Re: [PATCH 3/3] drm/panic: Add a kconfig option to dump kunits results to png

[Jocelyn Falempe <jfalempe@redhat.com>]

On 27/08/2025 12:45, Thomas Zimmermann wrote:
> Hi
> 
> Am 21.08.25 um 11:49 schrieb Jocelyn Falempe:
>> This is a bit hacky, but very handy if you want to customize the
>> panic screen.
>> It allows to dump the generated images to the logs, and then a python
>> script can convert it to .png files. It makes it easy to check how
>> the panic screen will look on different resolutions, without having
>> to crash a VM.
>> To not pollute the logs, it uses a monochrome framebuffer, compress
>> it with zlib, and base64 encode it.
> 
> May I suggest to export the raw image via debugfs? Debugfs can also 
> export additional information in additional files, such as width/height/ 
> stride/format. This could provide the real/last image on the fly, simply 
> by reading the files. No workarounds or encodings needed.

I'm looking into that. The difficulty is to get the debugfs content 
outside of the test kernel. As I'm using a uml kernel for testing, I 
will need a special initrd, and a way to share files with the host.

Best regards,

-- 

Jocelyn
> 
> Best regards
> Thomas
> 
>>
>> Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
>> ---
>>   drivers/gpu/drm/Kconfig.debug          |  14 ++++
>>   drivers/gpu/drm/tests/drm_panic_test.c | 111 +++++++++++++++++++++++++
>>   scripts/kunitpanic2png.py              |  53 ++++++++++++
>>   3 files changed, 178 insertions(+)
>>   create mode 100755 scripts/kunitpanic2png.py
>>
>> diff --git a/drivers/gpu/drm/Kconfig.debug b/drivers/gpu/drm/ 
>> Kconfig.debug
>> index 05dc43c0b8c5..d8ae85132d32 100644
>> --- a/drivers/gpu/drm/Kconfig.debug
>> +++ b/drivers/gpu/drm/Kconfig.debug
>> @@ -84,6 +84,20 @@ config DRM_KUNIT_TEST
>>         If in doubt, say "N".
>> +config DRM_PANIC_KUNIT_TEST_DUMP
>> +    bool "Enable screen dump to logs in KUnit tests for drm_panic"
>> +    default n
>> +    depends on DRM && DRM_PANIC && DRM_KUNIT_TEST
>> +    select ZLIB_DEFLATE
>> +    help
>> +      This allows to dump the panic screen to the KUnit tests logs.
>> +      It's possible with a small python script to write pngs from the 
>> logs.
>> +
>> +      This is only to help developers customizing the drm_panic screen,
>> +      checking the result for different resolutions.
>> +
>> +      If in doubt, say "N"
>> +
>>   config DRM_TTM_KUNIT_TEST
>>       tristate "KUnit tests for TTM" if !KUNIT_ALL_TESTS
>>       default n
>> diff --git a/drivers/gpu/drm/tests/drm_panic_test.c b/drivers/gpu/drm/ 
>> tests/drm_panic_test.c
>> index 46ff3e5e0e5d..8cddb845aea9 100644
>> --- a/drivers/gpu/drm/tests/drm_panic_test.c
>> +++ b/drivers/gpu/drm/tests/drm_panic_test.c
>> @@ -115,24 +115,135 @@ static void 
>> drm_test_panic_screen_user_page(struct kunit *test)
>>       kfree(pages);
>>   }
>> +#ifdef CONFIG_DRM_PANIC_KUNIT_TEST_DUMP
>> +#include <linux/base64.h>
>> +#include <linux/delay.h>
>> +#include <linux/zlib.h>
>> +
>> +#define LINE_LEN 128
>> +
>> +#define COMPR_LEVEL 6
>> +#define WINDOW_BITS 12
>> +#define MEM_LEVEL 4
>> +
>> +static int compress_image(u8 *src, int size, u8 *dst)
>> +{
>> +    struct z_stream_s stream;
>> +
>> +    stream.workspace = 
>> kmalloc(zlib_deflate_workspacesize(WINDOW_BITS, MEM_LEVEL),
>> +                   GFP_KERNEL);
>> +
>> +    if (zlib_deflateInit2(&stream, COMPR_LEVEL, Z_DEFLATED, WINDOW_BITS,
>> +                  MEM_LEVEL, Z_DEFAULT_STRATEGY) != Z_OK)
>> +        return -EINVAL;
>> +
>> +    stream.next_in = src;
>> +    stream.avail_in = size;
>> +    stream.total_in = 0;
>> +    stream.next_out = dst;
>> +    stream.avail_out = size;
>> +    stream.total_out = 0;
>> +
>> +    if (zlib_deflate(&stream, Z_FINISH) != Z_STREAM_END)
>> +        return -EINVAL;
>> +
>> +    if (zlib_deflateEnd(&stream) != Z_OK)
>> +        return -EINVAL;
>> +
>> +    kfree(stream.workspace);
>> +
>> +    return stream.total_out;
>> +}
>> +
>> +static void dump_image(u8 *fb, unsigned int width, unsigned int height)
>> +{
>> +    int len = 0;
>> +    char *dst;
>> +    char *compressed;
>> +    int sent = 0;
>> +    int stride = DIV_ROUND_UP(width, 8);
>> +    int size = stride * height;
>> +
>> +    compressed = vzalloc(size);
>> +    if (!compressed)
>> +        return;
>> +    len = compress_image(fb, size, compressed);
