[PATCH v4][makedumpfile 6/7] Add makedumpfile extensions support
Tao Liu
ltao at redhat.com
Tue Apr 14 04:27:49 PDT 2026
Hi Stephen,
On Fri, Apr 3, 2026 at 1:12 PM Stephen Brennan
<stephen.s.brennan at oracle.com> wrote:
>
> Tao Liu <ltao at redhat.com> writes:
> > 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_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; For
> > syms/types which defined via INIT_(...) 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 advice
> > whether the page should be included/excluded.
> >
> > Suggested-by: Stephen Brennan <stephen.s.brennan at oracle.com>
> > Signed-off-by: Tao Liu <ltao at redhat.com>
> > ---
> > Makefile | 7 +-
> > extension.c | 300 ++++++++++++++++++++++++++++++++++++++++++++
> > extension.h | 12 ++
> > extensions/Makefile | 10 ++
> > makedumpfile.c | 38 +++++-
> > makedumpfile.h | 2 +
>
> I think the manual page will need updating with this change.
> Documentation updates could probably be done in a separate patch, though.
Thanks for the suggestion, I have updated the doc in v5.
>
> > 6 files changed, 363 insertions(+), 6 deletions(-)
> > create mode 100644 extension.c
> > create mode 100644 extension.h
> > create mode 100644 extensions/Makefile
> >
> > diff --git a/Makefile b/Makefile
> > index 320677d..1bb67d9 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..35e2756
> > --- /dev/null
> > +++ b/extension.c
> > @@ -0,0 +1,300 @@
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <string.h>
> > +#include <dirent.h>
> > +#include <dlfcn.h>
> > +#include <stdbool.h>
> > +#include <unistd.h>
> > +#include "kallsyms.h"
> > +#include "btf_info.h"
> > +#include "extension.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[] = {
> > + "/usr/lib64/makedumpfile/extensions/",
> > + "./extensions/",
> > +};
> > +
> > +void 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.
> > + */
> > + fprintf(stderr, "%s: Fail to add extension %s\n", __func__, opt);
> > +}
> > +
> > +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)) {
> > + fprintf(stderr, "%s: Skip invalid extension: %s\n",
> > + __func__, 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) {
> > + fprintf(stderr, "%s: Failed to load %s\n",
> > + __func__, 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
> > + fprintf(stderr, "%s: Failed to load %s\n",
> > + __func__, dlerror());
> > + }
> > + }
> > + if (!handle && j >= sizeof(dirs) / sizeof(char *)) {
> > + fprintf(stderr, "%s: Not found %s\n",
> > + __func__, extension_opts[i]);
> > + continue;
> > + }
> > + }
> > +
> > + if (dlsym(handle, "extension_init") == NULL) {
> > + fprintf(stderr, "%s: Skip extension %s: No extension_init()\n",
> > + __func__, path);
> > + dlclose(handle);
> > + continue;
> > + }
> > +
> > + if ((ehc = malloc(sizeof(struct extension_handle_cb))) == NULL) {
> > + fprintf(stderr, "%s: Skip extension %s: No memory\n",
> > + __func__, 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)) {
> > + fprintf(stderr, "%s: Failed to load %s\n", __func__,
> > + extension_opts[i]);
> > + free(ehc);
> > + dlclose(handle);
> > + continue;
> > + }
> > + printf("Loaded extension: %s\n", path);
> > + }
> > +}
> > +
> > +static bool register_extension_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;
> > + }
> > + 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;
> > + fprintf(stderr, "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;
> > + fprintf(stderr, "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;
> > + fprintf(stderr, "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_extension_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 {
> > + fprintf(stderr, "%s: Skip %dth extension\n",
> > + __func__, i + 1);
> > + }
> > + }
> > + return;
> > +fail:
> > + fprintf(stderr, "%s: fail & skip all extensions\n", __func__);
> > + cleanup_extensions();
> > +}
> > +
> > +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;
> > +}
> > \ No newline at end of file
> > diff --git a/extension.h b/extension.h
> > new file mode 100644
> > index 0000000..dc5902e
> > --- /dev/null
> > +++ b/extension.h
> > @@ -0,0 +1,12 @@
> > +#ifndef _EXTENSION_H
> > +#define _EXTENSION_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);
> > +#endif /* _EXTENSION_H */
> > \ No newline at end of file
> > diff --git a/extensions/Makefile b/extensions/Makefile
> > new file mode 100644
> > index 0000000..b8bbfbc
> > --- /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 -Wl,-T,../makedumpfile.ld -o $@ $^
> > +
> > +clean:
> > + rm -f $(CONTRIB_SO)
> > \ No newline at end of file
> > diff --git a/makedumpfile.c b/makedumpfile.c
> > index dba3628..ef7468f 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;
> >
> > @@ -6459,6 +6461,7 @@ __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
> > @@ -6531,6 +6534,14 @@ __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));
> > @@ -6687,6 +6698,14 @@ 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
> > */
> > @@ -8234,7 +8253,7 @@ 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;
> > }
> >
> > @@ -9579,7 +9598,7 @@ 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;
> >
> > /*
> > @@ -10528,7 +10547,7 @@ 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);
> > @@ -10544,6 +10563,7 @@ 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);
> >
> > @@ -10584,7 +10604,7 @@ 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;
> > @@ -10878,6 +10898,7 @@ create_dumpfile(void)
> > }
> >
> > print_vtop();
> > + init_extensions();
> >
> > num_retry = 0;
> > retry:
> > @@ -10888,8 +10909,11 @@ retry:
> > && !gather_filter_info())
> > return FALSE;
> >
> > - if (!create_dump_bitmap())
> > + if (!create_dump_bitmap()) {
> > + cleanup_extensions();
> > return FALSE;
> > + }
> > + cleanup_extensions();
>
> If a retry happens, then all of the data related to extensions will be
> cleared: including the list of extensions, the callbacks, etc.
> Functionally, extensions will be disabled on the retry. Is that
> intentional?
>
> If not, then I think we'll need to move this cleanup so that it happens
> when we exit the retry loop (either by an early return, or on success).
>
> If this is intentional, then it probably ought to be documented.
Honestly I have missed the retry case, you're right the
cleanup_extension will break the retry. My initial thought was,
extensions will only be useful to create_dump_bitmap(), when it
finishes job, all extensions are better to be freed to save memory.
For writeout_dumpfile() will do page compression, which might take up
memory. But after my testing, free early or later don't really impact
memory consumption. So I simply take your implementation in v5.
Thanks,
Tao Liu
>
> Thanks,
> Stephen
>
> > if (info->flag_split) {
> > if ((status = writeout_multiple_dumpfiles()) == FALSE)
> > @@ -12130,6 +12154,7 @@ 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}
> > };
> >
> > @@ -12317,6 +12342,9 @@ main(int argc, char *argv[])
> > case OPT_SHOW_STATS:
> > flag_show_stats = TRUE;
> > break;
> > + case OPT_EXTENSION:
> > + add_extension_opts(optarg);
> > + break;
> > case '?':
> > MSG("Commandline parameter is invalid.\n");
> > MSG("Try `makedumpfile --help' for more information.\n");
> > diff --git a/makedumpfile.h b/makedumpfile.h
> > index 0f13743..d880ae7 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.
> > @@ -2777,5 +2778,6 @@ int write_and_check_space(int fd, void *buf, size_t buf_size,
> > int open_dump_file(void);
> > int dump_lockless_dmesg(void);
> > unsigned long long memparse(char *ptr, char **retptr);
> > +void add_extension_opts(char *opt);
> >
> > #endif /* MAKEDUMPFILE_H */
> > --
> > 2.47.0
>
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