September 2025 - Crash-utility - Crash Utility List Archives

[PATCH] Fix "mount <address>" and MNT_CURSOR entries.

by Aureau, Georges (Kernel Tools ERT)

Fix "mount <address>" and MNT_CURSOR entries: 1/ "mount <address>" is failing on kernels without "super_block.s_files": crash> mount ff35d61d80200000 mount: the super_block.s_files linked list does not exist in this kernel mount: -f option not supported or applicable on this architecture or kernel The MOUNT_PRINT_FILES flags should only be passed when "super_block.s_files" is available. 2/ "mount" is not skipping MNT_CURSOR entries (kernel >= 5.8): crash> mount > mount.out WARNING: cannot get super_block from vfsmnt: 0xff35d65eb1cc1820 crash> struct mount.mnt.mnt_sb,mnt.mnt_flags -x 0xff35d65eb1cc1820 mnt.mnt_sb = 0x0, mnt.mnt_flags = 0x10000000, When crashing with running "findmnt" commands, the mount list will have entries with mnt.mnt_flags==MNT_CURSOR (and mnt.mnt_sb==NULL). Such entries should be skipped without errors. Signed-off-by: Georges Aureau <georges.aureau(a)hpe.com> -- defs.h | 1 + filesys.c | 16 +++++++++++++++- symbols.c | 2 ++ 3 files changed, 18 insertions(+), 1 deletion(-) diff --git a/defs.h b/defs.h index 156ac02..9e37f26 100644 --- a/defs.h +++ b/defs.h @@ -1508,6 +1508,7 @@ struct offset_table { /* stash of commonly-used offsets */ long vfsmount_mnt_devname; long vfsmount_mnt_dirname; long vfsmount_mnt_sb; + long vfsmount_mnt_flags; long vfsmount_mnt_list; long vfsmount_mnt_mountpoint; long vfsmount_mnt_parent; diff --git a/filesys.c b/filesys.c index 8d13807..7439c2e 100644 --- a/filesys.c +++ b/filesys.c @@ -1296,7 +1296,7 @@ cmd_mount(void) * through it for each search argument entered. */ open_tmpfile(); - show_mounts(0, MOUNT_PRINT_FILES | + show_mounts(0, (VALID_MEMBER(super_block_s_files) ? MOUNT_PRINT_FILES : 0) | (VALID_MEMBER(super_block_s_dirty) ? MOUNT_PRINT_INODES : 0), namespace_context); @@ -1371,6 +1371,14 @@ cmd_mount(void) * Do the work for cmd_mount(); */ +/* For kernels >= 5.8, we need to skip MNT_CURSOR entries. + * See https://elixir.bootlin.com/linux/v5.8/source/include/linux/mount.h#L73 + * https://elixir.bootlin.com/linux/v5.8/source/fs/namespace.c#L661 + * https://elixir.bootlin.com/linux/v5.8/source/fs/namespace.c#L690 + * https://elixir.bootlin.com/linux/v5.8/source/fs/proc_namespace.c#L283 + */ +#define MNT_CURSOR 0x10000000 + static void show_mounts(ulong one_vfsmount, int flags, struct task_context *namespace_context) { @@ -1492,6 +1500,11 @@ show_mounts(ulong one_vfsmount, int flags, struct task_context *namespace_contex sbp = ULONG(vfsmount_buf + OFFSET(vfsmount_mnt_sb)); if (!IS_KVADDR(sbp)) { + if (sbp == 0 && VALID_MEMBER(vfsmount_mnt_flags)) { + int mnt_flags = INT(vfsmount_buf + OFFSET(vfsmount_mnt_flags)); + if (mnt_flags == MNT_CURSOR) + continue; + } error(WARNING, "cannot get super_block from vfsmnt: 0x%lx\n", *vfsmnt); continue; } @@ -2070,6 +2083,7 @@ vfs_init(void) MEMBER_OFFSET_INIT(mount_mnt_devname, "mount", "mnt_devname"); MEMBER_OFFSET_INIT(vfsmount_mnt_dirname, "vfsmount", "mnt_dirname"); MEMBER_OFFSET_INIT(vfsmount_mnt_sb, "vfsmount", "mnt_sb"); + MEMBER_OFFSET_INIT(vfsmount_mnt_flags, "vfsmount", "mnt_flags"); MEMBER_OFFSET_INIT(vfsmount_mnt_list, "vfsmount", "mnt_list"); if (INVALID_MEMBER(vfsmount_mnt_devname)) MEMBER_OFFSET_INIT(mount_mnt_list, "mount", "mnt_list"); diff --git a/symbols.c b/symbols.c index 112bcc6..92098a8 100644 --- a/symbols.c +++ b/symbols.c @@ -10685,6 +10685,8 @@ dump_offset_table(char *spec, ulong makestruct) OFFSET(vfsmount_mnt_dirname)); fprintf(fp, " vfsmount_mnt_sb: %ld\n", OFFSET(vfsmount_mnt_sb)); + fprintf(fp, " vfsmount_mnt_flags: %ld\n", + OFFSET(vfsmount_mnt_flags)); fprintf(fp, " vfsmount_mnt_list: %ld\n", OFFSET(vfsmount_mnt_list)); fprintf(fp, " vfsmount_mnt_mountpoint: %ld\n",

