub/test-qxfer-auxv-read.py
+++ b/tests/tcg/multiarch/gdbstub/test-qxfer-auxv-read.py
@@ -6,18 +6,8 @@
 #
 
 import gdb
-import sys
+from test_gdbstub import main, report
 
-failcount = 0
-
-def report(cond, msg):
-    "Report success/fail of test"
-    if cond:
-        print ("PASS: %s" % (msg))
-    else:
-        print ("FAIL: %s" % (msg))
-        global failcount
-        failcount += 1
 
 def run_test():
     "Run through the tests one by one"
@@ -26,28 +16,5 @@ def run_test():
     report(isinstance(auxv, str), "Fetched auxv from inferior")
     report(auxv.find("sha1"), "Found test binary name in auxv")
 
-#
-# This runs as the script it sourced (via -x, via run-test.py)
-#
-try:
-    inferior = gdb.selected_inferior()
-    arch = inferior.architecture()
-    print("ATTACHED: %s" % arch.name())
-except (gdb.error, AttributeError):
-    print("SKIPPING (not connected)", file=sys.stderr)
-    exit(0)
-
-if gdb.parse_and_eval('$pc') == 0:
-    print("SKIP: PC not set")
-    exit(0)
-
-try:
-    # Run the actual tests
-    run_test()
-except (gdb.error):
-    print ("GDB Exception: %s" % (sys.exc_info()[0]))
-    failcount += 1
-    pass
 
-print("All tests complete: %d failures" % failcount)
-exit(failcount)
+main(run_test)
diff --git a/tests/tcg/multiarch/gdbstub/test-thread-breakpoint.py b/tests/tcg/multiarch/gdbstub/test-thread-breakpoint.py
index e57d2a8db8b..4d6b6b9fbe7 100644
--- a/tests/tcg/multiarch/gdbstub/test-thread-breakpoint.py
+++ b/tests/tcg/multiarch/gdbstub/test-thread-breakpoint.py
@@ -6,18 +6,8 @@
 #
 
 import gdb
-import sys
+from test_gdbstub import main, report
 
-failcount = 0
-
-def report(cond, msg):
-    "Report success/fail of test"
-    if cond:
-        print ("PASS: %s" % (msg))
-    else:
-        print ("FAIL: %s" % (msg))
-        global failcount
-        failcount += 1
 
 def run_test():
     "Run through the tests one by one"
@@ -29,28 +19,5 @@ def run_test():
     frame = gdb.selected_frame()
     report(str(frame.function()) == "thread1_func", "break @ %s"%frame)
 
-#
-# This runs as the script it sourced (via -x, via run-test.py)
-#
-try:
-    inferior = gdb.selected_inferior()
-    arch = inferior.architecture()
-    print("ATTACHED: %s" % arch.name())
-except (gdb.error, AttributeError):
-    print("SKIPPING (not connected)", file=sys.stderr)
-    exit(0)
-
-if gdb.parse_and_eval('$pc') == 0:
-    print("SKIP: PC not set")
-    exit(0)
-
-try:
-    # Run the actual tests
-    run_test()
-except (gdb.error):
-    print ("GDB Exception: %s" % (sys.exc_info()[0]))
-    failcount += 1
-    pass
 
-print("All tests complete: %d failures" % failcount)
-exit(failcount)
+main(run_test)
diff --git a/tests/tcg/s390x/gdbstub/test-signals-s390x.py b/tests/tcg/s390x/gdbstub/test-signals-s390x.py
index ca2bbc0b03e..b6b7b39fc46 100644
--- a/tests/tcg/s390x/gdbstub/test-signals-s390x.py
+++ b/tests/tcg/s390x/gdbstub/test-signals-s390x.py
@@ -7,19 +7,7 @@
 #
 
 import gdb
-import sys
-
-failcount = 0
-
-
-def report(cond, msg):
-    """Report success/fail of test"""
-    if cond:
-        print("PASS: %s" % (msg))
-    else:
-        print("FAIL: %s" % (msg))
-        global failcount
-        failcount += 1
+from test_gdbstub import main, report
 
 
 def run_test():
@@ -42,31 +30,7 @@ def run_test():
     gdb.Breakpoint("_exit")
     gdb.execute("c")
     status = int(gdb.parse_and_eval("$r2"))
-    report(status == 0, "status == 0");
-
-
-#
-# This runs as the script it sourced (via -x, via run-test.py)
-#
-try:
-    inferior = gdb.selected_inferior()
-    arch = inferior.architecture()
-    print("ATTACHED: %s" % arch.name())
-except (gdb.error, AttributeError):
-    print("SKIPPING (not connected)", file=sys.stderr)
-    exit(0)
-
-if gdb.parse_and_eval("$pc") == 0:
-    print("SKIP: PC not set")
-    exit(0)
+    report(status == 0, "status == 0")
 
