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[34.86.47.53]) by smtp.gmail.com with ESMTPSA id 00721157ae682-785cd6edd87sm14099197b3.51.2025.10.24.09.10.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Oct 2025 09:10:05 -0700 (PDT) From: Pasha Tatashin To: akpm@linux-foundation.org, brauner@kernel.org, corbet@lwn.net, graf@amazon.com, jgg@ziepe.ca, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, masahiroy@kernel.org, ojeda@kernel.org, pasha.tatashin@soleen.com, pratyush@kernel.org, rdunlap@infradead.org, rppt@kernel.org, tj@kernel.org Subject: [PATCH v8 2/8] kho: make debugfs interface optional Date: Fri, 24 Oct 2025 12:09:56 -0400 Message-ID: <20251024161002.747372-3-pasha.tatashin@soleen.com> X-Mailer: git-send-email 2.51.1.821.gb6fe4d2222-goog In-Reply-To: <20251024161002.747372-1-pasha.tatashin@soleen.com> References: <20251024161002.747372-1-pasha.tatashin@soleen.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Currently, KHO is controlled via debugfs interface, but once LUO is introduced, it can control KHO, and the debug interface becomes optional. Add a separate config CONFIG_KEXEC_HANDOVER_DEBUGFS that enables the debugfs interface, and allows to inspect the tree. Move all debugfs related code to a new file to keep the .c files clear of ifdefs. Co-developed-by: Mike Rapoport (Microsoft) Signed-off-by: Mike Rapoport (Microsoft) Signed-off-by: Pasha Tatashin Reviewed-by: Pratyush Yadav --- MAINTAINERS | 3 +- kernel/Kconfig.kexec | 10 ++ kernel/Makefile | 1 + kernel/kexec_handover.c | 226 +++----------------------- kernel/kexec_handover_debugfs.c | 216 ++++++++++++++++++++++++ kernel/kexec_handover_internal.h | 37 +++++ tools/testing/selftests/kho/vmtest.sh | 1 + 7 files changed, 286 insertions(+), 208 deletions(-) create mode 100644 kernel/kexec_handover_debugfs.c diff --git a/MAINTAINERS b/MAINTAINERS index 5ea78444f035..35d7942b2082 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -13815,13 +13815,14 @@ KEXEC HANDOVER (KHO) M: Alexander Graf M: Mike Rapoport M: Changyuan Lyu +M: Pasha Tatashin L: kexec@lists.infradead.org L: linux-mm@kvack.org S: Maintained F: Documentation/admin-guide/mm/kho.rst F: Documentation/core-api/kho/* F: include/linux/kexec_handover.h -F: kernel/kexec_handover.c +F: kernel/kexec_handover* F: tools/testing/selftests/kho/ =20 KEYS-ENCRYPTED diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec index c94d36b5fcd9..9308a0fb1419 100644 --- a/kernel/Kconfig.kexec +++ b/kernel/Kconfig.kexec @@ -118,6 +118,16 @@ config KEXEC_HANDOVER_DEBUG scenarios and the extra code might be adding overhead it is only optionally enabled. =20 +config KEXEC_HANDOVER_DEBUGFS + bool "kexec handover debugfs interface" + depends on KEXEC_HANDOVER + depends on DEBUG_FS + help + Allow to control kexec handover device tree via debugfs + interface, i.e. finalize the state or aborting the finalization. + Also, enables inspecting the KHO fdt trees with the debugfs binary + blobs. + config CRASH_DUMP bool "kernel crash dumps" default ARCH_DEFAULT_CRASH_DUMP diff --git a/kernel/Makefile b/kernel/Makefile index 9fe722305c9b..2cf7909a74e5 