1. Patchew
  2. QEMU
  3. [PATCH v3 0/3] linux-user: Allow gdbstub to ignore page protection
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[PATCH v3 3/3] tests/tcg: Add the PROT_NONE gdbstub test

Ilya Leoshkevich posted 3 patches 2 years ago
Maintainers: Richard Henderson <richard.henderson@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>, Peter Maydell <peter.maydell@linaro.org>, "Alex Bennée" <alex.bennee@linaro.org>, "Philippe Mathieu-Daudé" <philmd@linaro.org>, David Hildenbrand <david@redhat.com>, Ilya Leoshkevich <iii@linux.ibm.com>
There is a newer version of this series
[PATCH v3 3/3] tests/tcg: Add the PROT_NONE gdbstub test
Posted by Ilya Leoshkevich 2 years ago 
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 | 22 +++++++++++++
 tests/tcg/multiarch/prot-none.c          | 40 ++++++++++++++++++++++++
 3 files changed, 70 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..f1f1dd82cbe
--- /dev/null
+++ b/tests/tcg/multiarch/gdbstub/prot-none.py
@@ -0,0 +1,22 @@
+"""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
+"""
+from test_gdbstub import main, report
+
+
+def run_test():
+    """Run through the tests one by one"""
+    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 v3 3/3] tests/tcg: Add the PROT_NONE gdbstub test
Posted by Alex Bennée 2 years ago 
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>
> ---
>  tests/tcg/multiarch/Makefile.target      |  9 +++++-
>  tests/tcg/multiarch/gdbstub/prot-none.py | 22 +++++++++++++
>  tests/tcg/multiarch/prot-none.c          | 40 ++++++++++++++++++++++++
>  3 files changed, 70 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..f1f1dd82cbe
> --- /dev/null
> +++ b/tests/tcg/multiarch/gdbstub/prot-none.py
> @@ -0,0 +1,22 @@
> +"""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
> +"""
> +from test_gdbstub import main, report
> +
> +
> +def run_test():
> +    """Run through the tests one by one"""
> +    gdb.Breakpoint("break_here")
> +    gdb.execute("continue")
> +    val = gdb.parse_and_eval("*(char[2] *)q").string()

Better traceback:

  Breakpoint 1, break_here (q=0x400000802fff) at /home/alex/lsrc/qemu.git/tests/tcg/multiarch/prot-none.c:14
  14      }
  GDB Exception:
  Traceback (most recent call last):
    File "/home/alex/lsrc/qemu.git/tests/guest-debug/test_gdbstub.py", line 42, in main
      test()
    File "./tests/tcg/multiarch/gdbstub/prot-none.py", line 14, in run_test
      val = gdb.parse_and_eval("*(char[2] *)q").string()
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  gdb.MemoryError: Cannot access memory at address 0x400000802fff
  Python 3.11.2 (main, Mar 13 2023, 12:18:29) [GCC 12.2.0] on linux
  Type "help", "copyright", "credits" or "license" for more information.
  (InteractiveConsole)
  >>> 

> +    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;
> +}

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro
Re: Re: [PATCH v3 3/3] tests/tcg: Add the PROT_NONE gdbstub test
Posted by Ilya Leoshkevich 2 years ago 
On Mon, Jan 22, 2024 at 03:54:32PM +0000, Alex Bennée wrote:
> 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>
> > ---
> >  tests/tcg/multiarch/Makefile.target      |  9 +++++-
> >  tests/tcg/multiarch/gdbstub/prot-none.py | 22 +++++++++++++
> >  tests/tcg/multiarch/prot-none.c          | 40 ++++++++++++++++++++++++
> >  3 files changed, 70 insertions(+), 1 deletion(-)
> >  create mode 100644 tests/tcg/multiarch/gdbstub/prot-none.py
> >  create mode 100644 tests/tcg/multiarch/prot-none.c

[...]

