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binfmt_misc: use print_hex_dump_debug() for the register debug output

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The hex dumps in create_entry() are compiled out unless someone edits
the file to define DEBUG while the pr_debug() calls right next to
them are dynamic-debug aware. Switch the dumps to
print_hex_dump_debug() which follows the same rules as pr_debug() so
the register parsing debug output is uniformly controlled through
dynamic debug, and remove the USE_DEBUG machinery.

Drop the magic[masked] dump instead of converting it: it printed the
bitwise AND of two buffers dumped right above it and required a
temporary allocation on every registration just to recompute what
the reader can derive from the magic and mask dumps directly.

Link: https://patch.msgid.link/20260710-work-binfmt_misc-locking-v3-11-a162f7cb58d6@kernel.org
Reviewed-by: Jori Koolstra <jkoolstra@xs4all.nl>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2026-07-10 11:33:12 +02:00
parent e496ea42ce
commit 18698b35b4
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
1 changed files with 15 additions and 37 deletions
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52
fs/binfmt_misc.c
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@ -32,12 +32,6 @@
#include "internal.h"
#ifdef DEBUG
# define USE_DEBUG 1
#else
# define USE_DEBUG 0
#endif
/* Entry status and match type bit numbers. */
enum binfmt_misc_entry_bits {
MISC_FMT_ENABLED_BIT = 0,
@ -459,10 +453,9 @@ static struct binfmt_misc_entry *create_entry(const char __user *buffer,
goto einval;
if (!e->magic[0])
goto einval;
if (USE_DEBUG)
print_hex_dump_bytes(
KBUILD_MODNAME ": register: magic[raw]: ",
DUMP_PREFIX_NONE, e->magic, p - e->magic);
print_hex_dump_debug(
KBUILD_MODNAME ": register: magic[raw]: ",
DUMP_PREFIX_NONE, 16, 1, e->magic, p - e->magic, true);
/* Parse the 'mask' field. */
e->mask = p;
@ -472,10 +465,12 @@ static struct binfmt_misc_entry *create_entry(const char __user *buffer,
if (!e->mask[0]) {
e->mask = NULL;
pr_debug("register: mask[raw]: none\n");
} else if (USE_DEBUG)
print_hex_dump_bytes(
} else {
print_hex_dump_debug(
KBUILD_MODNAME ": register: mask[raw]: ",
DUMP_PREFIX_NONE, e->mask, p - e->mask);
DUMP_PREFIX_NONE, 16, 1, e->mask, p - e->mask,
true);
}
/*
* Decode the magic & mask fields.
@ -491,30 +486,13 @@ static struct binfmt_misc_entry *create_entry(const char __user *buffer,
BINPRM_BUF_SIZE - e->size < e->offset)
goto einval;
pr_debug("register: magic/mask length: %i\n", e->size);
if (USE_DEBUG) {
print_hex_dump_bytes(
KBUILD_MODNAME ": register: magic[decoded]: ",
DUMP_PREFIX_NONE, e->magic, e->size);
if (e->mask) {
int i;
char *masked = kmalloc(e->size, GFP_KERNEL_ACCOUNT);
print_hex_dump_bytes(
KBUILD_MODNAME ": register: mask[decoded]: ",
DUMP_PREFIX_NONE, e->mask, e->size);
if (masked) {
for (i = 0; i < e->size; ++i)
masked[i] = e->magic[i] & e->mask[i];
print_hex_dump_bytes(
KBUILD_MODNAME ": register: magic[masked]: ",
DUMP_PREFIX_NONE, masked, e->size);
kfree(masked);
}
}
}
print_hex_dump_debug(
KBUILD_MODNAME ": register: magic[decoded]: ",
DUMP_PREFIX_NONE, 16, 1, e->magic, e->size, true);
if (e->mask)
print_hex_dump_debug(
KBUILD_MODNAME ": register: mask[decoded]: ",
DUMP_PREFIX_NONE, 16, 1, e->mask, e->size, true);
} else {
/* Handle the 'E' (extension) format. */