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x86/alternative: Introduce text_poke_copy

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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: Song Liu <song@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/bpf/20220204185742.271030-6-song@kernel.org
This commit is contained in:
Song Liu 2022-02-04 10:57:38 -08:00 committed by Alexei Starovoitov
parent d00c6473b1
commit 0e06b40371
2 changed files with 35 additions and 0 deletions
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1
arch/x86/include/asm/text-patching.h
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@ -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);

34
arch/x86/kernel/alternative.c
View File

@ -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();