diff mbox series

[v5,bpf-next,5/7] x86/alternative: introduce text_poke_copy

Message ID 20220120191306.1801459-6-song@kernel.org (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series bpf_prog_pack allocator | expand

Checks

Context Check Description
bpf/vmtest-bpf-next-PR fail PR summary
netdev/tree_selection success Clearly marked for bpf-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 7288 this patch: 7288
netdev/cc_maintainers warning 11 maintainers not CCed: hpa@zytor.com jpoimboe@redhat.com bp@alien8.de kpsingh@kernel.org john.fastabend@gmail.com kafai@fb.com songliubraving@fb.com dave.hansen@linux.intel.com yhs@fb.com mingo@redhat.com tglx@linutronix.de
netdev/build_clang success Errors and warnings before: 719 this patch: 719
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 6651 this patch: 6651
netdev/checkpatch warning CHECK: extern prototypes should be avoided in .h files WARNING: line length of 86 exceeds 80 columns
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next fail VM_Test

Commit Message

Song Liu Jan. 20, 2022, 7:13 p.m. UTC 
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>
---
 arch/x86/include/asm/text-patching.h |  1 +
 arch/x86/kernel/alternative.c        | 32 ++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

Comments

Peter Zijlstra Jan. 21, 2022, 9:52 a.m. UTC | #1 
On Thu, Jan 20, 2022 at 11:13:03AM -0800, Song Liu wrote:
> 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>

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
diff mbox series

Patch

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 23fb4d51a5da..903a415c19fa 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -1102,6 +1102,38 @@  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;
+
+	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();