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -84,6 +84,7 @@ obj-$(CONFIG_KEXEC_FILE) +=3D kexec_file.o obj-$(CONFIG_KEXEC_ELF) +=3D kexec_elf.o obj-$(CONFIG_KEXEC_HANDOVER) +=3D kexec_handover.o obj-$(CONFIG_KEXEC_HANDOVER_DEBUG) +=3D kexec_handover_debug.o +obj-$(CONFIG_KEXEC_HANDOVER_DEBUGFS) +=3D kexec_handover_debugfs.o obj-$(CONFIG_BACKTRACE_SELF_TEST) +=3D backtracetest.o obj-$(CONFIG_COMPAT) +=3D compat.o obj-$(CONFIG_CGROUPS) +=3D cgroup/ diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c index 6458f369a346..da071277d85e 100644 --- a/kernel/kexec_handover.c +++ b/kernel/kexec_handover.c @@ -11,7 +11,6 @@ #include #include #include -#include #include #include #include @@ -30,6 +29,7 @@ */ #include "../mm/internal.h" #include "kexec_internal.h" +#include "kexec_handover_internal.h" =20 #define KHO_FDT_COMPATIBLE "kho-v1" #define PROP_PRESERVED_MEMORY_MAP "preserved-memory-map" @@ -105,8 +105,6 @@ struct khoser_mem_chunk; =20 struct kho_serialization { struct page *fdt; - struct list_head fdt_list; - struct dentry *sub_fdt_dir; struct kho_mem_track track; /* First chunk of serialized preserved memory map */ struct khoser_mem_chunk *preserved_mem_map; @@ -114,20 +112,16 @@ struct kho_serialization { =20 struct kho_out { struct blocking_notifier_head chain_head; - - struct dentry *dir; - struct mutex lock; /* protects KHO FDT finalization */ - struct kho_serialization ser; bool finalized; + struct kho_debugfs dbg; }; =20 static struct kho_out kho_out =3D { .chain_head =3D BLOCKING_NOTIFIER_INIT(kho_out.chain_head), .lock =3D __MUTEX_INITIALIZER(kho_out.lock), .ser =3D { - .fdt_list =3D LIST_HEAD_INIT(kho_out.ser.fdt_list), .track =3D { .orders =3D XARRAY_INIT(kho_out.ser.track.orders, 0), }, @@ -477,8 +471,8 @@ static void __init kho_mem_deserialize(const void *fdt) * area for early allocations that happen before page allocator is * initialized. */ -static struct kho_scratch *kho_scratch; -static unsigned int kho_scratch_cnt; +struct kho_scratch *kho_scratch; +unsigned int kho_scratch_cnt; =20 /* * The scratch areas are scaled by default as percent of memory allocated = from @@ -674,37 +668,6 @@ static void __init kho_reserve_scratch(void) kho_enable =3D false; } =20 -struct fdt_debugfs { - struct list_head list; - struct debugfs_blob_wrapper wrapper; - struct dentry *file; -}; - -static int kho_debugfs_fdt_add(struct list_head *list, struct dentry *dir, - const char *name, const void *fdt) -{ - struct fdt_debugfs *f; - struct dentry *file; - - f =3D kmalloc(sizeof(*f), GFP_KERNEL); - if (!f) - return -ENOMEM; - - f->wrapper.data =3D (void *)fdt; - f->wrapper.size =3D fdt_totalsize(fdt); - - file =3D debugfs_create_blob(name, 0400, dir, &f->wrapper); - if (IS_ERR(file)) { - kfree(f); - return PTR_ERR(file); - } - - f->file =3D file; - list_add(&f->list, list); - - return 0; -} - /** * kho_add_subtree - record the physical address of a sub FDT in KHO root = tree. * @ser: serialization control object passed by KHO notifiers. @@ -716,7 +679,8 @@ static int kho_debugfs_fdt_add(struct list_head *list, = struct dentry *dir, * by KHO for the new