Commit fe54d079 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Peter Zijlstra
Browse files

x86/alternatives: Provide text_poke_copy_locked() 



The upcoming call thunk patching must hold text_mutex and needs access to
text_poke_copy(), which takes text_mutex.

Provide a _locked postfixed variant to expose the inner workings.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220915111147.159977224@infradead.org
parent 80e4c1cd

arch/x86/include/asm/text-patching.h

+1 −0
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ extern void *text_poke(void *addr, const void *opcode, size_t len); 
extern void text_poke_sync(void);

extern void *text_poke_kgdb(void *addr, const void *opcode, size_t len);

extern void *text_poke_copy(void *addr, const void *opcode, size_t len);

extern void *text_poke_copy_locked(void *addr, const void *opcode, size_t len, bool core_ok);

extern void *text_poke_set(void *addr, int c, size_t len);

extern int poke_int3_handler(struct pt_regs *regs);

extern void text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate);

arch/x86/kernel/alternative.c

+22 −15
Original line number Diff line number Diff line
@@ -1236,27 +1236,15 @@ void *text_poke_kgdb(void *addr, const void *opcode, size_t len) 
	return __text_poke(text_poke_memcpy, addr, opcode, len);

}



/**

 * text_poke_copy - Copy instructions into (an unused part of) RX memory

 * @addr: address to modify

 * @opcode: source of the copy

 * @len: length to copy, could be more than 2x PAGE_SIZE

 *

 * Not safe against concurrent execution; useful for JITs to dump

 * new code blocks into unused regions of RX memory. Can be used in

 * conjunction with synchronize_rcu_tasks() to wait for existing

 * execution to quiesce after having made sure no existing functions

 * pointers are live.

 */

void *text_poke_copy(void *addr, const void *opcode, size_t len)

void *text_poke_copy_locked(void *addr, const void *opcode, size_t len,

			    bool core_ok)

{

	unsigned long start = (unsigned long)addr;

	size_t patched = 0;



	if (WARN_ON_ONCE(core_kernel_text(start)))

	if (WARN_ON_ONCE(!core_ok && core_kernel_text(start)))

		return NULL;



	mutex_lock(&text_mutex);

	while (patched < len) {

		unsigned long ptr = start + patched;

		size_t s;
@@ -1266,6 +1254,25 @@ void *text_poke_copy(void *addr, const void *opcode, size_t len) 
		__text_poke(text_poke_memcpy, (void *)ptr, opcode + patched, s);

		patched += s;

	}

	return addr;

}



/**

 * text_poke_copy - Copy instructions into (an unused part of) RX memory

 * @addr: address to modify

 * @opcode: source of the copy

 * @len: length to copy, could be more than 2x PAGE_SIZE

 *

 * Not safe against concurrent execution; useful for JITs to dump

 * new code blocks into unused regions of RX memory. Can be used in

 * conjunction with synchronize_rcu_tasks() to wait for existing

 * execution to quiesce after having made sure no existing functions

 * pointers are live.

 */

void *text_poke_copy(void *addr, const void *opcode, size_t len)

{

	mutex_lock(&text_mutex);

	addr = text_poke_copy_locked(addr, opcode, len, false);

	mutex_unlock(&text_mutex);

	return addr;

}