[PATCH v6][makedumpfile 06/10] Add makedumpfile extensions support

The extensions can be specified by makedumpfile cmdline parameter as
"--extension", followed by extension's filename or absolute path. If
filename is give, then "./", "./extenisons" and
"/usr/lib64/makedumpfile/extensions/" will be searched.

The procedures of extensions are as follows:

Step 0: Every extensions will declare which kernel symbol/types they needed
during programming. This info will be stored within .init_ksyms/ktypes section.
Also extension will have a callback function for makedumpfile to call.

Step 1: Register .init_ksyms and .init_ktypes sections of makedumpfile
itself and extension's .so files, then tell kallsyms/btf subcomponent that which
kernel symbols/types will be resolved. And callbacks are also registered.

Step 2: Init kernel/module's btf/kallsyms on demand. Any un-needed kenrel
modules will be skipped.

Step 3: During btf/kallsyms parsing, the needed info will be filled. For
syms/types which are defined via INIT_MOD_OPT(...) macro, these are optinal
syms/types, it won't fail at parsing step if any are missing, instead, they
need to be checked within extension_init() of each extensions; Otherwise for
syms/types which defined via INIT_MOD(...) macro, these are must-have syms/types,
if any missing, the extension will fail at this step and as a result
this extension will be skipped.

After this step, required kernel symbol value and kernel types size/offset
are resolved, the extensions are ready to go.

Step 4: When makedumpfile doing page filtering, in addition to its
original filtering mechanism, it will call extensions callbacks for advices
whether the page should be included/excluded.

Reviewed-by: Stephen Brennan <[email protected]>
Signed-off-by: Tao Liu <[email protected]>
---
 Makefile            |  13 +-
 extension.c         | 355 ++++++++++++++++++++++++++++++++++++++++++++
 extension.h         |  16 ++
 extensions/Makefile |  11 ++
 makedumpfile.c      |  41 ++++-
 makedumpfile.h      |   1 +
 6 files changed, 430 insertions(+), 7 deletions(-)
 create mode 100644 extension.c
 create mode 100644 extension.h
 create mode 100644 extensions/Makefile

diff --git a/Makefile b/Makefile
index 1c51802..7e37f13 100644
--- a/Makefile
+++ b/Makefile
@@ -45,7 +45,7 @@ CFLAGS_ARCH += -m32
 endif
 
 SRC_BASE = makedumpfile.c makedumpfile.h diskdump_mod.h sadump_mod.h sadump_info.h
-SRC_PART = print_info.c dwarf_info.c elf_info.c erase_info.c sadump_info.c cache.c tools.c printk.c detect_cycle.c kallsyms.c btf_info.c
+SRC_PART = print_info.c dwarf_info.c elf_info.c erase_info.c sadump_info.c cache.c tools.c printk.c detect_cycle.c kallsyms.c btf_info.c extension.c
 OBJ_PART=$(patsubst %.c,%.o,$(SRC_PART))
 SRC_ARCH = arch/arm.c arch/arm64.c arch/x86.c arch/x86_64.c arch/ia64.c arch/ppc64.c arch/s390x.c arch/ppc.c arch/sparc64.c arch/mips64.c arch/loongarch64.c arch/riscv64.c
 OBJ_ARCH=$(patsubst %.c,%.o,$(SRC_ARCH))
@@ -73,6 +73,11 @@ LIBS := -lzstd $(LIBS)
 CFLAGS += -DUSEZSTD
 endif
 
+ifeq ($(EXTENSION), on)
+LIBS := -lbpf $(LIBS)
+CFLAGS += -DEXTENSION
+endif
+
 ifeq ($(DEBUG), on)
 # Requires libasan
 CFLAGS += -fsanitize=address
@@ -126,6 +131,7 @@ eppic_makedumpfile.so: extension_eppic.c
 
 clean:
 	rm -f $(OBJ) $(OBJ_PART) $(OBJ_ARCH) makedumpfile makedumpfile.8 makedumpfile.conf.5
+	$(MAKE) -C extensions clean
 
