kmsan: don't use |pc| passed to __msan_poison_alloca()

It should be simpler to just get the necessary number of alloca stack
frames in __msan_poison_alloca().
Right now we store only the return address of __msan_poison_alloca() and
the caller, for which we need kmsan_internal_return_address().

mm/kmsan/kmsan.c

@@ -572,7 +572,7 @@ depot_stack_handle_t inline kmsan_internal_chain_origin(depot_stack_handle_t id,
 	if (full) {
 		entries[1] = kmsan_save_stack();
 	} else {
-		entries[1] = (unsigned long)__builtin_return_address(1);
+		entries[1] = (unsigned long)kmsan_internal_return_address(1);
 	}
 	entries[2] = id;
 	handle = depot_save_stack(&trace, GFP_ATOMIC);
@@ -905,32 +905,6 @@ void save_reporter(void *caller, void **table, int *index)
 	table[(*index)++] = caller;
 }
 
-// Dummy replacement for __builtin_return_address() which may crash without
-// frame pointers.
-inline void *return_address(int arg)
-{
-#ifdef CONFIG_UNWINDER_FRAME_POINTER
-	switch (arg) {
-		case 1:
-			return __builtin_return_address(1);
-		case 2:
-			return __builtin_return_address(2);
-		default:
-			BUG();
-	}
-#else
-	unsigned long entries[1];
-	struct stack_trace trace = {
-		.nr_entries = 0,
-		.entries = entries,
-		.max_entries = 1,
-		.skip = arg
-	};
-	save_stack_trace(&trace);
-	return entries[0];
-#endif
-}
-
 // |deep| is a dirty hack to skip an additional frame when calling
 // kmsan_report() from kmsan_copy_to_user().
 inline void kmsan_report(void *caller, depot_stack_handle_t origin,
@@ -970,13 +944,13 @@ inline void kmsan_report(void *caller, depot_stack_handle_t origin,
 	spin_lock_irqsave(&report_lock, flags);
 	save_reporter(caller, reporters_tbl, &reporters_index);
 	kmsan_pr_err("==================================================================\n");
-	// TODO(glider): inline this properly, avoid __builtin_return_address(1).
+	// TODO(glider): inline this properly
 	switch (reason) {
 		case REASON_ANY:
-			kmsan_pr_err("BUG: KMSAN: uninit-value in %pS\n", deep ? return_address(2) : return_address(1));
+			kmsan_pr_err("BUG: KMSAN: uninit-value in %pS\n", deep ? kmsan_internal_return_address(2) : kmsan_internal_return_address(1));
 			break;
 		case REASON_COPY_TO_USER:
-			kmsan_pr_err("BUG: KMSAN: kernel-infoleak in %pS\n", deep ? return_address(2) : return_address(1));
+			kmsan_pr_err("BUG: KMSAN: kernel-infoleak in %pS\n", deep ? kmsan_internal_return_address(2) : kmsan_internal_return_address(1));
 			break;
 	}
 	dump_stack();

mm/kmsan/kmsan.h

@@ -113,4 +113,31 @@ struct page *virt_to_page_or_null(const void *vaddr);
 void *get_cea_shadow_or_null(const void *addr);
 void *get_cea_origin_or_null(const void *addr);
 
+// Dummy replacement for __builtin_return_address() which may crash without
+// frame pointers.
+static inline void *kmsan_internal_return_address(int arg)
+{
+#ifdef CONFIG_UNWINDER_FRAME_POINTER
+	switch (arg) {
+		case 1:
+			return __builtin_return_address(1);
+		case 2:
+			return __builtin_return_address(2);
+		default:
+			BUG();
+	}
+#else
+	unsigned long entries[1];
+	struct stack_trace trace = {
+		.nr_entries = 0,
+		.entries = entries,
+		.max_entries = 1,
+		.skip = arg
+	};
+	save_stack_trace(&trace);
+	return entries[0];
+#endif
+}
+
+
 #endif

mm/kmsan/kmsan_instr.c

@@ -398,8 +398,7 @@ void *__msan_memcpy(void *dst, const void *src, u64 n)
 #if 0
 	if ((dst != src) && (!(((u64)dst + n <= (u64)src) || ((u64)src + n <= (u64)dst)))) {
 		kmsan_pr_err("==================================================================\n");
-		// TODO(glider): avoid __builtin_return_address(1).
-		kmsan_pr_err("WARNING: memcpy-param-overlap in %pS\n", __builtin_return_address(1));
+		kmsan_pr_err("WARNING: memcpy-param-overlap in %pS\n", kmsan_internal_return_address(1));
 		kmsan_pr_err("__msan_memcpy(%px, %px, %d)\n", dst, src, n);
 		dump_stack();
 		kmsan_pr_err("==================================================================\n");
@@ -558,7 +557,8 @@ inline void kmsan_set_origin_inline(u64 address, int size, u32 origin)
 }
 
 
-void __msan_poison_alloca(u64 address, u64 size, char *descr/*checked*/, u64 pc)
+// TODO(glider): drop the last argument.
+void __msan_poison_alloca(u64 address, u64 size, char *descr/*checked*/, u64 unused)
 {
 	depot_stack_handle_t handle;
 	BUG_ON(size > PAGE_SIZE * 4);
@@ -600,7 +600,7 @@ void __msan_poison_alloca(u64 address, u64 size, char *descr/*checked*/, u64 pc)
 	entries[0] = KMSAN_ALLOCA_MAGIC_ORIGIN;
 	entries[1] = (u64)descr;
 	entries[2] = __builtin_return_address(0);
-	entries[3] = pc;
+	entries[3] = kmsan_internal_return_address(1);
 
 	ENTER_RUNTIME(irq_flags);
 	handle = depot_save_stack(&trace, GFP_ATOMIC);