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Filtering by user: aaabbb

Monday, February 26, 2024

[00:43:44] aaabbb jared: of course, you can do whatever you want with your own computer

[00:44:57] aaabbb well what do you mean by hack then?

[01:16:47] aaabbb f: ig someone could practice hacking by installing like an outdated setuid application and explore how to privesc

[01:17:07] aaabbb except j walking

[01:28:56] aaabbb also look up "ctf" sites ("capture the flag")

[10:05:35] aaabbb so i don't know about the framebuffer, but if you are doing this with the drm node, you would need DRM_IOCTL_SET_MASTER

[10:15:49] aaabbb you're right and i really only know how to do it with drm, but that's not what you're looking for

[10:25:09] aaabbb CONFIG_VT is horrible

[10:25:15] aaabbb lots of legacy code

[10:25:39] aaabbb DRM_IOCTL_SET_MASTER sets a program as the sole owner of the screen, it is an ioctl passed to /dev/dri/card0

[10:29:22] aaabbb it's Xorg that opens /dev/dri/card0 and does set master

[10:29:54] aaabbb then it does a bunch of ioctls that depend on your gpu

[10:29:59] aaabbb various things to set up pixel buffers etc

[10:32:34] aaabbb a framebuffer is waaaay easier to use than drm

[10:40:54] aaabbb BADB172: it's certainly never gonna be removed

[10:41:18] aaabbb using /dev/fb0 directly is by far the easiest and most universally supported

[11:06:50] aaabbb BADB172: linux has some very extensive and nice documentation that describes exactly how the framebufer works. most of what is printed to the framebuffer by the *kernel* is printk() calls

[11:07:05] aaabbb you can adjust that by changing the loglevel

[11:08:23] aaabbb printk(KERN_INFO, "this message will be printed at loglevel info, also, %d + %d = %d", a, b, a + b);

[11:08:33] aaabbb that kind of thing, in kernel code, will cause the message to be printed to the fb

[11:08:41] aaabbb no matter what you are doing with the fb

[11:08:41] aaabbb 3

[11:08:46] aaabbb (ignore the 3)

[11:10:41] aaabbb basically what it seems like you want is access to the framebuffer *without* a console behind it

[11:10:46] aaabbb is that it?

[11:13:11] aaabbb maybe boot with "console=/dev/null" in the kernel parameters?

[11:13:30] aaabbb what you want to do is tell the kernel not to attach the console to the framebuffer

[11:14:21] aaabbb another possibility is ioctl(fb_fd, KDSETMODE, KD_GRAPHICS)

[11:15:09] aaabbb BADB172: https://www.man7.org/linux/man-pages/man4/console_ioctl.4.html gives more info about that

[11:15:29] aaabbb setting it to graphics mode is probably preferable to murdering the console itself

[11:16:59] aaabbb yeah then you want the ioctl

[11:17:04] aaabbb on the console

[11:18:08] aaabbb i looked up "linux framebuffer disable console" and "linux fb detach console" and stuff lke that

[11:35:25] aaabbb you can change the loglevel to remove those

[11:35:43] aaabbb "strace dmesg -D" and see how it does it

[11:36:37] aaabbb syslog(6) is the syscall apparently

[11:36:55] aaabbb 6 = SYSLOG_ACTION_CONSOLE_OFF

[11:53:24] aaabbb you can prevent sysrq with kernel.sysrq i believe

[11:53:47] aaabbb that will let you set a bitmask to disable specific sysrq. ofc kernel panic will still print :p

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