 install:
 	install -m 755 -d ${DESTDIR}/${SBINDIR} ${DESTDIR}/usr/share/man/man5 ${DESTDIR}/usr/share/man/man8
@@ -135,3 +141,8 @@ install:
 	mkdir -p ${DESTDIR}/usr/share/makedumpfile/eppic_scripts
 	install -m 644 -D $(VPATH)makedumpfile.conf ${DESTDIR}/usr/share/makedumpfile/makedumpfile.conf.sample
 	install -m 644 -t ${DESTDIR}/usr/share/makedumpfile/eppic_scripts/ $(VPATH)eppic_scripts/*
+
+.PHONY: extensions
+extensions:
+	$(MAKE) -C extensions CC=$(CC)
+
diff --git a/extension.c b/extension.c
new file mode 100644
index 0000000..3cea0e9
--- /dev/null
+++ b/extension.c
@@ -0,0 +1,355 @@
+#include <stdio.h>
+#include "extension.h"
+#include "makedumpfile.h"
+#ifdef EXTENSION
+#include <string.h>
+#include <dirent.h>
+#include <dlfcn.h>
+#include <stdbool.h>
+#include <unistd.h>
+#include "kallsyms.h"
+#include "btf_info.h"
+
+typedef int (*callback_fn)(unsigned long, const void *);
+
+struct extension_handle_cb {
+	void *handle;
+	callback_fn cb;
+};
+
+/* Extension .so extension_handle_cb array */
+static struct extension_handle_cb **handle_cbs = NULL;
+static int handle_cbs_len = 0;
+static int handle_cbs_cap = 0;
+
+/* Extension option array */
+static char **extension_opts = NULL;
+static int extension_opts_len = 0;
+static int extension_opts_cap = 0;
+
+static const char *dirs[] = {
+	"./",
+	"./extensions/",
+	"/usr/lib64/makedumpfile/extensions/",
+};
+
+bool add_extension_opts(char *opt)
+{
+	if (!add_to_arr((void ***)&extension_opts, &extension_opts_len,
+			&extension_opts_cap, opt)) {
+		/*
+		 * If fail, print error info and skip the extension.
+		*/
+		ERRMSG("Fail to add extension %s\n", opt);
+		return false;
+	} else {
+		return true;
+	}
+}
+
+static bool init_kallsyms_btf(void)
+{
+	int count;
+	bool ret = false;
+	/* We will load module's btf/kallsyms on demand */
+	bool init_ksyms_module = false;
+	bool init_ktypes_module = false;
+
+	if (check_ksyms_require_modname("vmlinux", &count)) {
+		if (!init_kernel_kallsyms())
+			goto out;
+		if (count >= 2)
+			init_ksyms_module = true;
+	}
+	if (check_ktypes_require_modname("vmlinux", &count)) {
+		if (!init_kernel_btf())
+			goto out;
+		if (count >= 2)
+			init_ktypes_module = true;
+	}
+	if (init_ksyms_module && !init_module_kallsyms())
+		goto out;
+	if (init_ktypes_module && !init_module_btf())
+		goto out;	
+	ret = true;
+out:
+	return ret;
+}
+
+static void cleanup_kallsyms_btf(void)
+{
+	cleanup_kallsyms();
+	cleanup_btf();
+}
+
+static void load_extensions(void)
+{
+	char path[512];
+	int len, i, j;
+	void *handle;
+	struct extension_handle_cb *ehc;
+
+	for (i = 0; i < extension_opts_len; i++) {
+		handle = NULL;
+		if (!extension_opts[i])
+			continue;
+		if ((len = strlen(extension_opts[i])) <= 3 ||
+		    (strcmp(extension_opts[i] + len - 3, ".so") != 0)) {
+			ERRMSG("Skip invalid extension: %s\n", extension_opts[i]);
+			continue;
+		}
+
+		if (extension_opts[i][0] == '/') {
+			/* Path & filename */
+			snprintf(path, sizeof(path), "%s", extension_opts[i]);
+			handle = dlopen(path, RTLD_NOW);
+			if (!handle) {
+				ERRMSG("Failed to load %s\n", dlerror());
+				continue;
+			}
+		} else {
+			/* Only filename */
+			for (j = 0; j < sizeof(dirs) / sizeof(char *); j++) {
+				snprintf(path, sizeof(path), "%s", dirs[j]);
+				len = strlen(path);
+				snprintf(path + len, sizeof(path) - len, "%s",
+					extension_opts[i]);
