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Subject[PATCH v2 bpf-next 5/7] x86/alternative: introduce text_poke_jit
Date
This will be used by BPF jit compiler to dump JITed binary to a RWX huge
page, and thus allow multiple BPF programs sharing the a huge (2MB) page.

Signed-off-by: Song Liu <song@kernel.org>
---
arch/x86/include/asm/text-patching.h | 1 +
arch/x86/kernel/alternative.c | 28 ++++++++++++++++++++++++++++
2 files changed, 29 insertions(+)

diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h
index b7421780e4e9..991058c9b4b1 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_jit(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 23fb4d51a5da..02c35725cc62 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -1102,6 +1102,34 @@ void *text_poke_kgdb(void *addr, const void *opcode, size_t len)
return __text_poke(addr, opcode, len);
}

+/**
+ * text_poke_jit - Update instructions on a live kernel by jit engine
+ * @addr: address to modify
+ * @opcode: source of the copy
+ * @len: length to copy, could be more than 2x PAGE_SIZE
+ *
+ * Only module memory taking jit text (e.g. for bpf) should be patched.
+ */
+void *text_poke_jit(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;
+
+ 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;
+ }
+ return addr;
+}
+
static void do_sync_core(void *info)
{
sync_core();
--
2.30.2
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