> > +def run_test():
> > +    """Run through the tests one by one"""
> > +    gdb.Breakpoint("break_here")
> > +    gdb.execute("continue")
> > +    val = gdb.parse_and_eval("*(char[2] *)q").string()
> 
> Better traceback:
> 
>   Breakpoint 1, break_here (q=0x400000802fff) at /home/alex/lsrc/qemu.git/tests/tcg/multiarch/prot-none.c:14
>   14      }
>   GDB Exception:
>   Traceback (most recent call last):
>     File "/home/alex/lsrc/qemu.git/tests/guest-debug/test_gdbstub.py", line 42, in main
>       test()
>     File "./tests/tcg/multiarch/gdbstub/prot-none.py", line 14, in run_test
>       val = gdb.parse_and_eval("*(char[2] *)q").string()
>             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>   gdb.MemoryError: Cannot access memory at address 0x400000802fff
>   Python 3.11.2 (main, Mar 13 2023, 12:18:29) [GCC 12.2.0] on linux
>   Type "help", "copyright", "credits" or "license" for more information.
>   (InteractiveConsole)
>   >>> 

Thanks for the debug output. This shows that the feature being tested
doesn't work (the value of `q` looks sane to me). May I ask what host
distro is this? I tried on x86_64 Fedora 38 and x86_64 Ubuntu 22.04 so
far, and the test was successful.

[...]
Re: [PATCH v3 3/3] tests/tcg: Add the PROT_NONE gdbstub test
Posted by Alex Bennée 2 years ago 
Ilya Leoshkevich <iii@linux.ibm.com> writes:

> On Mon, Jan 22, 2024 at 03:54:32PM +0000, Alex Bennée wrote:
>> 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>
>> > ---
>> >  tests/tcg/multiarch/Makefile.target      |  9 +++++-
>> >  tests/tcg/multiarch/gdbstub/prot-none.py | 22 +++++++++++++
>> >  tests/tcg/multiarch/prot-none.c          | 40 ++++++++++++++++++++++++
>> >  3 files changed, 70 insertions(+), 1 deletion(-)
>> >  create mode 100644 tests/tcg/multiarch/gdbstub/prot-none.py
>> >  create mode 100644 tests/tcg/multiarch/prot-none.c
>
> [...]
>
>> > +def run_test():
>> > +    """Run through the tests one by one"""
>> > +    gdb.Breakpoint("break_here")
>> > +    gdb.execute("continue")
>> > +    val = gdb.parse_and_eval("*(char[2] *)q").string()
>> 
>> Better traceback:
>> 
>>   Breakpoint 1, break_here (q=0x400000802fff) at /home/alex/lsrc/qemu.git/tests/tcg/multiarch/prot-none.c:14
>>   14      }
>>   GDB Exception:
>>   Traceback (most recent call last):
>>     File "/home/alex/lsrc/qemu.git/tests/guest-debug/test_gdbstub.py", line 42, in main
>>       test()
>>     File "./tests/tcg/multiarch/gdbstub/prot-none.py", line 14, in run_test
>>       val = gdb.parse_and_eval("*(char[2] *)q").string()
>>             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>   gdb.MemoryError: Cannot access memory at address 0x400000802fff
>>   Python 3.11.2 (main, Mar 13 2023, 12:18:29) [GCC 12.2.0] on linux
>>   Type "help", "copyright", "credits" or "license" for more information.
>>   (InteractiveConsole)
>>   >>> 
>
> Thanks for the debug output. This shows that the feature being tested
> doesn't work (the value of `q` looks sane to me). May I ask what host
> distro is this? I tried on x86_64 Fedora 38 and x86_64 Ubuntu 22.04 so
> far, and the test was successful.

Debian Bookworm (x86_64) with gdb-multiarch installed.
>
> [...]

