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// SPDX-License-Identifier: GPL-2.0
/*
* Static branch in a patched function. The jump table entry is written out by
* hand, mirroring JUMP_TABLE_ENTRY(), so the fixture builds without kernel
* headers. The key is an STT_OBJECT; anything else is ignored by
* validate_special_section_klp_reloc().
*
* MODNAME selects whether the key is taken to belong to vmlinux or a module.
*
* NEW_KEY puts the whole static branch behind PATCHED, so the patch introduces
* one where the original had none -- a different question from patching code
* that already has a key, because the __jump_table entry itself is new.
*
* KEY_NAME renames the key. Two names are special to
* validate_special_section_klp_reloc(): a __tracepoint_* key and the
* __UNIQUE_ID_ddebug_* one pr_debug() generates are both unsupported in a
* module, but are disabled with a warning rather than rejected, because the
* kernel is full of them and refusing outright would make ordinary functions
* unpatchable.
*
* STATIC_KEY makes the key file-local. That changes the shape of the
* relocation rather than the meaning of the code: a reference to a static lands
* on the section symbol plus an addend, so the key has to be resolved from the
* section before it can be recognised as a key at all.
*/
#ifndef MODNAME
#define MODNAME "vmlinux"
#endif
#ifndef KEY_NAME
#define KEY_NAME klp_test_key
#endif
static const char __modinfo[]
__attribute__((section(".modinfo"), used, aligned(1))) = "\0name=" MODNAME;
#ifdef STATIC_KEY
static long KEY_NAME;
#else
long KEY_NAME;
#endif
int target(int x)
{
int r = x;
#if defined(NEW_KEY) && !defined(PATCHED)
/* The original has no static branch at all. */
return r + 1;
#else
asm goto(
"1: nop\n\t"
".pushsection __jump_table, \"aw\"\n\t"
".balign 8\n\t"
"912:\n\t"
".pushsection .discard.annotate_data, \"M\", @progbits, 8\n\t"
".long 912b - ., 1\n\t"
".popsection\n\t"
".long 1b - ., %l[l_yes] - .\n\t"
".quad %c0 - .\n\t"
".popsection\n\t"
: : "i" (&KEY_NAME) : : l_yes);
r += 1;
goto out;
l_yes:
r += 2;
out:
#endif
#ifdef PATCHED
return r + 100;
#else
return r;
#endif
}
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