WIP: (squash) klp-convert: test multiple sections

Note: squash with ("livepatch/selftests: add klp-convert")

Add a test case in which klp-convert needs to convert a symbol that is shared
across ELF sections.  Special sections like .altinstructions do this.
It is possible that symbols may be shared across various .text sections
as well.

Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>

lib/livepatch/Makefile

@@ -9,6 +9,7 @@ obj-$(CONFIG_TEST_LIVEPATCH) += test_klp_atomic_replace.o \
 				test_klp_callbacks_mod.o \
 				test_klp_convert1.o \
 				test_klp_convert2.o \
+				test_klp_convert_sections.o \
 				test_klp_convert_mod.o \
 				test_klp_livepatch.o \
 				test_klp_shadow_vars.o \

lib/livepatch/test_klp_convert_sections.c

@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2020 Joe Lawrence <joe.lawrence@redhat.com>
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/livepatch.h>
+#include "test_klp_convert.h"
+
+/* klp-convert symbols - vmlinux */
+extern char *saved_command_line;
+
+/*
+ * Scatter references to the same symbol (saved_command_line) across a
+ * few different ELF sections.  At the same time, include multiple
+ * references within the same function.
+ */
+__section(".text.print_saved_command_line")
+void print_saved_command_line(void)
+{
+	pr_info("saved_command_line (1): %s\n", saved_command_line);
+}
+
+__section(".text.print_saved_command_line2")
+void print_saved_command_line2(void)
+{
+	pr_info("saved_command_line (1): %s\n", saved_command_line);
+	pr_info("saved_command_line (2): %s\n", saved_command_line);
+}
+
+__section(".text.print_saved_command_line3")
+void print_saved_command_line3(void)
+{
+	pr_info("saved_command_line (1): %s\n", saved_command_line);
+	pr_info("saved_command_line (2): %s\n", saved_command_line);
+	pr_info("saved_command_line (3): %s\n", saved_command_line);
+}
+
+/*
+ * Create relocations in .rela.data that need conversion, sharing
+ * symbols with ordinary .text relas.
+ */
+const char *(*p_test_klp_get_driver_name)(void) = test_klp_get_driver_name;
+const char *(*p_get_homonym_string)(void) = get_homonym_string;
+
+void print_via_function_pointers(void)
+{
+	pr_info("test_klp_get_driver_name(): %s\n", test_klp_get_driver_name());
+	pr_info("p_test_klp_get_driver_name(): %s\n", p_test_klp_get_driver_name());
+	pr_info("get_homonym_string(): %s\n", get_homonym_string());
+	pr_info("p_get_homonym_string(): %s\n", p_get_homonym_string());
+}
+
+/* provide a sysfs handle to invoke debug functions */
+static int print_debug;
+static int print_debug_set(const char *val, const struct kernel_param *kp)
+{
+	print_saved_command_line();
+	print_saved_command_line2();
+	print_saved_command_line3();
+	print_via_function_pointers();
+
+	return 0;
+}
+static const struct kernel_param_ops print_debug_ops = {
+	.set = print_debug_set,
+	.get = param_get_int,
+};
+
+module_param_cb(print_debug, &print_debug_ops, &print_debug, 0200);
+MODULE_PARM_DESC(print_debug, "print klp-convert debugging info");
+
+
+KLP_MODULE_RELOC(test_klp_convert_mod) test_klp_convert_mod_relocs_a[] = {
+	KLP_SYMPOS(get_homonym_string, 1),
+};
+
+static struct klp_func funcs[] = {
+	{
+	}, { }
+};
+
+static struct klp_object objs[] = {
+	{
+		/* name being NULL means vmlinux */
+		.funcs = funcs,
+	},
+	{
+		.name = "test_klp_convert_mod",
+		.funcs = funcs,
+	}, { }
+};
+
+static struct klp_patch patch = {
+	.mod = THIS_MODULE,
+	.objs = objs,
+};
+
+static int test_klp_convert_sections_init(void)
+{
+	int ret;
+
+	ret = klp_enable_patch(&patch);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static void test_klp_convert_sections_exit(void)
+{
+}
+
+module_init(test_klp_convert_sections_init);
+module_exit(test_klp_convert_sections_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Joe Lawrence <joe.lawrence@redhat.com>");
+MODULE_DESCRIPTION("Livepatch test: klp-convert-sections");
+MODULE_INFO(livepatch, "Y");

