[PATCH v4 0/2] kunit: qemu_configs: Add MIPS configurations

[Thomas Weißschuh]

Add basic support to run various MIPS variants via kunit_tool using the
virtualized malta platform.

Signed-off-by: Thomas Weißschuh <thomas.w...@linutronix.de>
---
Changes in v4:
- Rebase on v6.16-rc1
- Pick up reviews from David
- Clarify that GIC page is linked to vDSO
- Link to v3: https://lore.kernel.org/r/20250415-kunit-mip...@linutronix.de

Changes in v3:
- Also skip VDSO_RANDOMIZE_SIZE adjustment for kthreads
- Link to v2: https://lore.kernel.org/r/20250414-kunit-mip...@linutronix.de

Changes in v2:
- Fix usercopy kunit test by handling ABI-less tasks in stack_top()
- Drop change to mm initialization.
The broken test is not built by default anymore.
- Link to v1: https://lore.kernel.org/r/20250212-kunit-mip...@linutronix.de

---
Thomas Weißschuh (2):
MIPS: Don't crash in stack_top() for tasks without ABI or vDSO
kunit: qemu_configs: Add MIPS configurations

arch/mips/kernel/process.c | 16 +++++++++-------
tools/testing/kunit/qemu_configs/mips.py | 18 ++++++++++++++++++
tools/testing/kunit/qemu_configs/mips64.py | 19 +++++++++++++++++++
tools/testing/kunit/qemu_configs/mips64el.py | 19 +++++++++++++++++++
tools/testing/kunit/qemu_configs/mipsel.py | 18 ++++++++++++++++++
5 files changed, 83 insertions(+), 7 deletions(-)
---
base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494
change-id: 20241014-kunit-mips-e4fe1c265ed7

Best regards,
--
Thomas Weißschuh <thomas.w...@linutronix.de>

[Thomas Weißschuh]

Not all tasks have an ABI associated or vDSO mapped,
for example kthreads never do.
If such a task ever ends up calling stack_top(), it will derefence the
NULL ABI pointer and crash.

This can for example happen when using kunit:

mips_stack_top+0x28/0xc0
arch_pick_mmap_layout+0x190/0x220
kunit_vm_mmap_init+0xf8/0x138
__kunit_add_resource+0x40/0xa8
kunit_vm_mmap+0x88/0xd8
usercopy_test_init+0xb8/0x240
kunit_try_run_case+0x5c/0x1a8
kunit_generic_run_threadfn_adapter+0x28/0x50
kthread+0x118/0x240
ret_from_kernel_thread+0x14/0x1c

Only dereference the ABI point if it is set.

The GIC page is also included as it is specific to the vDSO.
Also move the randomization adjustment into the same conditional.

Signed-off-by: Thomas Weißschuh <thomas.w...@linutronix.de>
Reviewed-by: David Gow <davi...@google.com>
---
arch/mips/kernel/process.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index b630604c577f9ff3f2493b0f254363e499c8318c..02aa6a04a21da437909eeac4f149155cc298f5b5 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -690,18 +690,20 @@ unsigned long mips_stack_top(void)
}

/* Space for the VDSO, data page & GIC user page */
- top -= PAGE_ALIGN(current->thread.abi->vdso->size);
- top -= PAGE_SIZE;
- top -= mips_gic_present() ? PAGE_SIZE : 0;
+ if (current->thread.abi) {
+ top -= PAGE_ALIGN(current->thread.abi->vdso->size);
+ top -= PAGE_SIZE;
+ top -= mips_gic_present() ? PAGE_SIZE : 0;
+
+ /* Space to randomize the VDSO base */
+ if (current->flags & PF_RANDOMIZE)
+ top -= VDSO_RANDOMIZE_SIZE;
+ }

/* Space for cache colour alignment */
if (cpu_has_dc_aliases)
top -= shm_align_mask + 1;

- /* Space to randomize the VDSO base */
- if (current->flags & PF_RANDOMIZE)
- top -= VDSO_RANDOMIZE_SIZE;
-
return top;
}


--
2.49.0

[Thomas Weißschuh]

Add basic support to run various MIPS variants via kunit_tool using the
virtualized malta platform.

Signed-off-by: Thomas Weißschuh <thomas.w...@linutronix.de>

Reviewed-by: David Gow <davi...@google.com>
---

tools/testing/kunit/qemu_configs/mips.py | 18 ++++++++++++++++++
tools/testing/kunit/qemu_configs/mips64.py | 19 +++++++++++++++++++
tools/testing/kunit/qemu_configs/mips64el.py | 19 +++++++++++++++++++
tools/testing/kunit/qemu_configs/mipsel.py | 18 ++++++++++++++++++

4 files changed, 74 insertions(+)

