Commit 0e06b403 authored by Song Liu's avatar Song Liu Committed by Alexei Starovoitov
Browse files

x86/alternative: Introduce text_poke_copy 



This will be used by BPF jit compiler to dump JITed binary to a RX huge
page, and thus allow multiple BPF programs sharing the a huge (2MB) page.

Signed-off-by: default avatarSong Liu <song@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/bpf/20220204185742.271030-6-song@kernel.org
parent d00c6473

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

+1 −0
Original line number Diff line number Diff line
@@ -44,6 +44,7 @@ extern void text_poke_early(void *addr, const void *opcode, size_t len); 
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 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

+34 −0
Original line number Diff line number Diff line
@@ -1102,6 +1102,40 @@ void *text_poke_kgdb(void *addr, const void *opcode, size_t len) 
	return __text_poke(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)

{

	unsigned long start = (unsigned long)addr;

	size_t patched = 0;



	if (WARN_ON_ONCE(core_kernel_text(start)))

		return NULL;



	mutex_lock(&text_mutex);

	while (patched < len) {

		unsigned long ptr = start + patched;

		size_t s;



		s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched);



		__text_poke((void *)ptr, opcode + patched, s);

		patched += s;

	}

	mutex_unlock(&text_mutex);

	return addr;

}



static void do_sync_core(void *info)

{

	sync_core();