tools/testing/selftests/livepatch/test-livepatch.sh

@@ -297,4 +297,47 @@ livepatch: '$MOD_KLP_CONVERT2': unpatching complete
 % rmmod $MOD_KLP_CONVERT2
 % rmmod $MOD_KLP_CONVERT_MOD"
 
+
+# TEST: klp-convert symbols across ELF sections
+# - load a livepatch that references symbols that require klp-convert
+#   and reference the same symbol from multiple ELF sections
+# - verify correct behavior
+# - unload the livepatch
+
+start_test "klp-convert symbols across ELF sections"
+
+saved_cmdline=$(cat /proc/cmdline)
+
+load_mod $MOD_KLP_CONVERT_MOD
+load_lp $MOD_KLP_CONVERT_SECTIONS
+echo 1 > /sys/module/$MOD_KLP_CONVERT_SECTIONS/parameters/print_debug
+disable_lp $MOD_KLP_CONVERT_SECTIONS
+unload_lp $MOD_KLP_CONVERT_SECTIONS
+unload_mod $MOD_KLP_CONVERT_MOD
+
+check_result "% modprobe $MOD_KLP_CONVERT_MOD
+% modprobe $MOD_KLP_CONVERT_SECTIONS
+livepatch: enabling patch '$MOD_KLP_CONVERT_SECTIONS'
+livepatch: '$MOD_KLP_CONVERT_SECTIONS': initializing patching transition
+livepatch: '$MOD_KLP_CONVERT_SECTIONS': starting patching transition
+livepatch: '$MOD_KLP_CONVERT_SECTIONS': completing patching transition
+livepatch: '$MOD_KLP_CONVERT_SECTIONS': patching complete
+$MOD_KLP_CONVERT_SECTIONS: saved_command_line (1): $saved_cmdline
+$MOD_KLP_CONVERT_SECTIONS: saved_command_line (1): $saved_cmdline
+$MOD_KLP_CONVERT_SECTIONS: saved_command_line (2): $saved_cmdline
+$MOD_KLP_CONVERT_SECTIONS: saved_command_line (1): $saved_cmdline
+$MOD_KLP_CONVERT_SECTIONS: saved_command_line (2): $saved_cmdline
+$MOD_KLP_CONVERT_SECTIONS: saved_command_line (3): $saved_cmdline
+$MOD_KLP_CONVERT_SECTIONS: test_klp_get_driver_name(): $MOD_KLP_CONVERT_MOD
+$MOD_KLP_CONVERT_SECTIONS: p_test_klp_get_driver_name(): $MOD_KLP_CONVERT_MOD
+$MOD_KLP_CONVERT_SECTIONS: get_homonym_string(): homonym string A
+$MOD_KLP_CONVERT_SECTIONS: p_get_homonym_string(): homonym string A
+% echo 0 > /sys/kernel/livepatch/$MOD_KLP_CONVERT_SECTIONS/enabled
+livepatch: '$MOD_KLP_CONVERT_SECTIONS': initializing unpatching transition
+livepatch: '$MOD_KLP_CONVERT_SECTIONS': starting unpatching transition
+livepatch: '$MOD_KLP_CONVERT_SECTIONS': completing unpatching transition
+livepatch: '$MOD_KLP_CONVERT_SECTIONS': unpatching complete
+% rmmod $MOD_KLP_CONVERT_SECTIONS
+% rmmod $MOD_KLP_CONVERT_MOD"
+
 exit 0