diff --git a/tools/testing/kunit/qemu_configs/mips.py b/tools/testing/kunit/qemu_configs/mips.py
new file mode 100644
index 0000000000000000000000000000000000000000..8899ac157b30bd2ee847eacd5b90fe6ad4e5fb04
--- /dev/null
+++ b/tools/testing/kunit/qemu_configs/mips.py
@@ -0,0 +1,18 @@
+# SPDX-License-Identifier: GPL-2.0
+
+from ..qemu_config import QemuArchParams
+
+QEMU_ARCH = QemuArchParams(linux_arch='mips',
+ kconfig='''
+CONFIG_32BIT=y
+CONFIG_CPU_BIG_ENDIAN=y
+CONFIG_MIPS_MALTA=y
+CONFIG_SERIAL_8250=y
+CONFIG_SERIAL_8250_CONSOLE=y
+CONFIG_POWER_RESET=y
+CONFIG_POWER_RESET_SYSCON=y
+''',
+ qemu_arch='mips',
+ kernel_path='vmlinuz',
+ kernel_command_line='console=ttyS0',
+ extra_qemu_params=['-M', 'malta'])
diff --git a/tools/testing/kunit/qemu_configs/mips64.py b/tools/testing/kunit/qemu_configs/mips64.py
new file mode 100644
index 0000000000000000000000000000000000000000..1478aed05b94da4914f34c6a8affdcfe34eb88ea
--- /dev/null
+++ b/tools/testing/kunit/qemu_configs/mips64.py
@@ -0,0 +1,19 @@
+# SPDX-License-Identifier: GPL-2.0
+
+from ..qemu_config import QemuArchParams
+
+QEMU_ARCH = QemuArchParams(linux_arch='mips',
+ kconfig='''
+CONFIG_CPU_MIPS64_R2=y
+CONFIG_64BIT=y
+CONFIG_CPU_BIG_ENDIAN=y
+CONFIG_MIPS_MALTA=y
+CONFIG_SERIAL_8250=y
+CONFIG_SERIAL_8250_CONSOLE=y
+CONFIG_POWER_RESET=y
+CONFIG_POWER_RESET_SYSCON=y
+''',
+ qemu_arch='mips64',
+ kernel_path='vmlinuz',
+ kernel_command_line='console=ttyS0',
+ extra_qemu_params=['-M', 'malta', '-cpu', '5KEc'])
diff --git a/tools/testing/kunit/qemu_configs/mips64el.py b/tools/testing/kunit/qemu_configs/mips64el.py
new file mode 100644
index 0000000000000000000000000000000000000000..300c711d7a82500b2ebcb4cf1467b6f72b5c17aa
--- /dev/null
+++ b/tools/testing/kunit/qemu_configs/mips64el.py
@@ -0,0 +1,19 @@
+# SPDX-License-Identifier: GPL-2.0
+
+from ..qemu_config import QemuArchParams
+
+QEMU_ARCH = QemuArchParams(linux_arch='mips',
+ kconfig='''
+CONFIG_CPU_MIPS64_R2=y
+CONFIG_64BIT=y
+CONFIG_CPU_LITTLE_ENDIAN=y
+CONFIG_MIPS_MALTA=y
+CONFIG_SERIAL_8250=y
+CONFIG_SERIAL_8250_CONSOLE=y
+CONFIG_POWER_RESET=y
+CONFIG_POWER_RESET_SYSCON=y
+''',
+ qemu_arch='mips64el',
+ kernel_path='vmlinuz',
+ kernel_command_line='console=ttyS0',
+ extra_qemu_params=['-M', 'malta', '-cpu', '5KEc'])
diff --git a/tools/testing/kunit/qemu_configs/mipsel.py b/tools/testing/kunit/qemu_configs/mipsel.py
new file mode 100644
index 0000000000000000000000000000000000000000..3d3543315b45776d0e77fb5c00c8c0a89eafdffd
--- /dev/null
+++ b/tools/testing/kunit/qemu_configs/mipsel.py
@@ -0,0 +1,18 @@
+# SPDX-License-Identifier: GPL-2.0
+
+from ..qemu_config import QemuArchParams
+
+QEMU_ARCH = QemuArchParams(linux_arch='mips',
+ kconfig='''
+CONFIG_32BIT=y
+CONFIG_CPU_LITTLE_ENDIAN=y
+CONFIG_MIPS_MALTA=y
+CONFIG_SERIAL_8250=y
+CONFIG_SERIAL_8250_CONSOLE=y
+CONFIG_POWER_RESET=y
+CONFIG_POWER_RESET_SYSCON=y
+''',
+ qemu_arch='mipsel',
+ kernel_path='vmlinuz',
+ kernel_command_line='console=ttyS0',
+ extra_qemu_params=['-M', 'malta'])

--
2.49.0

[Huacai Chen]

Reviewed-by: Huacai Chen <chenh...@loongson.cn>

[Thomas Bogendoerfer]

On Wed, Jun 11, 2025 at 01:28:26PM +0200, Thomas Weißschuh wrote:
> Not all tasks have an ABI associated or vDSO mapped,
> for example kthreads never do.
> If such a task ever ends up calling stack_top(), it will derefence the
> NULL ABI pointer and crash.
>
> This can for example happen when using kunit:
>
> mips_stack_top+0x28/0xc0
> arch_pick_mmap_layout+0x190/0x220
> kunit_vm_mmap_init+0xf8/0x138
> __kunit_add_resource+0x40/0xa8
> kunit_vm_mmap+0x88/0xd8
> usercopy_test_init+0xb8/0x240
> kunit_try_run_case+0x5c/0x1a8
> kunit_generic_run_threadfn_adapter+0x28/0x50
> kthread+0x118/0x240
> ret_from_kernel_thread+0x14/0x1c
>
> Only dereference the ABI point if it is set.
>
> The GIC page is also included as it is specific to the vDSO.
> Also move the randomization adjustment into the same conditional.
>
> Signed-off-by: Thomas Weißschuh <thomas.w...@linutronix.de>
> Reviewed-by: David Gow <davi...@google.com>
> ---
> arch/mips/kernel/process.c | 16 +++++++++-------
> 1 file changed, 9 insertions(+), 7 deletions(-)

applied to mips-next.

Thomas.

--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]