KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 122 insertions, 0 deletions

diff --git a/tools/objtool/objtool.c b/tools/objtool/objtool.c
new file mode 100644
index 000000000..a4e139dee
--- /dev/null
+++ b/tools/objtool/objtool.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
+ */
+
+#include <stdio.h>
+#include <stdbool.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <subcmd/exec-cmd.h>
+#include <subcmd/pager.h>
+#include <linux/kernel.h>
+
+#include <objtool/builtin.h>
+#include <objtool/objtool.h>
+#include <objtool/warn.h>
+
+static struct objtool_file file;
+
+struct objtool_file *objtool_open_read(const char *filename)
+{
+	if (file.elf) {
+		ERROR("won't handle more than one file at a time");
+		return NULL;
+	}
+
+	file.elf = elf_open_read(filename, O_RDWR);
+	if (!file.elf)
+		return NULL;
+
+	hash_init(file.insn_hash);
+	INIT_LIST_HEAD(&file.retpoline_call_list);
+	INIT_LIST_HEAD(&file.return_thunk_list);
+	INIT_LIST_HEAD(&file.static_call_list);
+	INIT_LIST_HEAD(&file.mcount_loc_list);
+	INIT_LIST_HEAD(&file.endbr_list);
+	INIT_LIST_HEAD(&file.call_list);
+	file.ignore_unreachables = opts.no_unreachable;
+	file.hints = false;
+
+	return &file;
+}
+
+int objtool_pv_add(struct objtool_file *f, int idx, struct symbol *func)
+{
+	if (!opts.noinstr)
+		return 0;
+
+	if (!f->pv_ops) {
+		ERROR("paravirt confusion");
+		return -1;
+	}
+
+	/*
+	 * These functions will be patched into native code,
+	 * see paravirt_patch().
+	 */
+	if (!strcmp(func->name, "_paravirt_nop") ||
+	    !strcmp(func->name, "_paravirt_ident_64"))
+		return 0;
+
+	/* already added this function */
+	if (!list_empty(&func->pv_target))
+		return 0;
+
+	list_add(&func->pv_target, &f->pv_ops[idx].targets);
+	f->pv_ops[idx].clean = false;
+	return 0;
+}
+
+char *top_level_dir(const char *file)
+{
+	ssize_t len, self_len, file_len;
+	char self[PATH_MAX], *str;
+	int i;
+
+	len = readlink("/proc/self/exe", self, sizeof(self) - 1);
+	if (len <= 0)
+		return NULL;
+	self[len] = '\0';
+
+	for (i = 0; i < 3; i++) {
+		char *s = strrchr(self, '/');
+		if (!s)
+			return NULL;
+		*s = '\0';
+	}
+
+	self_len = strlen(self);
+	file_len = strlen(file);
+
+	str = malloc(self_len + file_len + 2);
+	if (!str)
+		return NULL;
+
+	memcpy(str, self, self_len);
+	str[self_len] = '/';
+	strcpy(str + self_len + 1, file);
+
+	return str;
+}
+
+int main(int argc, const char **argv)
+{
+	static const char *UNUSED = "OBJTOOL_NOT_IMPLEMENTED";
+
+	if (init_signal_handler())
+		return -1;
+
+	/* libsubcmd init */
+	exec_cmd_init("objtool", UNUSED, UNUSED, UNUSED);
+	pager_init(UNUSED);
+
+	if (argc > 1 && !strcmp(argv[1], "klp")) {
+		argc--;
+		argv++;
+		return cmd_klp(argc, argv);
+	}
+
+	return objtool_run(argc, argv);
+}