1 month, 3 weeks

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1 month, 3 weeks

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[PATCH v2 0/2] extension: Several improvements on eppic extension

by Tao Liu

Eppic works as a crash extension for a long time, and it is a very convenient tool to extend crash's function: 1) People don't need to write an actual crash extension, which requires knowledge of crash APIs, such as readmem(), gdb_interface() etc. Implementing such an crash extension is hard for normal users. 2) Eppic programs are C-syntax-like scripting, no compile needed, so friendly to kernel developers who are already familiar with C. It's a good alternative for people who are unfamiliar with python (comparing to drgn/pykdump). 3) Writing eppic programs is similar to do kernel programming, people can use kernel data structures/global variables directly, again, friendly to kernel developers. Personally I think eppic is a good tool and would like to push it forward to make it used more widely, improved consistently. However I hardly heard anyone who are using it, I guess it is due to it's extension position and unknown to others. In this patchset, I will make several improvements on eppic, although it is still a crash extension, but I think it is made more easily for compile/run/scripting. To-do: Some crash functions should be exposed to eppic, such as maple_tree/rbtree etc, so people can iterate these kernel structures with the existing crash functions, otherwise people need to reimplement those in eppic. A more aggresive improvement of eppic can be found in [1], which people can use call_crash_func() to call any crash's function within eppic script, please refer to code example in [2]. Not sure if people like this, so any feedback/comments are welcomed. v2 -> v1: Removed v1's No.2 & 3 & 5 patch, these 3 are used for compile/preload/alias eppic by default, these are a little aggressive and left to [1] instead. [1]: https://github.com/liutgnu/crash-dev/tree/eppic [2]: https://github.com/liutgnu/crash-dev/blob/eppic/extensions/eppic.patch#L298 Tao Liu (2): extensions: Search all possible paths eppic.patch: Add customized functions to eppic extensions.c | 63 +++++++------ extensions/eppic.mk | 13 ++- extensions/eppic.patch | 210 +++++++++++++++++++++++++++++++++++++++++ 3 files changed, 258 insertions(+), 28 deletions(-) create mode 100644 extensions/eppic.patch -- 2.47.0

1 month, 3 weeks

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1 month, 3 weeks

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[PATCH] Optimize extensions's compiler from gcc to $(CC)

by 高建云

Change the default compiler of the extensions from the fixed gcc to $(CC) passed in by the upper layer Makefile, to facilitate cross_compile. Signed-off-by: jianyun.gao <jianyungao89(a)gmail.com> --- Makefile | 2 +- extensions/Makefile | 10 +++++----- 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/Makefile b/Makefile index b277129..58b1326 100644 --- a/Makefile +++ b/Makefile @@ -727,7 +727,7 @@ extensions: make_configure @$(MAKE) do_extensions do_extensions: - @$(MAKE) -C extensions -i TARGET=$(TARGET) TARGET_CFLAGS="$(CFLAGS) $(TARGET_CFLAGS)" GDB=$(GDB) GDB_FLAGS=$(GDB_FLAGS) + @$(MAKE) -C extensions -i CC=$(CC) TARGET=$(TARGET) TARGET_CFLAGS="$(CFLAGS) $(TARGET_CFLAGS)" GDB=$(GDB) GDB_FLAGS=$(GDB_FLAGS) memory_driver: make_configure @$(MAKE) -C memory_driver -i diff --git a/extensions/Makefile b/extensions/Makefile index e4c68c3..67d3839 100644 --- a/extensions/Makefile +++ b/extensions/Makefile @@ -23,7 +23,7 @@ # suffice, create a .mk file with the same prefix as the .c file, # and that makefile will be invoked. # - +CC ?= gcc CONTRIB_SO := $(patsubst %.c,%.so,$(wildcard *.c)) all: link_defs $(CONTRIB_SO) @@ -37,11 +37,11 @@ $(CONTRIB_SO): %.so: %.c defs.h $(MAKE) -f $*.mk; \ else \ grep -q '((constructor))' $*.c && { \ - echo "gcc -Wall -g -shared -rdynamic -o $@ $*.c -fPIC -D$(TARGET) $(TARGET_CFLAGS) $(GDB_FLAGS)"; \ - gcc -Wall -g -shared -rdynamic -o $@ $*.c -fPIC -D$(TARGET) $(TARGET_CFLAGS) $(GDB_FLAGS); \ + echo "$(CC) -Wall -g -shared -rdynamic -o $@ $*.c -fPIC -D$(TARGET) $(TARGET_CFLAGS) $(GDB_FLAGS)"; \ + $(CC) -Wall -g -shared -rdynamic -o $@ $*.c -fPIC -D$(TARGET) $(TARGET_CFLAGS) $(GDB_FLAGS); \ } || { \ - echo "gcc -Wall -g -nostartfiles -shared -rdynamic -o $@ $*.c -fPIC -D$(TARGET) $(TARGET_CFLAGS) $(GDB_FLAGS)"; \ - gcc -Wall -g -nostartfiles -shared -rdynamic -o $@ $*.c -fPIC -D$(TARGET) $(TARGET_CFLAGS) $(GDB_FLAGS); \ + echo "$(CC) -Wall -g -nostartfiles -shared -rdynamic -o $@ $*.c -fPIC -D$(TARGET) $(TARGET_CFLAGS) $(GDB_FLAGS)"; \ + $(CC) -Wall -g -nostartfiles -shared -rdynamic -o $@ $*.c -fPIC -D$(TARGET) $(TARGET_CFLAGS) $(GDB_FLAGS); \ }; \ fi -- 2.34.1

1 month, 4 weeks

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Patch for Optimize extensions's compilation

by jianyungao89＠gmail.com

1 month, 4 weeks

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Crash-utility September 2025