diff options
| author | Song Liu <song@kernel.org> | 2022-02-04 10:57:38 -0800 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2022-02-07 18:13:01 -0800 |
| commit | 0e06b40371682b6b70ed0302a7baec0698ada95c (patch) | |
| tree | 1454520f94a7d83492bc05abda857a7a01a36550 /arch/x86 | |
| parent | d00c6473b1ee9050cc36d008c6d30bf0d3de0524 (diff) | |
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: 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
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/include/asm/text-patching.h | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/alternative.c | 34 |
2 files changed, 35 insertions, 0 deletions
diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h index b7421780e4e9..4cc18ba1b75e 100644 --- a/arch/x86/include/asm/text-patching.h +++ b/arch/x86/include/asm/text-patching.h @@ -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); diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 5007c3ffe96f..018b61febf0e 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -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(); |