>> +    if (len < 0) {
>> +        pr_err("Compression failed %d", len);
>> +        return;
>> +    }
>> +
>> +    dst = vzalloc(4 * DIV_ROUND_UP(len, 3) + 1);
>> +    if (!dst)
>> +        return;
>> +
>> +    len = base64_encode(compressed, len, dst);
>> +
>> +    pr_info("KUNIT PANIC IMAGE DUMP START %dx%d", width, height);
>> +    while (len > 0) {
>> +        char save = dst[sent + LINE_LEN];
>> +
>> +        dst[sent + LINE_LEN] = 0;
>> +        pr_info("%s", dst + sent);
>> +        dst[sent + LINE_LEN] = save;
>> +        sent += LINE_LEN;
>> +        len -= LINE_LEN;
>> +    }
>> +    pr_info("KUNIT PANIC IMAGE DUMP END");
>> +    vfree(compressed);
>> +    vfree(dst);
>> +
>> +}
>> +
>> +// Ignore pixel format, use 1bit per pixel in monochrome.
>>   static void drm_test_panic_set_pixel(struct drm_scanout_buffer *sb,
>>                        unsigned int x,
>>                        unsigned int y,
>>                        u32 color)
>>   {
>> +    int stride = DIV_ROUND_UP(sb->width, 8);
>> +    size_t off = x / 8 + y * stride;
>> +    u8 shift = 7 - (x % 8);
>> +    u8 *fb = (u8 *) sb->private;
>> +
>> +    if (color)
>> +        fb[off] |= 1 << shift;
>> +    else
>> +        fb[off] &= ~(1 << shift);
>>   }
>> +#else
>> +static void dump_image(u8 *fb, unsigned int width, unsigned int 
>> height) {}
>> +static void drm_test_panic_set_pixel(struct drm_scanout_buffer *sb,
>> +                     unsigned int x,
>> +                     unsigned int y,
>> +                     u32 color)
>> +{
>> +}
>> +#endif
>> +
>>   static void drm_test_panic_screen_user_set_pixel(struct kunit *test)
>>   {
>>       struct drm_scanout_buffer *sb = test->priv;
>>       const struct drm_test_mode *params = test->param_value;
>> +    int fb_size;
>> +    u8 *fb;
>>       sb->format = drm_format_info(params->format);
>> +    fb_size = DIV_ROUND_UP(params->width, 8) * params->height;
>> +
>> +    fb = vzalloc(fb_size);
>> +    KUNIT_ASSERT_NOT_NULL(test, fb);
>> +    sb->private = fb;
>>       sb->set_pixel = drm_test_panic_set_pixel;
>>       sb->width = params->width;
>>       sb->height = params->height;
>>       params->draw_screen(sb);
>> +    if (params->format == DRM_FORMAT_XRGB8888)
>> +        dump_image(fb, sb->width, sb->height);
>> +
>> +    vfree(fb);
>>   }
>>   static void drm_test_panic_desc(const struct drm_test_mode *t, char 
>> *desc)
>> diff --git a/scripts/kunitpanic2png.py b/scripts/kunitpanic2png.py
>> new file mode 100755
>> index 000000000000..e292afd7422c
>> --- /dev/null
>> +++ b/scripts/kunitpanic2png.py
>> @@ -0,0 +1,53 @@
>> +#!/usr/bin/env python3
>> +# SPDX-License-Identifier: MIT
>> +#
>> +# Copyright (c) 2025 Red Hat.
>> +# Author: Jocelyn Falempe <jfalempe@redhat.com>
>> +
>> +from argparse import ArgumentParser
>> +from PIL import Image
>> +import base64
>> +import zlib
>> +
>> +def get_dim(s):
>> +    (w, h) = s.split('x')
>> +    return (int(w), int(h))
>> +
>> +def draw_image(img_data, width, height, n_img):
>> +
>> +    decoded = base64.b64decode(img_data)
>> +    unzipped = zlib.decompress(decoded)
>> +
>> +    img = Image.frombytes("1", (width, height), unzipped)
>> +    fname = f"panic_screen_{n_img}.png"
>> +    img.save(fname)
>> +    print(f"Image {width}x{height} saved to {fname}")
>> +
>> +def main():
>> +    parser = ArgumentParser(
>> +        prog="kunitpanic2png",
>> +        description="Read drm_panic kunit logs and translate that to 
>> png files")
>> +
>> +    parser.add_argument("filename", help="log file from kunit, 
>> usually test.log")
>> +
>> +    parsing_img = False
>> +    img_data = ""
>> +    n_img = 0
>> +
>> +    args = parser.parse_args()
>> +    with open(args.filename, "r") as f:
>> +        for line in f.readlines():
>> +            if line.startswith("KUNIT PANIC IMAGE DUMP START"):
>> +                parsing_img = True
>> +                width, height = get_dim(line.split()[-1])
>> +                continue
>> +            if line.startswith("KUNIT PANIC IMAGE DUMP END"):
>> +                draw_image(img_data, width, height, n_img)
>> +                parsing_img = False
>> +                img_data = ""
>> +                n_img += 1
>> +                continue
>> +            if parsing_img:
>> +                img_data += line.strip()
>> +
>> +main()
>