+				if (access(path, F_OK) == 0) {
+					handle = dlopen(path, RTLD_NOW);
+					if (handle)
+						break;
+					else
+						ERRMSG("Failed to load %s\n", dlerror());
+				}
+			}
+			if (!handle && j >= sizeof(dirs) / sizeof(char *)) {
+				ERRMSG("Not found %s\n", extension_opts[i]);
+				continue;
+			}
+		}
+
+		if (dlsym(handle, "extension_init") == NULL) {
+			ERRMSG("Skip extension %s: No extension_init()\n", path);
+			dlclose(handle);
+			continue;
+		}
+
+		if ((ehc = malloc(sizeof(struct extension_handle_cb))) == NULL) {
+			ERRMSG("Skip extension %s: No memory\n", path);
+			dlclose(handle);
+			continue;
+		}
+
+		ehc->handle = handle;
+		ehc->cb = dlsym(handle, "extension_callback");
+
+		if (!add_to_arr((void ***)&handle_cbs, &handle_cbs_len, &handle_cbs_cap, ehc)) {
+			ERRMSG("Failed to load %s\n", extension_opts[i]);
+			free(ehc);
+			dlclose(handle);
+			continue;
+		}
+		MSG("Loaded extension: %s\n", path);
+	}
+}
+
+static bool register_ksyms_ktypes_sections(void)
+{
+	char *start, *stop;
+	int i;
+	bool ret = false;
+
+	for (i = 0; i < handle_cbs_len; i++) {
+		start = dlsym(handle_cbs[i]->handle, "__start_init_ksyms");
+		stop = dlsym(handle_cbs[i]->handle, "__stop_init_ksyms");
+		if (!register_ksym_section(start, stop))
+			goto out;
+
+		start = dlsym(handle_cbs[i]->handle, "__start_init_ktypes");
+		stop = dlsym(handle_cbs[i]->handle, "__stop_init_ktypes");
+		if (!register_ktype_section(start, stop))
+			goto out;
+	}
+	/* If no extensions, don't register makedumpfile's section */
+	if (handle_cbs_len > 0) {
+		start = dlsym(NULL, "__start_init_ksyms");
+		stop = dlsym(NULL, "__stop_init_ksyms");
+		if (!register_ksym_section(start, stop))
+			goto out;
+
+		start = dlsym(NULL, "__start_init_ktypes");
+		stop = dlsym(NULL, "__stop_init_ktypes");
+		if (!register_ktype_section(start, stop))
+			goto out;
+	}
+	ret = true;
+out:
+	return ret;
+}
+
+void cleanup_extensions(void)
+{
+	for (int i = 0; i < handle_cbs_len; i++) {
+		dlclose(handle_cbs[i]->handle);
+		free(handle_cbs[i]);
+	}
+	if (handle_cbs) {
+		free(handle_cbs);
+		handle_cbs = NULL;
+	}
+	handle_cbs_len = 0;
+	handle_cbs_cap = 0;
+	if (extension_opts) {
+		free(extension_opts);
+		extension_opts = NULL;
+	}
+	extension_opts_len = 0;
+	extension_opts_cap = 0;
+
+	cleanup_kallsyms_btf();
+}
+
+static bool check_required_ksyms_all_resolved(void *handle)
+{
+	char *start, *stop;
+	struct ksym_info **p;
+	bool ret = true;
+
+	start = dlsym(handle, "__start_init_ksyms");
+	stop = dlsym(handle, "__stop_init_ksyms");
+
+	for (p = (struct ksym_info **)start;
+	     p < (struct ksym_info **)stop;
+	     p++) {
+		if ((*p)->sym_required && !SYM_EXIST(*p)) {
+			ret = false;
+			ERRMSG("Symbol %s in %s not found\n",
+				(*p)->symname, (*p)->modname);
+		}
+	}
+
+	return ret;
+}
+
+static bool check_required_ktypes_all_resolved(void *handle)
+{
+	char *start, *stop;
+	struct ktype_info **p;
+	bool ret = true;
+
+	start = dlsym(handle, "__start_init_ktypes");
+	stop = dlsym(handle, "__stop_init_ktypes");
+
+	for (p = (struct ktype_info **)start;
+	     p < (struct ktype_info **)stop;
+	     p++) {
+		if (!TYPE_EXIST(*p)) {
+			if ((*p)->member_required) {
+				ret = false;
+				ERRMSG("Member %s of struct %s in %s not found\n",
+					(*p)->member_name, (*p)->struct_name,
+					(*p)->modname);
+			} else if ((*p)->struct_required) {
+				ret = false;