kernel to retrieve it after kexec. * * A debugfs blob entry is also created at - * ``/sys/kernel/debug/kho/out/sub_fdts/@name``. + * ``/sys/kernel/debug/kho/out/sub_fdts/@name`` when kernel is configured = with + * CONFIG_KEXEC_HANDOVER_DEBUGFS * * Return: 0 on success, error code on failure */ @@ -733,7 +697,7 @@ int kho_add_subtree(struct kho_serialization *ser, cons= t char *name, void *fdt) if (err) return err; =20 - return kho_debugfs_fdt_add(&ser->fdt_list, ser->sub_fdt_dir, name, fdt); + return kho_debugfs_fdt_add(&kho_out.dbg, name, fdt, false); } EXPORT_SYMBOL_GPL(kho_add_subtree); =20 @@ -1064,29 +1028,6 @@ void *kho_restore_vmalloc(const struct kho_vmalloc *= preservation) } EXPORT_SYMBOL_GPL(kho_restore_vmalloc); =20 -/* Handling for debug/kho/out */ - -static struct dentry *debugfs_root; - -static int kho_out_update_debugfs_fdt(void) -{ - int err =3D 0; - struct fdt_debugfs *ff, *tmp; - - if (kho_out.finalized) { - err =3D kho_debugfs_fdt_add(&kho_out.ser.fdt_list, kho_out.dir, - "fdt", page_to_virt(kho_out.ser.fdt)); - } else { - list_for_each_entry_safe(ff, tmp, &kho_out.ser.fdt_list, list) { - debugfs_remove(ff->file); - list_del(&ff->list); - kfree(ff); - } - } - - return err; -} - static int __kho_abort(void) { int err; @@ -1136,8 +1077,9 @@ int kho_abort(void) return ret; =20 kho_out.finalized =3D false; + kho_debugfs_cleanup(&kho_out.dbg); =20 - return kho_out_update_debugfs_fdt(); + return 0; } =20 static int __kho_finalize(void) @@ -1206,92 +1148,23 @@ int kho_finalize(void) =20 kho_out.finalized =3D true; =20 - return kho_out_update_debugfs_fdt(); + return kho_debugfs_fdt_add(&kho_out.dbg, "fdt", + page_to_virt(kho_out.ser.fdt), true); } =20 -static int kho_out_finalize_get(void *data, u64 *val) +bool kho_finalized(void) { - mutex_lock(&kho_out.lock); - *val =3D kho_out.finalized; - mutex_unlock(&kho_out.lock); - - return 0; -} - -static int kho_out_finalize_set(void *data, u64 val) -{ - if (val) - return kho_finalize(); - else - return kho_abort(); -} - -DEFINE_DEBUGFS_ATTRIBUTE(fops_kho_out_finalize, kho_out_finalize_get, - kho_out_finalize_set, "%llu\n"); - -static int scratch_phys_show(struct seq_file *m, void *v) -{ - for (int i =3D 0; i < kho_scratch_cnt; i++) - seq_printf(m, "0x%llx\n", kho_scratch[i].addr); - - return 0; -} -DEFINE_SHOW_ATTRIBUTE(scratch_phys); - -static int scratch_len_show(struct seq_file *m, void *v) -{ - for (int i =3D 0; i < kho_scratch_cnt; i++) - seq_printf(m, "0x%llx\n", kho_scratch[i].size); - - return 0; -} -DEFINE_SHOW_ATTRIBUTE(scratch_len); - -static __init int kho_out_debugfs_init(void) -{ - struct dentry *dir, *f, *sub_fdt_dir; - - dir =3D debugfs_create_dir("out", debugfs_root); - if (IS_ERR(dir)) - return -ENOMEM; - - sub_fdt_dir =3D debugfs_create_dir("sub_fdts", dir); - if (IS_ERR(sub_fdt_dir)) - goto err_rmdir; - - f =3D debugfs_create_file("scratch_phys", 0400, dir, NULL, - &scratch_phys_fops); - if (IS_ERR(f)) - goto err_rmdir; - - f =3D debugfs_create_file("scratch_len", 0400, dir, NULL, - &scratch_len_fops); - if (IS_ERR(f)) - goto err_rmdir; - - f =3D debugfs_create_file("finalize", 