[Crash-utility] [PATCH v3 1/1] tools: list: create O option for specifying head node offset (Firo Yang)
Firo Yang
firo.yang at suse.com
Wed Jun 16 07:24:17 UTC 2021
The 06/01/2021 13:01, lijiang wrote:
> Hi, Firo
> Thank you for the update.
> On Wed, May 26, 2021 at 12:00 AM <crash-utility-request at redhat.com> wrote:
>
> > Date: Tue, 25 May 2021 18:17:37 +0800
> > From: Firo Yang <firo.yang at suse.com>
> > To: k-hagio-ab at nec.com
> > Cc: firogm at gmail.com, crash-utility at redhat.com
> > Subject: [Crash-utility] [PATCH v3 1/1] tools: list: create O option
> > for specifying head node offset
> > Message-ID: <20210525101737.51232-1-firo.yang at suse.com>
> > Content-Type: text/plain
> >
> > This -O option is very useful to specify the embedded head node's
> > offset which is different to the offset of other nodes embedded,
> > e.g. dentry.d_subdirs(the head node) and dentry.d_child.
> >
> > Signed-off-by: Firo Yang <firo.yang at suse.com>
> > ---
> > defs.h | 1 +
> > help.c | 32 +++++++++++++++++++++++++++++++-
> > tools.c | 36 +++++++++++++++++++++++++++++++++---
> > 3 files changed, 65 insertions(+), 4 deletions(-)
> >
> > diff --git a/defs.h b/defs.h
> > index 396d61a..d5fcd37 100644
> > --- a/defs.h
> > +++ b/defs.h
> > @@ -2613,6 +2613,7 @@ 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 e0c8408..1593f12 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 +5800,15 @@ 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 Only used in conjunction with -h; it specifies the offset
> > of head",
> > +" node list_head embedded within a data structure which is
> > different",
> > +" than the offset of list_head of other nodes embedded
> > within a data",
> > +" structure.",
> > +" The offset may be entered in either of the following
> > manners:",
> > +"",
> > +" 1. \"structure.member\" format.",
> > +" 2. a number of bytes.",
> > +"",
> > " -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",
> > @@ -6116,6 +6125,27 @@ char *help__list[] = {
> > " comm = \"sudo\"",
> > " ffff88005ac10180",
> > " comm = \"crash\"",
> > +"",
> > +" To display a liked list whose head node and other nodes are embedded
> > within ",
> > +" either same or different data structures resulting in different
> > offsets ",
> > +" for head node and other nodes, e.g. dentry.d_subdirs and
> > dentry.d_child, this",
> > +" -O option can be used:",
> > +"",
> > +" %s> list -o dentry.d_child -s dentry.d_name.name -O
> > dentry.d_subdirs -h ffff9c585b81a180",
> > +" ffff9c585b9cb140",
> > +" d_name.name = 0xffff9c585b9cb178 ccc.txt",
> > +" ffff9c585b9cb980",
> > +" d_name.name = 0xffff9c585b9cb9b8 bbb.txt",
> > +" ffff9c585b9cb740",
> > +" d_name.name = 0xffff9c585b9cb778 aaa.txt",
> > +"",
> > +" The dentry.d_subdirs example above is equal to the following
> > sequence:",
> > +"",
> > +" %s> struct -o dentry.d_subdirs ffff9c585b81a180",
> > +" struct dentry {",
> > +" [ffff9c585b81a220] struct list_head d_subdirs;",
> > +" }",
> > +" %s> list -o dentry.d_child -s dentry.d_name.name -H
> > ffff9c585b81a220",
> > NULL
> > };
> >
> > diff --git a/tools.c b/tools.c
> > index a26b101..636adc6 100644
> > --- a/tools.c
> > +++ b/tools.c
> > @@ -3343,6 +3343,7 @@ void
> > cmd_list(void)
> > {
> > int c;
> > + long head_member_offset = 0; /* 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 +3618,19 @@ next_arg:
> > fprintf(fp, "(empty)\n");
> > return;
> > }
> > - } else
> > - ld->start += ld->list_head_offset;
> > + } else {
> > + if (ld->flags & LIST_HEAD_OFFSET_ENTERED) {
> > + if (!ld->end)
> > + ld->end = ld->start +
> > head_member_offset;
> > + readmem(ld->start + head_member_offset,
> > KVADDR,
> > + &ld->start, sizeof(void *),
> > "LIST_HEAD contents", FAULT_ON_ERROR);
> > + if (ld->start == ld->end) {
> > + fprintf(fp, "(empty)\n");
> > + return;
> > + }
> >
>
> The code block " if (ld->flags & LIST_HEAD_OFFSET_ENTERED) " should be at
> the same level with the code block "if (ld->flags & LIST_OFFSET_ENTERED)",
> just like the option "-o" and "-O" in the "switch-case" code blocks. For
> example:
>
> if (ld->flags & LIST_HEAD_POINTER) {
> if (!ld->end)
> ld->end = ld->start;
> readmem(ld->start + ld->member_offset, KVADDR,
> &ld->start,
> sizeof(void *), "LIST_HEAD contents",
> FAULT_ON_ERROR);
> if (ld->start == ld->end) {
> fprintf(fp, "(empty)\n");
> return;
> }
> + } else if (ld->flags & LIST_HEAD_OFFSET_ENTERED) {
> + if (!ld->end)
> + ld->end = ld->start + head_member_offset;
> + readmem(ld->start + head_member_offset, KVADDR,
> + &ld->start, sizeof(void *), "LIST_HEAD
> contents", FAULT_ON_ERROR);
> + if (ld->start == ld->end) {
> + fprintf(fp, "(empty)\n");
> + return;
> + }
> } else
> ld->start += ld->list_head_offset;
>
> The code looks more readable, but the above two "if" code blocks look very
> similar, not sure if the code refactoring will be needed.
>
> What do you think about this? Firo and Kazu.
Hi Lianbo, after thinking about this code for a while, I think the code
refactoring is not necessary because
1) the original code makes more sense to express the mutual exclusive
semantics between -H (ld->flags & LIST_HEAD_POINTER) and -h.
2) LIST_HEAD_OFFSET_ENTERED and LIST_OFFSET_ENTERED don't have to
be at same level because LIST_HEAD_OFFSET_ENTERED is just a sub-option for -h.
So please consider accepting the original patch.
Thanks,
Firo
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