+				ERRMSG("Struct %s in %s not found\n",
+					(*p)->struct_name, (*p)->modname);
+			}
+		}
+	}
+
+	return ret;
+}
+
+static bool extension_runnable(void *handle)
+{
+	return check_required_ksyms_all_resolved(handle) &&
+		check_required_ktypes_all_resolved(handle);
+}
+
+void init_extensions(void)
+{
+	/* Entry of extension init */
+	void (*init)(void);
+
+	load_extensions();
+	if (!register_ksyms_ktypes_sections())
+		goto fail;
+	if (!init_kallsyms_btf()) 
+		goto fail;
+	for (int i = 0; i < handle_cbs_len; i++) {
+		if (extension_runnable(handle_cbs[i]->handle)) {
+			init = dlsym(handle_cbs[i]->handle, "extension_init");
+			init();
+		} else {
+			/*
+			* Skip init() & reset callback for the
+			* un-runnable extension
+			*/
+			handle_cbs[i]->cb = NULL;
+			ERRMSG("Skip %dth extension\n", i + 1);
+		}
+	}
+	return;
+fail:
+	ERRMSG("fail & skip all extensions\n");
+	cleanup_extensions();
+}
+
+/*
+ * For a single pfn/pcache, multiple extensions will decide whether to:
+ * 1) include the page (PG_INCLUDE), or
+ * 2) exclude the page (PG_EXCLUDE), or
+ * 3) make no decision to pass to others or fallback to traditional page-flags
+ *    based filtering (PG_UNDECID).
+ * 
+ * The arbitration is:
+ * 1) Include the page if anyone says PG_INCLUDE, and
+ * 2) Exclude the page if no one says PG_INCLUDE, but one or more say PG_EXCLUDE.
+ */
+int run_extension_callback(unsigned long pfn, const void *pcache)
+{
+	int result;
+	int ret = PG_UNDECID;
+
+	for (int i = 0; i < handle_cbs_len; i++) {
+		if (handle_cbs[i]->cb) {
+			result = handle_cbs[i]->cb(pfn, pcache);
+			if (result == PG_INCLUDE) {
+				ret = result;
+				goto out;
+			} else if (result == PG_EXCLUDE) {
+				ret = result;
+			}
+		}
+	}
+out:
+	return ret;
+}
+
+bool extension_has_callback(void)
+{
+	return handle_cbs_len > 0;
+}
+
+#else /* EXTENSION */
+
+void init_extensions(void) { }
+void cleanup_extensions(void) { }
+bool add_extension_opts(char *opt)
+{
+	ERRMSG("extension unsupported. Try `make EXTENSION=on` when building\n");
+	return false;
+}
+
+int run_extension_callback(unsigned long pfn, const void *pcache)
+{
+	return PG_UNDECID;
+}
+
+bool extension_has_callback(void)
+{
+	return false;
+}
+
+#endif /* EXTENSION */
+
diff --git a/extension.h b/extension.h
new file mode 100644
index 0000000..ba8d32a
--- /dev/null
+++ b/extension.h
@@ -0,0 +1,16 @@
+#ifndef _EXTENSION_H
+#define _EXTENSION_H
+#include <stdbool.h>
+
+enum {
+	PG_INCLUDE,	// Exntesion will keep the page
+	PG_EXCLUDE,	// Exntesion will discard the page
+	PG_UNDECID,	// Exntesion makes no decision
+};
+int run_extension_callback(unsigned long pfn, const void *pcache);
+void init_extensions(void);
+void cleanup_extensions(void);
+bool add_extension_opts(char *opt);
+bool extension_has_callback(void);
+#endif /* _EXTENSION_H */
+
diff --git a/extensions/Makefile b/extensions/Makefile
new file mode 100644
index 0000000..b23f346
--- /dev/null
+++ b/extensions/Makefile
@@ -0,0 +1,11 @@
+CC ?= gcc
+CONTRIB_SO :=
+
+all: $(CONTRIB_SO)
+
+$(CONTRIB_SO): %.so: %.c
+	$(CC) -O2 -g -fPIC -shared -Wl,-T,../makedumpfile.ld -o $@ $^
+
+clean:
+	rm -f $(CONTRIB_SO)
+
diff --git a/makedumpfile.c b/makedumpfile.c
index 53a8812..46d9ac7 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -28,6 +28,7 @@
 #include <assert.h>
 #include <zlib.h>
 #include "kallsyms.h"
+#include "extension.h"
 
