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lib/fonts: Create font_data_t from struct console_font with font_data_import()

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Add font_data_import() and update consoles to use it.

The implementation of font_data_import() is based on code from fbcon,
which supports overflow checks and crc32 checksums. Fbcon uses the crc32
checksum.

Newport_con now implements the same overflow checks as fbcon. As before,
this console does not support checksums, which are optional. Newport_con
can now also handle input font data with a vertical pitch other than 32
bytes. (The vertical pitch is the offset between two glyphs in the font
data.)

As an internal change, remove the const qualifier from the data field
if struct font_data. This allows font_data_import() to write the data
without type casting. For all users of the font data via font_data_t,
the stored data is still read only.

v3:
- fix typos

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Helge Deller <deller@gmx.de>
This commit is contained in:
Thomas Zimmermann
2026-03-09 15:14:53 +01:00
committed by Helge Deller
parent 1e3c49aa03
commit 514d0de7cf
4 changed files with 75 additions and 53 deletions
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62
lib/fonts/fonts.c
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@@ -14,7 +14,9 @@
#include <linux/container_of.h>
#include <linux/font.h>
#include <linux/kd.h>
#include <linux/module.h>
#include <linux/overflow.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/types.h>
@@ -23,6 +25,8 @@
#include <asm/setup.h>
#endif
#define console_font_pitch(font) DIV_ROUND_UP((font)->width, 8)
/*
* Helpers for font_data_t
*/
@@ -42,6 +46,64 @@ static void font_data_free(font_data_t *fd)
kfree(to_font_data_struct(fd));
}
/**
* font_data_import - Allocates and initializes font data from user space
* @font: A font from user space
* @vpitch: The size of a single glyph in @font in bytes
* @calc_csum: An optional helper to calculate a chechsum
*
* Font data from user space must be translated to the kernel's format. The
* font's glyph geometry and data is provided in @font. The parameter @vpitch
* gives the number of bytes per glyph, including trailing bytes.
*
* The parameter @calc_csum is optional. Fbcon passes crc32() to calculate the
* font data's checksum.
*
* Returns:
* Newly initialized font data on success, or a pointer-encoded errno value otherwise.
*/
font_data_t *font_data_import(const struct console_font *font, unsigned int vpitch,
u32 (*calc_csum)(u32, const void *, size_t))
{
unsigned int pitch = console_font_pitch(font);
unsigned int h = font->height;
unsigned int charcount = font->charcount;
const unsigned char *data = font->data;
u32 csum = 0;
struct font_data *font_data;
int size, alloc_size;
unsigned int i;
font_data_t *fd;
/* Check for integer overflow in font-size calculation */
if (check_mul_overflow(h, pitch, &size) ||
check_mul_overflow(size, charcount, &size))
return ERR_PTR(-EINVAL);
/* Check for overflow in allocation size calculation */
if (check_add_overflow(sizeof(*font_data), size, &alloc_size))
return ERR_PTR(-EINVAL);
font_data = kmalloc(alloc_size, GFP_USER);
if (!font_data)
return ERR_PTR(-ENOMEM);
memset(font_data->extra, 0, sizeof(font_data->extra));
for (i = 0; i < charcount; ++i)
memcpy(font_data->data + i * h * pitch, data + i * vpitch * pitch, h * pitch);
if (calc_csum)
csum = calc_csum(0, font_data->data, size);
fd = font_data->data;
REFCOUNT(fd) = 1; /* start with reference acquired */
FNTSIZE(fd) = size;
FNTSUM(fd) = csum;
return fd;
}
EXPORT_SYMBOL_GPL(font_data_import);
/**
* font_data_get - Acquires a reference on font data
* @fd: Font data