[PATCH v3 5/8] Add makedumpfile extension support

[Tao Liu]

This patch will add .so extension support to makedumpfile, similar to crash
extension to crash utility. Currently only "/usr/lib64/makedumpfile/extensions"
and "./extensions" are searched for extensions. Once found, kallsyms and btf
will be initialized so all extensions can benifit from it (Currently makedumpfile
doesn't use these info, we can move the kallsyms/btf init code else where later
if makedumpfile needs them).

The makedumpfile extension is to help users to customize mm page filtering upon
traditional mm page flag filtering, without make code modification on makedumpfile
itself.

Signed-off-by: Tao Liu <ltao at redhat.com>
---
 Makefile            |  7 +++-
 extension.c         | 82 +++++++++++++++++++++++++++++++++++++++++++++
 extensions/Makefile | 10 ++++++
 makedumpfile.c      |  4 +++
 4 files changed, 102 insertions(+), 1 deletion(-)
 create mode 100644 extension.c
 create mode 100644 extensions/Makefile

diff --git a/Makefile b/Makefile
index f3f4da8..7e29220 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))
@@ -126,6 +126,7 @@ 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 +136,7 @@ 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)
\ No newline at end of file
diff --git a/extension.c b/extension.c
new file mode 100644
index 0000000..6ee7f4e
--- /dev/null
+++ b/extension.c
@@ -0,0 +1,82 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <dirent.h>
+#include <dlfcn.h>
+#include <stdbool.h>
+#include "kallsyms.h"
+#include "btf_info.h"
+
+static const char *dirs[] = {
+	"/usr/lib64/makedumpfile/extensions",
+	"./extensions",
+};
+
+/* Will only init once */
+static bool init_kallsyms_btf(void)
+{
+	static bool ret = false;
+	static bool has_inited = false;
+
+	if (has_inited)
+		goto out;
+	if (!init_kernel_kallsyms())
+		goto out;
+	if (!init_kernel_btf())
+		goto out;
+	if (!init_module_kallsyms())
+		goto out;
+	if (!init_module_btf())
+		goto out;
+	ret = true;
+out:
+	has_inited = true;
+	return ret;
+}
+
+static void cleanup_kallsyms_btf(void)
+{
+	cleanup_kallsyms();
+	cleanup_btf();
+}
+
+void run_extensions(void)
+{
+	DIR *dir;
+	struct dirent *entry;
+	size_t len;
+	int i;
+	void *handle;
+	char path[512];
+
+	for (i = 0; i < sizeof(dirs) / sizeof(char *); i++) {
+		if ((dir = opendir(dirs[i])) != NULL)
+			break;
+	}
+
+	if (!dir || i >= sizeof(dirs) / sizeof(char *))
+		/* No extensions found */
+		return;
+
+	while ((entry = readdir(dir)) != NULL) {
+		len = strlen(entry->d_name);
+		if (len > 3 && strcmp(entry->d_name + len - 3, ".so") == 0) {
+			/* Will only init when .so exist */
+			if (!init_kallsyms_btf())
+				goto out;
+
+			snprintf(path, sizeof(path), "%s/%s", dirs[i], entry->d_name);
+			handle = dlopen(path, RTLD_NOW);
+			if (!handle) {
+				fprintf(stderr, "%s: Failed to load %s: %s\n",
+					__func__, path, dlerror());
+				continue;
+			}
+			printf("Loaded extension: %s\n", path);
+			dlclose(handle);
+		}
+	}
+out:
+	closedir(dir);
+	cleanup_kallsyms_btf();
+}
\ No newline at end of file
diff --git a/extensions/Makefile b/extensions/Makefile
new file mode 100644
index 0000000..afbc61e
--- /dev/null
+++ b/extensions/Makefile
@@ -0,0 +1,10 @@
+CC ?= gcc
+CONTRIB_SO :=
+
+all: $(CONTRIB_SO)
+
+$(CONTRIB_SO): %.so: %.c
+	$(CC) -O2 -g -fPIC -shared -o $@ $^
+
+clean:
+	rm -f $(CONTRIB_SO)
diff --git a/makedumpfile.c b/makedumpfile.c
index dba3628..ca8ed8a 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -10847,6 +10847,8 @@ update_dump_level(void)
 	}
 }
 
+void run_extensions(void);
+
 int
 create_dumpfile(void)
 {
@@ -10884,6 +10886,8 @@ retry:
 	if (info->flag_refiltering)
 		update_dump_level();
 
+	run_extensions();
+
 	if ((info->name_filterconfig || info->name_eppic_config)
 			&& !gather_filter_info())
 		return FALSE;
-- 
2.47.0