 struct symbol_table	symbol_table;
 struct size_table	size_table;
@@ -102,6 +103,7 @@ mdf_pfn_t pfn_free;
 mdf_pfn_t pfn_hwpoison;
 mdf_pfn_t pfn_offline;
 mdf_pfn_t pfn_elf_excluded;
+mdf_pfn_t pfn_extension;
 
 mdf_pfn_t num_dumped;
 
@@ -6468,6 +6470,7 @@ __exclude_unnecessary_pages(unsigned long mem_map,
 	unsigned int order_offset, dtor_offset;
 	unsigned long flags, mapping, private = 0;
 	unsigned long compound_dtor, compound_head = 0;
+	int filter_pg;
 
 	/*
 	 * If a multi-page exclusion is pending, do it first
@@ -6540,6 +6543,14 @@ __exclude_unnecessary_pages(unsigned long mem_map,
 			pfn_read_end   = pfn + pfn_mm - 1;
 		}
 
+		/*
+		 * Include pages that specified by user via
+		 * makedumpfile extensions
+		 */
+		filter_pg = run_extension_callback(pfn, pcache);
+		if (filter_pg == PG_INCLUDE)
+			continue;
+
 		flags   = ULONG(pcache + OFFSET(page.flags));
 		_count  = UINT(pcache + OFFSET(page._refcount));
 		mapping = ULONG(pcache + OFFSET(page.mapping));
@@ -6696,6 +6707,14 @@ check_order:
 		else if (isOffline(flags, _mapcount)) {
 			pfn_counter = &pfn_offline;
 		}
+		/*
+		 * Exclude pages that specified by user via
+		 * makedumpfile extensions
+		 */
+		else if (filter_pg == PG_EXCLUDE) {
+			nr_pages = 1;
+			pfn_counter = &pfn_extension;
+		}
 		/*
 		 * Unexcludable page
 		 */
@@ -7182,13 +7201,14 @@ create_2nd_bitmap(struct cycle *cycle)
 
 	/*
 	 * Exclude cache pages, cache private pages, user data pages,
-	 * and hwpoison pages.
+	 * hwpoison pages and extension specified pages.
 	 */
 	if (info->dump_level & DL_EXCLUDE_CACHE ||
 	    info->dump_level & DL_EXCLUDE_CACHE_PRI ||
 	    info->dump_level & DL_EXCLUDE_USER_DATA ||
 	    NUMBER(PG_hwpoison) != NOT_FOUND_NUMBER ||
-	    ((info->dump_level & DL_EXCLUDE_FREE) && info->page_is_buddy)) {
+	    ((info->dump_level & DL_EXCLUDE_FREE) && info->page_is_buddy) ||
+	    extension_has_callback()) {
 		if (!exclude_unnecessary_pages(cycle)) {
 			ERRMSG("Can't exclude unnecessary pages.\n");
 			return FALSE;
@@ -8243,7 +8263,7 @@ write_elf_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_page)
 	 */
 	if (info->flag_cyclic) {
 		pfn_zero = pfn_cache = pfn_cache_private = 0;
-		pfn_user = pfn_free = pfn_hwpoison = pfn_offline = 0;
+		pfn_user = pfn_free = pfn_hwpoison = pfn_offline = pfn_extension = 0;
 		pfn_memhole = info->max_mapnr;
 	}
 
@@ -9588,7 +9608,7 @@ write_kdump_pages_and_bitmap_cyclic(struct cache_data *cd_header, struct cache_d
 		 * Reset counter for debug message.
 		 */
 		pfn_zero = pfn_cache = pfn_cache_private = 0;
-		pfn_user = pfn_free = pfn_hwpoison = pfn_offline = 0;
+		pfn_user = pfn_free = pfn_hwpoison = pfn_offline = pfn_extension = 0;
 		pfn_memhole = info->max_mapnr;
 
 		/*
@@ -10537,7 +10557,7 @@ print_report(void)
 	pfn_original = info->max_mapnr - pfn_memhole;
 
 	pfn_excluded = pfn_zero + pfn_cache + pfn_cache_private
-	    + pfn_user + pfn_free + pfn_hwpoison + pfn_offline;
+	    + pfn_user + pfn_free + pfn_hwpoison + pfn_offline + pfn_extension;
 
 	REPORT_MSG("\n");
 	REPORT_MSG("Original pages  : 0x%016llx\n", pfn_original);
@@ -10553,6 +10573,7 @@ print_report(void)
 	REPORT_MSG("    Free pages              : 0x%016llx\n", pfn_free);
 	REPORT_MSG("    Hwpoison pages          : 0x%016llx\n", pfn_hwpoison);
 	REPORT_MSG("    Offline pages           : 0x%016llx\n", pfn_offline);
+	REPORT_MSG("    Extension filter pages  : 0x%016llx\n", pfn_extension);
 	REPORT_MSG("  Remaining pages  : 0x%016llx\n",
 	    pfn_original - pfn_excluded);
 
@@ -10593,7 +10614,7 @@ print_mem_usage(void)
 	pfn_original = info->max_mapnr - pfn_memhole;
 
 	pfn_excluded = pfn_zero + pfn_cache + pfn_cache_private
-	    + pfn_user + pfn_free + pfn_hwpoison + pfn_offline;
+	    + pfn_user + pfn_free + pfn_hwpoison + pfn_offline + pfn_extension;
 	shrinking = (pfn_original - pfn_excluded) * 100;
 	shrinking = shrinking / pfn_original;
 	total_size = info->page_size * pfn_original;
@@ -10887,6 +10908,7 @@ create_dumpfile(void)
 	}
 
 	print_vtop();
+	init_extensions();
 
 	num_retry = 0;
 retry:
@@ -10930,6 +10952,7 @@ retry:
 	}
 	print_report();
 
+	cleanup_extensions();
 	clear_filter_info();
 	if (!close_files_for_creating_dumpfile())
 		return FALSE;
@@ -12139,6 +12162,7 @@ static struct option longopts[] = {
 	{"check-params", no_argument, NULL, OPT_CHECK_PARAMS},
 	{"dry-run", no_argument, NULL, OPT_DRY_RUN},
 	{"show-stats", no_argument, NULL, OPT_SHOW_STATS},
+	{"extension", required_argument, NULL, OPT_EXTENSION},
 	{0, 0, 0, 0}
 };
 
@@ -12326,6 +12350,11 @@ main(int argc, char *argv[])
 		case OPT_SHOW_STATS:
 			flag_show_stats = TRUE;
 			break;
+		case OPT_EXTENSION:
+			if (add_extension_opts(optarg))
+				break;
+			else
+				goto out;
 		case '?':
 			MSG("Commandline parameter is invalid.\n");
 			MSG("Try `makedumpfile --help' for more information.\n");
diff --git a/makedumpfile.h b/makedumpfile.h
index 19bb6a5..4f707c7 100644
--- a/makedumpfile.h
+++ b/makedumpfile.h
@@ -2747,6 +2747,7 @@ struct elf_prstatus {
 #define OPT_CHECK_PARAMS        OPT_START+18
 #define OPT_DRY_RUN             OPT_START+19
 #define OPT_SHOW_STATS          OPT_START+20
+#define OPT_EXTENSION           OPT_START+21
 
 /*
  * Function Prototype.
-- 
2.54.0