-try:
-    # Run the actual tests
-    run_test()
-except (gdb.error):
-    print("GDB Exception: %s" % (sys.exc_info()[0]))
-    failcount += 1
-    pass
 
-print("All tests complete: %d failures" % failcount)
-exit(failcount)
+main(run_test)
diff --git a/tests/tcg/s390x/gdbstub/test-svc.py b/tests/tcg/s390x/gdbstub/test-svc.py
index 804705fede9..17210b4e020 100644
--- a/tests/tcg/s390x/gdbstub/test-svc.py
+++ b/tests/tcg/s390x/gdbstub/test-svc.py
@@ -3,20 +3,7 @@
 This runs as a sourced script (via -x, via run-test.py)."""
 from __future__ import print_function
 import gdb
-import sys
-
-
-n_failures = 0
-
-
-def report(cond, msg):
-    """Report success/fail of a test"""
-    if cond:
-        print("PASS: {}".format(msg))
-    else:
-        print("FAIL: {}".format(msg))
-        global n_failures
-        n_failures += 1
+from test_gdbstub import main, report
 
 
 def run_test():
@@ -35,26 +22,4 @@ def run_test():
     gdb.execute("si")
 
 
-def main():
-    """Prepare the environment and run through the tests"""
-    try:
-        inferior = gdb.selected_inferior()
-        print("ATTACHED: {}".format(inferior.architecture().name()))
-    except (gdb.error, AttributeError):
-        print("SKIPPING (not connected)")
-        exit(0)
-
-    if gdb.parse_and_eval('$pc') == 0:
-        print("SKIP: PC not set")
-        exit(0)
-
-    try:
-        # Run the actual tests
-        run_test()
-    except gdb.error:
-        report(False, "GDB Exception: {}".format(sys.exc_info()[0]))
-    print("All tests complete: %d failures" % n_failures)
-    exit(n_failures)
-
-
-main()
+main(run_test)
-- 
2.43.0

[PATCH v4 3/3] tests/tcg: Add the PROT_NONE gdbstub test

[Ilya Leoshkevich]

Make sure that qemu gdbstub, like gdbserver, allows reading from and
writing to PROT_NONE pages.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 tests/tcg/multiarch/Makefile.target      |  9 +++++-
 tests/tcg/multiarch/gdbstub/prot-none.py | 36 +++++++++++++++++++++
 tests/tcg/multiarch/prot-none.c          | 40 ++++++++++++++++++++++++
 3 files changed, 84 insertions(+), 1 deletion(-)
 create mode 100644 tests/tcg/multiarch/gdbstub/prot-none.py
 create mode 100644 tests/tcg/multiarch/prot-none.c

diff --git a/tests/tcg/multiarch/Makefile.target b/tests/tcg/multiarch/Makefile.target
index d31ba8d6ae4..315a2e13588 100644
--- a/tests/tcg/multiarch/Makefile.target
+++ b/tests/tcg/multiarch/Makefile.target
@@ -101,13 +101,20 @@ run-gdbstub-registers: sha512
 		--bin $< --test $(MULTIARCH_SRC)/gdbstub/registers.py, \
 	checking register enumeration)
 
+run-gdbstub-prot-none: prot-none
+	$(call run-test, $@, env PROT_NONE_PY=1 $(GDB_SCRIPT) \
+		--gdb $(GDB) \
+		--qemu $(QEMU) --qargs "$(QEMU_OPTS)" \
+		--bin $< --test $(MULTIARCH_SRC)/gdbstub/prot-none.py, \
+	accessing PROT_NONE memory)
+
 else
 run-gdbstub-%:
 	$(call skip-test, "gdbstub test $*", "need working gdb with $(patsubst -%,,$(TARGET_NAME)) support")
 endif
 EXTRA_RUNS += run-gdbstub-sha1 run-gdbstub-qxfer-auxv-read \
 	      run-gdbstub-proc-mappings run-gdbstub-thread-breakpoint \
-	      run-gdbstub-registers
+	      run-gdbstub-registers run-gdbstub-prot-none
 