0600, dir, NULL, - &fops_kho_out_finalize); - if (IS_ERR(f)) - goto err_rmdir; - - kho_out.dir =3D dir; - kho_out.ser.sub_fdt_dir =3D sub_fdt_dir; - return 0; - -err_rmdir: - debugfs_remove_recursive(dir); - return -ENOENT; + guard(mutex)(&kho_out.lock); + return kho_out.finalized; } =20 struct kho_in { - struct dentry *dir; phys_addr_t fdt_phys; phys_addr_t scratch_phys; - struct list_head fdt_list; + struct kho_debugfs dbg; }; =20 static struct kho_in kho_in =3D { - .fdt_list =3D LIST_HEAD_INIT(kho_in.fdt_list), }; =20 static const void *kho_get_fdt(void) @@ -1355,56 +1228,6 @@ int kho_retrieve_subtree(const char *name, phys_addr= _t *phys) } EXPORT_SYMBOL_GPL(kho_retrieve_subtree); =20 -/* Handling for debugfs/kho/in */ - -static __init int kho_in_debugfs_init(const void *fdt) -{ - struct dentry *sub_fdt_dir; - int err, child; - - kho_in.dir =3D debugfs_create_dir("in", debugfs_root); - if (IS_ERR(kho_in.dir)) - return PTR_ERR(kho_in.dir); - - sub_fdt_dir =3D debugfs_create_dir("sub_fdts", kho_in.dir); - if (IS_ERR(sub_fdt_dir)) { - err =3D PTR_ERR(sub_fdt_dir); - goto err_rmdir; - } - - err =3D kho_debugfs_fdt_add(&kho_in.fdt_list, kho_in.dir, "fdt", fdt); - if (err) - goto err_rmdir; - - fdt_for_each_subnode(child, fdt, 0) { - int len =3D 0; - const char *name =3D fdt_get_name(fdt, child, NULL); - const u64 *fdt_phys; - - fdt_phys =3D fdt_getprop(fdt, child, "fdt", &len); - if (!fdt_phys) - continue; - if (len !=3D sizeof(*fdt_phys)) { - pr_warn("node `%s`'s prop `fdt` has invalid length: %d\n", - name, len); - continue; - } - err =3D kho_debugfs_fdt_add(&kho_in.fdt_list, sub_fdt_dir, name, - phys_to_virt(*fdt_phys)); - if (err) { - pr_warn("failed to add fdt `%s` to debugfs: %d\n", name, - err); - continue; - } - } - - return 0; - -err_rmdir: - debugfs_remove_recursive(kho_in.dir); - return err; -} - static __init int kho_init(void) { int err =3D 0; @@ -1419,27 +1242,16 @@ static __init int kho_init(void) goto err_free_scratch; } =20 - debugfs_root =3D debugfs_create_dir("kho", NULL); - if (IS_ERR(debugfs_root)) { - err =3D -ENOENT; + err =3D kho_debugfs_init(); + if (err) goto err_free_fdt; - } =20 - err =3D kho_out_debugfs_init(); + err =3D kho_out_debugfs_init(&kho_out.dbg); if (err) goto err_free_fdt; =20 if (fdt) { - err =3D kho_in_debugfs_init(fdt); - /* - * Failure to create /sys/kernel/debug/kho/in does not prevent - * reviving state from KHO and setting up KHO for the next - * kexec. - */ - if (err) - pr_err("failed exposing handover FDT in debugfs: %d\n", - err); - + kho_in_debugfs_init(&kho_in.dbg, fdt); return 0; } =20 diff --git a/kernel/kexec_handover_debugfs.c b/kernel/kexec_handover_debugf= s.c new file mode 100644 index 000000000000..a91b279f1b23 --- /dev/null +++ b/kernel/kexec_handover_debugfs.c @@ -0,0 +1,216 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * kexec_handover_debugfs.c - kexec handover debugfs interfaces + * Copyright (C) 2023 Alexander Graf + * Copyright (C) 2025 Microsoft Corporation, Mike Rapoport + * Copyright (C) 2025 Google LLC, Changyuan Lyu + * Copyright (C) 2025 Google LLC, Pasha Tatashin + */ + +#define pr_fmt(fmt) "KHO: " fmt + +#include +#include +#include +#include +#include "kexec_handover_internal.h" + +static struct dentry *debugfs_root; + +struct fdt_debugfs { + struct list_head list; + struct debugfs_blob_wrapper wrapper; + struct dentry *file; +}; + +static int __kho_debugfs_fdt_add(struct list_head *list, struct dentry *di= r, + const char *name, const void *fdt) +{ + struct fdt_debugfs *f; + struct dentry *file; + + f =3D kmalloc(sizeof(*f), GFP_KERNEL); + if (!f) + return -ENOMEM; + + f->wrapper.data =3D (void *)fdt; + f->wrapper.size =3D fdt_totalsize(fdt); + + file =3D debugfs_create_blob(name, 0400, dir, &f->wrapper); + if (IS_ERR(file)) { + kfree(f); + return PTR_ERR(file); + } + + f->file =3D file; + list_add(&f->list, list); + + return 0; +} + +int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name, + const void *fdt, bool root) +{ + struct dentry *dir; + + if (root) + dir =3D dbg->dir; + else + dir =3D dbg->sub_fdt_dir; + + return __kho_debugfs_fdt_add(&dbg->fdt_list, dir, name, fdt); +} + +void kho_debugfs_cleanup(struct kho_debugfs *dbg) +{ + struct fdt_debugfs *ff, *tmp; + + list_for_each_entry_safe(ff, tmp, &dbg->fdt_list, list) { + debugfs_remove(ff->file); + list_del(&ff->list); + kfree(ff); + } +} + +static int kho_out_finalize_get(void *data, u64 *val) +{ + *val =3D kho_finalized(); + + return 0; +} + +static int kho_out_finalize_set(void *data, u64 val) +{ + if (val) + return kho_finalize(); + else + return kho_abort(); +} + +DEFINE_DEBUGFS_ATTRIBUTE(kho_out_finalize_fops, kho_out_finalize_get, + kho_out_finalize_set, "%llu\n"); + +static int scratch_phys_show(struct seq_file *m, void *v) +{ + for (int i =3D 0; i < kho_scratch_cnt; i++) + seq_printf(m, "0x%llx\n", kho_scratch[i].addr); + + return 0; +} +DEFINE_SHOW_ATTRIBUTE(scratch_phys); + +static int scratch_len_show(struct seq_file *m, void *v) +{ + for (int i =3D 0; i < kho_scratch_cnt; i++) + seq_printf(m, "0x%llx\n", kho_scratch[i].size); + + return 0; +} +DEFINE_SHOW_ATTRIBUTE(scratch_len); + +__init void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt) +{ + struct dentry *dir, *sub_fdt_dir; + int err, child; + + INIT_LIST_HEAD(&dbg->fdt_list); + + dir =3D debugfs_create_dir("in", debugfs_root); + if (IS_ERR(dir)) { + err =3D PTR_ERR(dir); + goto err_out; + } + + sub_fdt_dir =3D debugfs_create_dir("sub_fdts", dir); + if (IS_ERR(sub_fdt_dir)) { + err =3D PTR_ERR(sub_fdt_dir); + goto err_rmdir; + } + + err =3D __kho_debugfs_fdt_add(&dbg->fdt_list, dir, "fdt", fdt); + if (err) + goto err_rmdir; + + fdt_for_each_subnode(child, fdt, 0) { + int len =3D 0; + const char *name =3D fdt_get_name(fdt, child, NULL); + const u64 *fdt_phys; + + fdt_phys =3D fdt_getprop(fdt, child, "fdt", &len); + if (!fdt_phys) + continue; + if (len !