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libctf: lookup_by_name: do not return success for nonexistent pointer types

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The recent work allowing lookups of pointers in child dicts when the
pointed-to type is in the parent dict broke the case where a pointer
type that does not exist at all is looked up: we mistakenly return the
pointed-to type, which is likely not a pointer at all.  This causes
considerable confusion.

Fixed, with a new testcase.

libctf/ChangeLog
2021-01-19  Nick Alcock  <nick.alcock@oracle.com>

	* ctf-lookup.c (ctf_lookup_by_name_internal): Do not return the
	base type if looking up a nonexistent pointer type.
	* testsuite/libctf-regression/pptrtab*: Test it.
This commit is contained in:
Nick Alcock 2021-01-19 12:45:18 +00:00
parent c98de297b3
commit e05a3e5a49
5 changed files with 45 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
libctf/ChangeLog
View File

@ -1,3 +1,9 @@
2021-01-19 Nick Alcock <nick.alcock@oracle.com>
* ctf-lookup.c (ctf_lookup_by_name_internal): Do not return the
base type if looking up a nonexistent pointer type.
* testsuite/libctf-regression/pptrtab*: Test it.
2021-01-13 Alan Modra <amodra@gmail.com>
* Makefile.in: Regenerate.

34
libctf/ctf-lookup.c
View File

@ -184,24 +184,36 @@ ctf_lookup_by_name_internal (ctf_dict_t *fp, ctf_dict_t *child,
from resolving the type down to its base type and use that instead.
This helps with cases where the CTF data includes "struct foo *"
but not "foo_t *" and the user tries to access "foo_t *" in the
debugger. */
debugger.
There is extra complexity here because uninitialized elements in
the pptrtab and ptrtab are set to zero, but zero (as the type ID
meaning the unimplemented type) is a valid return type from
ctf_lookup_by_name. (Pointers to types are never of type 0, so
this is unambiguous, just fiddly to deal with.) */
uint32_t idx = LCTF_TYPE_TO_INDEX (fp, type);
int in_child = 0;
ntype = type;
ntype = CTF_ERR;
if (child && idx <= child->ctf_pptrtab_len)
{
ntype = child->ctf_pptrtab[idx];
if (ntype)
in_child = 1;
else
ntype = CTF_ERR;
}
if (ntype == 0)
ntype = fp->ctf_ptrtab[idx];
if (ntype == CTF_ERR)
{
ntype = fp->ctf_ptrtab[idx];
if (ntype == 0)
ntype = CTF_ERR;
}
/* Try resolving to its base type and check again. */
if (ntype == 0)
if (ntype == CTF_ERR)
{
if (child)
ntype = ctf_type_resolve_unsliced (child, type);
@ -213,16 +225,22 @@ ctf_lookup_by_name_internal (ctf_dict_t *fp, ctf_dict_t *child,
idx = LCTF_TYPE_TO_INDEX (fp, ntype);
ntype = 0;
ntype = CTF_ERR;
if (child && idx <= child->ctf_pptrtab_len)
{
ntype = child->ctf_pptrtab[idx];
if (ntype)
in_child = 1;
else
ntype = CTF_ERR;
}
if (ntype == 0)
ntype = fp->ctf_ptrtab[idx];
if (ntype == CTF_ERR)
{
ntype = fp->ctf_ptrtab[idx];
if (ntype == 0)
ntype = CTF_ERR;
}
if (ntype == CTF_ERR)
goto notype;
}

2
libctf/testsuite/libctf-regression/pptrtab-a.c
View File

@ -1,3 +1,5 @@
typedef long a_t;
typedef long b_t;
a_t *a;
b_t ignore2;

3
libctf/testsuite/libctf-regression/pptrtab-b.c
View File

@ -1,4 +1,5 @@
typedef long a_t;
typedef long b_t;
a_t b;
b_t ignore1;

10
libctf/testsuite/libctf-regression/pptrtab.c
View File

@ -23,13 +23,18 @@ main (int argc, char *argv[])
goto open_err;
/* Make sure we can look up a_t * by name in all non-parent dicts, even though
the a_t * and the type it points to are in distinct dicts. */
the a_t * and the type it points to are in distinct dicts; make sure we
cannot look up b_t *. */
while ((fp = ctf_archive_next (ctf, &i, &arcname, 1, &err)) != NULL)
{
if ((type = ctf_lookup_by_name (fp, "a_t *")) == CTF_ERR)
goto err;
if ((ctf_lookup_by_name (fp, "b_t *")) != CTF_ERR ||
ctf_errno (fp) != ECTF_NOTYPE)
goto noerr;
if (ctf_type_reference (fp, type) == CTF_ERR)
goto err;
@ -51,4 +56,7 @@ main (int argc, char *argv[])
err:
fprintf (stderr, "Lookup failed in %s: %s\n", arcname, ctf_errmsg (ctf_errno (fp)));
return 1;
noerr:
fprintf (stderr, "Lookup unexpectedly succeeded in %s\n", arcname);
return 1;
}