 # ARM Compatible Semi Hosting Tests
 #
diff --git a/tests/tcg/multiarch/gdbstub/prot-none.py b/tests/tcg/multiarch/gdbstub/prot-none.py
new file mode 100644
index 00000000000..e829d3ebc5f
--- /dev/null
+++ b/tests/tcg/multiarch/gdbstub/prot-none.py
@@ -0,0 +1,36 @@
+"""Test that GDB can access PROT_NONE pages.
+
+This runs as a sourced script (via -x, via run-test.py).
+
+SPDX-License-Identifier: GPL-2.0-or-later
+"""
+import ctypes
+from test_gdbstub import main, report
+
+
+def probe_proc_self_mem():
+    buf = ctypes.create_string_buffer(b'aaa')
+    try:
+        with open("/proc/self/mem", "rb") as fp:
+            fp.seek(ctypes.addressof(buf))
+            return fp.read(3) == b'aaa'
+    except OSError:
+        return False
+
+
+def run_test():
+    """Run through the tests one by one"""
+    if not probe_proc_self_mem:
+        print("SKIP: /proc/self/mem is not usable")
+        exit(0)
+    gdb.Breakpoint("break_here")
+    gdb.execute("continue")
+    val = gdb.parse_and_eval("*(char[2] *)q").string()
+    report(val == "42", "{} == 42".format(val))
+    gdb.execute("set *(char[3] *)q = \"24\"")
+    gdb.execute("continue")
+    exitcode = int(gdb.parse_and_eval("$_exitcode"))
+    report(exitcode == 0, "{} == 0".format(exitcode))
+
+
+main(run_test)
diff --git a/tests/tcg/multiarch/prot-none.c b/tests/tcg/multiarch/prot-none.c
new file mode 100644
index 00000000000..dc56aadb3c5
--- /dev/null
+++ b/tests/tcg/multiarch/prot-none.c
@@ -0,0 +1,40 @@
+/*
+ * Test that GDB can access PROT_NONE pages.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+void break_here(void *q)
+{
+}
+
+int main(void)
+{
+    long pagesize = sysconf(_SC_PAGESIZE);
+    void *p, *q;
+    int err;
+
+    p = mmap(NULL, pagesize * 2, PROT_READ | PROT_WRITE,
+             MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+    assert(p != MAP_FAILED);
+    q = p + pagesize - 1;
+    strcpy(q, "42");
+
+    err = mprotect(p, pagesize * 2, PROT_NONE);
+    assert(err == 0);
+
+    break_here(q);
+
+    err = mprotect(p, pagesize * 2, PROT_READ);
+    assert(err == 0);
+    if (getenv("PROT_NONE_PY")) {
+        assert(strcmp(q, "24") == 0);
+    }
+
+    return EXIT_SUCCESS;
+}
-- 
2.43.0

Re: [PATCH v4 0/3] linux-user: Allow gdbstub to ignore page protection

[Richard Henderson]

On 1/29/24 19:32, Ilya Leoshkevich wrote:
> v3:https://lists.gnu.org/archive/html/qemu-devel/2024-01/msg02907.html
> v3 -> v4: Hide InteractiveConsole behind QEMU_TEST_INTERACTIVE (Alex).
>            Probe /proc/self/mem in the PROT_NONE test.
> 
> v2:https://lists.gnu.org/archive/html/qemu-devel/2024-01/msg01592.html
> v2 -> v3: Add Richard's R-b on [1/3].
>            Fix printing the architecture name and the number of failures
>            in test_gdbstub.py.
>            Patches that need review: [2/3] and [3/3].
> 
> v1:https://lists.gnu.org/archive/html/qemu-devel/2024-01/msg01314.html
> v1 -> v2: Use /proc/self/mem as a fallback. Handle TB invalidation
>            (Richard).
>            Test cross-page accesses.
> 
> RFC:https://lists.gnu.org/archive/html/qemu-devel/2023-12/msg02044.html
> RFC -> v1: Use /proc/self/mem and accept that this will not work
>             without /proc.
>             Factor out a couple functions for gdbstub testing.
>             Add a test.

Thanks, updated tcg-next with this replacement.


r~

Re: [PATCH v4 2/3] tests/tcg: Factor out gdbstub test functions

[Alex Bennée]

Ilya Leoshkevich <iii@linux.ibm.com> writes:

> Both the report() function as well as the initial gdbstub test sequence
> are copy-pasted into ~10 files with slight modifications. This
> indicates that they are indeed generic, so factor them out. While
> at it, add a few newlines to make the formatting closer to PEP-8.
>
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro

Re: [PATCH v4 3/3] tests/tcg: Add the PROT_NONE gdbstub test

[Alex Bennée]

Ilya Leoshkevich <iii@linux.ibm.com> writes:

> Make sure that qemu gdbstub, like gdbserver, allows reading from and
> writing to PROT_NONE pages.
>
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>

Acked-by: Alex Bennée <alex.bennee@linaro.org>


-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro