Message-ID: <YuRPZX4S3DHsLeDs@angband.pl>
Date:   Fri, 29 Jul 2022 23:21:41 +0200
From:   Adam Borowski <kilobyte@...band.pl>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Xingrui Yi <yixingrui@...ux.alibaba.com>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vt: remove old FONT ioctls definitions in uapi

On Thu, Jul 28, 2022 at 10:26:10AM +0200, Greg KH wrote:
> On Fri, Jul 22, 2022 at 02:11:33PM +0800, Xingrui Yi wrote:
> > As was demonstrated by commit ff2047fb755d ("vt: drop old FONT ioctls"),
> > old font ioctls like PIO_FONT have been deleted and KDFONTOP ioctl is used
> > for years instead.
> > 
> > However, unused definitions of these ioctl numbers and "strut
> > consolefontdesc" still exist in a uapi header. They could have been removed
> > since no userspace was using them. Otherwise they will become a
> > misleading for users, and users will fail with ENOTTY with wrong call.

> > -#define GIO_FONT	0x4B60	/* gets font in expanded form */
> > -#define PIO_FONT	0x4B61	/* use font in expanded form */
> > -#define GIO_FONTX	0x4B6B	/* get font using struct consolefontdesc */
> > -#define PIO_FONTX	0x4B6C	/* set font using struct consolefontdesc */
> > -struct consolefontdesc {
> > -#define PIO_FONTRESET   0x4B6D	/* reset to default font */

> Did you rebuild a distribution like Debian to verify that these values
> and structure are not used anywhere?

I just did.  https://codesearch.debian.net lists packages to check:
aalib
busybox
cde
console-cyrillic
dietlibc
doclifter
emscripten
fpc
gargoyle-free
gcc-10
gcc-11
gcc-12
gcc-9
gcc-arm-none-eabi
gcc-avr
gcc-riscv64-unknown-elf
gcc-snapshot
hurd
kbd
kfreebsd-10
lazarus
libabigail
libexplain
linux
llvm-toolchain-11
llvm-toolchain-12
llvm-toolchain-13
llvm-toolchain-14
llvm-toolchain-9
llvm-toolchain-snapshot
lynx
manpages-l10n
sequeler
strace
stress-ng
systemd
trinity
vala
valgrind

Of these, I've ignored the kernels, and built only the latest released
version of a compiler.

.--====[ aalib ]
aalinux.c: In function ‘linux_init’:
aalinux.c:106:34: error: storage size of ‘desc’ isn’t known
  106 |           struct consolefontdesc desc;
      |                                  ^~~~
aalinux.c:109:26: error: ‘GIO_FONTX’ undeclared (first use in this function)
  109 |           i = ioctl (fd, GIO_FONTX, &desc);
      |                          ^~~~~~~~~
`----

.--====[ kbd ]
kdfontop.c: In function ‘kfont_restore_font’:
kdfontop.c:27:23: error: ‘PIO_FONTRESET’ undeclared (first use in this function)
   27 |         if (ioctl(fd, PIO_FONTRESET, 0)) {
      |                       ^~~~~~~~~~~~~
kdfontop.c: In function ‘get_font_giofontx’:
kdfontop.c:89:32: error: storage size of ‘cfd’ isn’t known
kdfontop.c:102:30: error: ‘GIO_FONTX’ undeclared
kdfontop.c: In function ‘get_font_giofont’:
kdfontop.c:137:30: error: ‘GIO_FONT’ undeclared
kdfontop.c: In function ‘put_font_piofontx’:
kdfontop.c:242:32: error: storage size of ‘cfd’ isn’t known
kdfontop.c:262:31: error: ‘PIO_FONTX’ undeclared
kdfontop.c: In function ‘put_font_piofont’:
kdfontop.c:299:31: error: ‘PIO_FONT’ undeclared
`----

.--====[ gcc-12 ]
../../../../src/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cpp:850:29: error: 'GIO_FONT' was not declared in this scope
  850 |   unsigned IOCTL_GIO_FONT = GIO_FONT;
      |                             ^~~~~~~~
`----

.--====[ llvm-toolchain-14 ]
/<<PKGBUILDDIR>>/compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_posix.cpp:865:29: error: use of undeclared identifier 'GIO_FONT'
  unsigned IOCTL_GIO_FONT = GIO_FONT;
                            ^
/<<PKGBUILDDIR>>/compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_posix.cpp:898:29: error: use of undeclared identifier 'PIO_FONT'
  unsigned IOCTL_PIO_FONT = PIO_FONT;
                            ^
`----

.--====[ libexplain ]
libexplain/buffer/consolefontdesc.c: In function ‘explain_buffer_consolefontdesc’:
libexplain/buffer/consolefontdesc.c:34:48: error: invalid application of ‘sizeof’ to incomplete type ‘c
onst struct consolefontdesc’
   34 |     if (explain_is_efault_pointer(value, sizeof(*value)))
      |                                                ^
libexplain/buffer/consolefontdesc.c:43:14: error: invalid use of undefined type ‘const struct consolefo
ntdesc’
   43 |         value->charcount,
      |              ^~
`----

.--====[ trinity ]
In file included from ioctls/vt.c:8:
ioctls/vt.c:48:15: error: ‘GIO_FONT’ undeclared here (not in a function)
   48 |         IOCTL(GIO_FONT),
      |               ^~~~~~~~
include/ioctls.h:53:22: note: in definition of macro ‘IOCTL’
   53 |         { .request = _request, .name = #_request, }
      |                      ^~~~~~~~
ioctls/vt.c:49:15: error: ‘PIO_FONT’ undeclared here (not in a function)
   49 |         IOCTL(PIO_FONT),
      |               ^~~~~~~~
ioctls/vt.c:50:15: error: ‘GIO_FONTX’ undeclared here (not in a function)
ioctls/vt.c:51:15: error: ‘PIO_FONTX’ undeclared here (not in a function)
ioctls/vt.c:52:15: error: ‘PIO_FONTRESET’ undeclared here (not in a function)
`----


So there _are_ failures in userspace.
But let's take a look at them:

* aalib: dead upstream since 2001, this code is broken
* kbd: uses KDFONTOP, falls back if unsupported
* libsanitizer (bundled in gcc, llvm-toolchain): can drop
* libexplain: can drop
* trinity: can drop

So we have one real failure, one fallback, and a few "lists all ioctls".
I'd say that's acceptable.  Especially because presence of code that list
all ioctls means we would never done any clean-up otherwise.


Meow!
-- 
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⣾⠁⢠⠒⠀⣿⡁     Bactria → settled 2000-1000BC in northwest India.
⢿⡄⠘⠷⠚⠋⠀ Gypsies: came ~1000AD from northern India; aryan.
⠈⠳⣄⠀⠀⠀⠀ Germans: IE people who came ~2800BC to Scandinavia; not aryan.

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