=3D sizeof(*fdt_phys)) { + pr_warn("node %s prop fdt has invalid length: %d\n", + name, len); + continue; + } + err =3D __kho_debugfs_fdt_add(&dbg->fdt_list, sub_fdt_dir, name, + phys_to_virt(*fdt_phys)); + if (err) { + pr_warn("failed to add fdt %s to debugfs: %d\n", name, + err); + continue; + } + } + + dbg->dir =3D dir; + dbg->sub_fdt_dir =3D sub_fdt_dir; + + return; +err_rmdir: + debugfs_remove_recursive(dir); +err_out: + /* + * Failure to create /sys/kernel/debug/kho/in does not prevent + * reviving state from KHO and setting up KHO for the next + * kexec. + */ + if (err) + pr_err("failed exposing handover FDT in debugfs: %d\n", err); +} + +__init int kho_out_debugfs_init(struct kho_debugfs *dbg) +{ + struct dentry *dir, *f, *sub_fdt_dir; + + INIT_LIST_HEAD(&dbg->fdt_list); + + dir =3D debugfs_create_dir("out", debugfs_root); + if (IS_ERR(dir)) + return -ENOMEM; + + sub_fdt_dir =3D debugfs_create_dir("sub_fdts", dir); + if (IS_ERR(sub_fdt_dir)) + goto err_rmdir; + + f =3D debugfs_create_file("scratch_phys", 0400, dir, NULL, + &scratch_phys_fops); + if (IS_ERR(f)) + goto err_rmdir; + + f =3D debugfs_create_file("scratch_len", 0400, dir, NULL, + &scratch_len_fops); + if (IS_ERR(f)) + goto err_rmdir; + + f =3D debugfs_create_file("finalize", 0600, dir, NULL, + &kho_out_finalize_fops); + if (IS_ERR(f)) + goto err_rmdir; + + dbg->dir =3D dir; + dbg->sub_fdt_dir =3D sub_fdt_dir; + return 0; + +err_rmdir: + debugfs_remove_recursive(dir); + return -ENOENT; +} + +__init int kho_debugfs_init(void) +{ + debugfs_root =3D debugfs_create_dir("kho", NULL); + if (IS_ERR(debugfs_root)) + return -ENOENT; + return 0; +} diff --git a/kernel/kexec_handover_internal.h b/kernel/kexec_handover_inter= nal.h index 05e9720ba7b9..28c0e971613d 100644 --- a/kernel/kexec_handover_internal.h +++ b/kernel/kexec_handover_internal.h @@ -2,8 +2,45 @@ #ifndef LINUX_KEXEC_HANDOVER_INTERNAL_H #define LINUX_KEXEC_HANDOVER_INTERNAL_H =20 +#include +#include #include =20 +#ifdef CONFIG_KEXEC_HANDOVER_DEBUGFS +#include + +struct kho_debugfs { + struct dentry *dir; + struct dentry *sub_fdt_dir; + struct list_head fdt_list; +}; + +#else +struct kho_debugfs {}; +#endif + +extern struct kho_scratch *kho_scratch; +extern unsigned int kho_scratch_cnt; + +bool kho_finalized(void); + +#ifdef CONFIG_KEXEC_HANDOVER_DEBUGFS +int kho_debugfs_init(void); +void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt); +int kho_out_debugfs_init(struct kho_debugfs *dbg); +int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name, + const void *fdt, bool root); +void kho_debugfs_cleanup(struct kho_debugfs *dbg); +#else +static inline int kho_debugfs_init(void) { return 0; } +static inline void kho_in_debugfs_init(struct kho_debugfs *dbg, + const void *fdt) { } +static inline int kho_out_debugfs_init(struct kho_debugfs *dbg) { return 0= ; } +static inline int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char = *name, + const void *fdt, bool root) { return 0; } +static inline void kho_debugfs_cleanup(struct kho_debugfs *dbg) {} +#endif /* CONFIG_KEXEC_HANDOVER_DEBUGFS */ + #ifdef CONFIG_KEXEC_HANDOVER_DEBUG bool kho_scratch_overlap(phys_addr_t phys, size_t size); #else diff --git a/tools/testing/selftests/kho/vmtest.sh b/tools/testing/selftest= s/kho/vmtest.sh index 3f6c17166846..49fdac8e8b15 100755 --- a/tools/testing/selftests/kho/vmtest.sh +++ b/tools/testing/selftests/kho/vmtest.sh @@ -59,6 +59,7 @@ function build_kernel() { tee "$kconfig" > "$kho_config" <