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro
Re: [PATCH v3 3/3] tests/tcg: Add the PROT_NONE gdbstub test
Posted by Ilya Leoshkevich 2 years ago 
On Mon, Jan 22, 2024 at 11:19:05PM +0000, Alex Bennée wrote:
> Ilya Leoshkevich <iii@linux.ibm.com> writes:
> 
> > On Mon, Jan 22, 2024 at 03:54:32PM +0000, Alex Bennée wrote:
> >> 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>
> >> > ---
> >> >  tests/tcg/multiarch/Makefile.target      |  9 +++++-
> >> >  tests/tcg/multiarch/gdbstub/prot-none.py | 22 +++++++++++++
> >> >  tests/tcg/multiarch/prot-none.c          | 40 ++++++++++++++++++++++++
> >> >  3 files changed, 70 insertions(+), 1 deletion(-)
> >> >  create mode 100644 tests/tcg/multiarch/gdbstub/prot-none.py
> >> >  create mode 100644 tests/tcg/multiarch/prot-none.c
> >
> > [...]
> >
> >> > +def run_test():
> >> > +    """Run through the tests one by one"""
> >> > +    gdb.Breakpoint("break_here")
> >> > +    gdb.execute("continue")
> >> > +    val = gdb.parse_and_eval("*(char[2] *)q").string()
> >> 
> >> Better traceback:
> >> 
> >>   Breakpoint 1, break_here (q=0x400000802fff) at /home/alex/lsrc/qemu.git/tests/tcg/multiarch/prot-none.c:14
> >>   14      }
> >>   GDB Exception:
> >>   Traceback (most recent call last):
> >>     File "/home/alex/lsrc/qemu.git/tests/guest-debug/test_gdbstub.py", line 42, in main
> >>       test()
> >>     File "./tests/tcg/multiarch/gdbstub/prot-none.py", line 14, in run_test
> >>       val = gdb.parse_and_eval("*(char[2] *)q").string()
> >>             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >>   gdb.MemoryError: Cannot access memory at address 0x400000802fff
> >>   Python 3.11.2 (main, Mar 13 2023, 12:18:29) [GCC 12.2.0] on linux
> >>   Type "help", "copyright", "credits" or "license" for more information.
> >>   (InteractiveConsole)
> >>   >>> 
> >
> > Thanks for the debug output. This shows that the feature being tested
> > doesn't work (the value of `q` looks sane to me). May I ask what host
> > distro is this? I tried on x86_64 Fedora 38 and x86_64 Ubuntu 22.04 so
> > far, and the test was successful.
> 
> Debian Bookworm (x86_64) with gdb-multiarch installed.
> >
> > [...]
> 
> -- 
> Alex Bennée
> Virtualisation Tech Lead @ Linaro

Hm, I tried that (in a VM, in case the kernel is somehow involved) and
that worked too:

  Breakpoint 1, break_here (q=0x400000802fff) at /qemu/tests/tcg/multiarch/prot-none.c:14
  14      }
  PASS: 42 == 42

I wonder what else can be different. Can it be that in your case the
test runs without /proc? Or perhaps some additional LSM is enabled?
Re: [PATCH v3 3/3] tests/tcg: Add the PROT_NONE gdbstub test
Posted by Alex Bennée 2 years ago 
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>

Hmm I'm seeing the test hang and drop to the interactive python shell:

    TEST    basic gdbstub support on aarch64
  Failed to read a valid object file image from memory.
  qemu-aarch64: QEMU: Terminated via GDBstub
    TEST    basic gdbstub qXfer:auxv:read support on aarch64
  Failed to read a valid object file image from memory.
  qemu-aarch64: QEMU: Terminated via GDBstub
    TEST    proc mappings support on aarch64
  Failed to read a valid object file image from memory.
  qemu-aarch64: QEMU: Terminated via GDBstub
    TEST    hitting a breakpoint on non-main thread on aarch64
  Failed to read a valid object file image from memory.
  qemu-aarch64: QEMU: Terminated via GDBstub
    TEST    checking register enumeration on aarch64
  Failed to read a valid object file image from memory.
  qemu-aarch64: QEMU: Terminated via GDBstub
    TEST    accessing PROT_NONE memory on aarch64
  Failed to read a valid object file image from memory.
  Python 3.11.2 (main, Mar 13 2023, 12:18:29) [GCC 12.2.0] on linux
  Type "help", "copyright", "credits" or "license" for more information.
  (InteractiveConsole)

> ---
>  tests/tcg/multiarch/Makefile.target      |  9 +++++-
>  tests/tcg/multiarch/gdbstub/prot-none.py | 22 +++++++++++++
>  tests/tcg/multiarch/prot-none.c          | 40 ++++++++++++++++++++++++
>  3 files changed, 70 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..f1f1dd82cbe
> --- /dev/null
> +++ b/tests/tcg/multiarch/gdbstub/prot-none.py
> @@ -0,0 +1,22 @@
> +"""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
> +"""
> +from test_gdbstub import main, report
> +
> +
> +def run_test():
> +    """Run through the tests one by one"""
> +    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;
> +}

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro

Patchew 2.1-devel-b67e4c2

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