libctf: serialize: kind suppression and prohibition

The CTF serialization machinery decides whether to write out a dict as BTF
or CTF (or, in LIBCTF_BTM_BTF mode, whether to write out a dict or fail with
ECTF_NOTBTF) in part by looking at the type kinds in the dictionary.

It is possible that you'd like to extend this check and ban specific type
kinds from the dictionary (possibly even if it's CTF); it's also possible
that you'd like to *not* fail even if a CTF-only kind is found, but rather
replace it with a still-valid stub (CTF_K_UNKNOWN / BTF_KIND_UNKNOWN) and
keep going.  (The kernel's btfarchive machinery does this to ensure that
the compiler and previous link stages have emitted only valid BTF type
kinds.)

ctf_write_suppress_kind supports both these use cases:

+int ctf_write_suppress_kind (ctf_dict_t *fp, int kind, int prohibited);

This commit adds only the core population code: the actual suppression is
spread across the serializer and will be added in the next commits.

diff --git a/include/ctf-api.h b/include/ctf-api.h
index 9bbcc04207843ed2bb1776bab253f5a181342c52..a12a9744a7348a91f609e056fdef5fcc10c4492f 100644 (file)
--- a/include/ctf-api.h
+++ b/include/ctf-api.h
@@ -264,6 +264,8 @@ typedef struct ctf_snapshot_id
   _CTF_ITEM (ECTF_NODATASEC, "Variable not found in datasec.") \
   _CTF_ITEM (ECTF_NOTDECLTAG, "This function requires a decl tag.") \
   _CTF_ITEM (ECTF_NOTTAG, "This function requires a type or decl tag.") \
+  _CTF_ITEM (ECTF_KIND_PROHIBITED, "Writeout of suppressed kind attempted.") \
+  _CTF_ITEM (ECTF_NOTBTF, "Cannot write out this dict as BTF.") \
   _CTF_ITEM (ECTF_TOOLARGE, "Prefix required for correct representation.")
 
 #define        ECTF_BASE       1000    /* Base value for libctf errnos.  */
@@ -1106,6 +1108,11 @@ extern int ctf_arc_write (const char *file, ctf_dict_t **ctf_dicts, size_t,
 extern int ctf_arc_write_fd (int, ctf_dict_t **, size_t, const char **,
                             size_t);
 
+/* Prohibit writeout of this type kind: attempts to write it out cause
+   an ECTF_KIND_PROHIBITED error.  */
+
+extern int ctf_write_suppress_kind (ctf_dict_t *fp, int kind, int prohibited);
+
 /* Linking.  These functions are used by ld to link .ctf sections in input
    object files into a single .ctf section which is an archive possibly
    containing members containing types whose names collide across multiple

diff --git a/libctf/ctf-impl.h b/libctf/ctf-impl.h
index 6daed4dea66ffb328940d848e6f70220485d62a1..2e2c558a5be289583ca825a7736be166215df4fe 100644 (file)
--- a/libctf/ctf-impl.h
+++ b/libctf/ctf-impl.h
@@ -389,6 +389,8 @@ struct ctf_dict
   const ctf_dictops_t *ctf_dictops; /* Version-specific dict operations.  */
   ctf_header_t *ctf_header;        /* The header from this CTF dict.  */
   ctf_header_v3_t *ctf_v3_header;   /* The header from an upgraded CTF dict.  */
+  ctf_dynset_t *ctf_write_prohibitions; /* Kinds writeout causes error for.  */
+  ctf_dynset_t *ctf_write_suppressions;        /* Kinds that are skipped on write.  */
   unsigned char ctf_openflags;     /* Flags the dict had when opened.  */
   int ctf_opened_btf;              /* Whether this dict was pure BTF when
                                       opened.  */

diff --git a/libctf/ctf-serialize.c b/libctf/ctf-serialize.c
index ae330e63fb71e20d57833803e1b04e31e034d01b..9b19bcc4ce4c2b6b3a6d2d0126aaf3dee041c08e 100644 (file)
--- a/libctf/ctf-serialize.c
+++ b/libctf/ctf-serialize.c
@@ -762,6 +762,39 @@ symerr:
 
 /* Type section.  */
 
+/* Kind suppression.  */
+
+int
+ctf_write_suppress_kind (ctf_dict_t *fp, int kind, int prohibited)
+{
+  ctf_dynset_t *set;
+
+  if (kind < CTF_K_UNKNOWN || kind > CTF_K_MAX)
+    return (ctf_set_errno (fp, EINVAL));
+
+  if (prohibited)
+    set = fp->ctf_write_prohibitions;
+  else
+    set = fp->ctf_write_suppressions;
+
+  if (!set)
+    {
+      set = ctf_dynset_create (htab_hash_pointer, htab_eq_pointer, NULL);
+      if (!set)
+       return (ctf_set_errno (fp, errno));
+
+      if (prohibited)
+       fp->ctf_write_prohibitions = set;
+      else
+       fp->ctf_write_suppressions = set;
+    }
+
+  if ((ctf_dynset_cinsert (set, (const void *) (uintptr_t) kind)) < 0)
+    return (ctf_set_errno (fp, errno));
+
+  return 0;
+}
+
 /* Iterate through the static types and the dynamic type definition list and
    compute the size of the CTF type section.
 

diff --git a/libctf/libctf.ver b/libctf/libctf.ver
index 8aa9f356db76e871c20fb0c524660fad3e435394..3ad5176a14188e7613c4d7c67769781c254a8675 100644 (file)
--- a/libctf/libctf.ver
+++ b/libctf/libctf.ver
@@ -167,6 +167,7 @@ LIBCTF_2.0 {
        ctf_write_mem;
        ctf_gzwrite;
        ctf_compress_write;
+       ctf_write_suppress_kind;
        ctf_sect_size;
        ctf_getdatasect;
        ctf_getsymsect;