The 04/20/2021 13:44, Firo Yang wrote:
Hi Kazu-san,
> This new O option is very useful to specify the head node
> offset for listing linked list whose head node embedded has a
> different offset to other node, e.g. dentry.d_subdirs(the head node)
> and dentry.d_child.
>
> Signed-off-by: Firo Yang <firo.yang@xxxxxxxx>
> ---
> defs.h | 1 +
> help.c | 12 +++++++++++-
> tools.c | 30 +++++++++++++++++++++++++++---
> 3 files changed, 39 insertions(+), 4 deletions(-)
>
> diff --git a/defs.h b/defs.h
> index 35b983a..764facf 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -2605,6 +2605,7 @@ struct list_data { /* generic structure used by do_list() to walk */
> #define LIST_PARSE_MEMBER (VERBOSE << 13)
> #define LIST_READ_MEMBER (VERBOSE << 14)
> #define LIST_BRENT_ALGO (VERBOSE << 15)
> +#define LIST_HEAD_OFFSET_ENTERED (VERBOSE << 16)
>
> struct tree_data {
> ulong flags;
> diff --git a/help.c b/help.c
> index 531f50a..b561f3b 100644
> --- a/help.c
> +++ b/help.c
> @@ -5716,7 +5716,7 @@ char *help__list[] = {
> "list",
> "linked list",
> "[[-o] offset][-e end][-[s|S] struct[.member[,member] [-l offset]] -[x|d]]"
> -"\n [-r|-B] [-h|-H] start",
> +"\n [-r|-B] [-h [-O head_offset]|-H] start",
> " ",
> " This command dumps the contents of a linked list. The entries in a linked",
> " list are typically data structures that are tied together in one of two",
> @@ -5800,6 +5800,16 @@ char *help__list[] = {
> " -S struct Similar to -s, but instead of parsing gdb output, member values",
> " are read directly from memory, so the command works much faster",
> " for 1-, 2-, 4-, and 8-byte members.",
> +" -O offset The -O option works only with -h option.",
> +" It is used for specifying the offset of head node embedded in a",
> +" structure, like dentry.d_subdirs or cgroup_subsys_state.children.",
> +" The offset may be entered in either of two manners:",
> +"",
> +" 1. \"structure.member\" format.",
> +" 2. a number of bytes.",
> +"",
> +" You can use it like the following:",
> +" list -O <head node offset> -o <node offset> -h start -s <...>",
> " -l offset Only used in conjunction with -s, if the start address argument",
> " is a pointer to an embedded list head (or any other similar list",
> " linkage structure whose first member points to the next linkage",
> diff --git a/tools.c b/tools.c
> index a26b101..792a567 100644
> --- a/tools.c
> +++ b/tools.c
> @@ -3343,6 +3343,7 @@ void
> cmd_list(void)
> {
> int c;
> + long head_member_offset; /* offset for head like denty.d_subdirs */
> struct list_data list_data, *ld;
> struct datatype_member struct_member, *sm;
> struct syment *sp;
> @@ -3353,7 +3354,7 @@ cmd_list(void)
> BZERO(ld, sizeof(struct list_data));
> struct_list_offset = 0;
>
> - while ((c = getopt(argcnt, args, "BHhrs:S:e:o:xdl:")) != EOF) {
> + while ((c = getopt(argcnt, args, "BHhrs:S:e:o:O:xdl:")) != EOF) {
> switch(c)
> {
> case 'B':
> @@ -3394,6 +3395,24 @@ cmd_list(void)
> optarg);
> break;
>
> + case 'O':
> + if (ld->flags & LIST_HEAD_OFFSET_ENTERED)
> + error(FATAL,
> + "offset value %d (0x%lx) already entered\n",
> + head_member_offset, head_member_offset);
> + else if (IS_A_NUMBER(optarg))
> + head_member_offset = stol(optarg,
> + FAULT_ON_ERROR, NULL);
> + else if (arg_to_datatype(optarg,
> + sm, RETURN_ON_ERROR) > 1)
> + head_member_offset = sm->member_offset;
> + else
> + error(FATAL, "invalid -O argument: %s\n",
> + optarg);
> +
> + ld->flags |= LIST_HEAD_OFFSET_ENTERED;
> + break;
> +
> case 'o':
> if (ld->flags & LIST_OFFSET_ENTERED)
> error(FATAL,
> @@ -3599,8 +3618,13 @@ next_arg:
> fprintf(fp, "(empty)\n");
> return;
> }
> - } else
> - ld->start += ld->list_head_offset;
> + } else {
> + if (ld->flags & LIST_HEAD_OFFSET_ENTERED)
> + readmem(ld->start + head_member_offset, KVADDR,
> + &ld->start, sizeof(void *), "LIST_HEAD contents", FAULT_ON_ERROR);
> + else
> + ld->start += ld->list_head_offset;
> + }
> }
>
> ld->flags &= ~(LIST_OFFSET_ENTERED|LIST_START_ENTERED);
> --
> 2.30.2
>
I am not sure whether this patch is considered helpful or not.
Could you please share some thoughts?
Thanks,
Firo
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