print_hex_dump(9)

✨ print_hex_dump(9) ✨

okay so bestie, we're reading the kernel API manual rn — this one's print_hex_dump from the Kernel API Manual, and honestly? it's giving "hex dump but make it fashion" 💅

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🌸 NAME 🌸

print_hex_dump — prints a text hex dump to syslog for a binary blob of data 📝✨ lowkey iconic behaviour, fr fr.

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🎀 SYNOPSIS 🎀

void print_hex_dump (const char *level , const char *prefix_str , int
prefix_type , int rowsize , int groupsize , const void *buf , size_t len
, bool ascii );

like, that's the whole vibe right there 👑 one function, eight arguments, zero chill.

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🦋 ARGUMENTS 🦋

so there are EIGHT of these bad boys and you gotta get them all right, no cap. let's go one by one 🫶

• level — the kernel log level, like KERN_DEBUG. basically how loud you want this dump to be screaming into the logs 🔊
• prefix_str — the string you want slapped in front of every single line. the caller supplies the trailing spaces for alignment if they want it all nice and lined up — that's on you, not on the function, periodt ✨
• prefix_type — controls whether you get a prefix of an offset, an address, or literally nothing at all. your options are DUMP_PREFIX_OFFSET, DUMP_PREFIX_ADDRESS, DUMP_PREFIX_NONE 🎯
• rowsize — how many bytes you print per line. must be 16 or 32 — no other numbers, bestie, I don't make the rules 😤
• groupsize — how many bytes you print at a time (1, 2, 4, 8; default = 1) 🍓
• buf — the data blob you're dumping. this is the main character, the actual content, the whole reason we're here 💖
• len — the number of bytes in buf. gotta tell it how much to look at, or it's just guessing 🙈
• ascii — include ASCII after the hex output. set this and you get the cute little readable column on the side 🌈

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💜 DESCRIPTION 💜

Given a buffer of u8 data, print_hex_dump prints a hex + ASCII dump to the kernel log at the specified kernel log level, with an optional leading prefix. simple as that, slay 💅

print_hex_dump works on one "line" of output at a time — i.e., 16 or 32 bytes of input data converted to hex + ASCII output. then print_hex_dump iterates over the entire input buf, breaking it into "line size" chunks to format and print. one line at a time, over and over, till it's done — it's giving main character energy with a very repetitive routine 🌀

E.g.:

print_hex_dump(KERN_DEBUG, "raw data: ", DUMP_PREFIX_ADDRESS, 16, 1, frame->data, frame->len, true);

Example output using DUMP_PREFIX_OFFSET and 1-byte mode:

0009ab42: 40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f  ABCDEFGHIJKLMNO

Example output using DUMP_PREFIX_ADDRESS and 4-byte mode:

ffffffff88089af0: 73727170 77767574 7b7a7978 7f7e7d7c  pqrstuvwxyz{|}~.

like... look at that formatting. the alignment. the little ASCII column just vibing on the right. obsessed 😭✨

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🧚 SEE ALSO 🧚

• Kernel file ./lib/hexdump.c
• hex_to_bin(9)
• hex2bin(9)
• bin2hex(9)
• hex_dump_to_buffer(9)

go read those next, iykyk 🦋

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and that's the whole page bestie 🫶 this one lives in ./lib and the date on it is October 2026 — so yeah, print it out and put it on your wall, it's a keeper 💖🎀💅