[PATCH 1/1] libctf: introduce ctf_func_type_{info,args}, ctf_type_aname_raw

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[PATCH 1/1] libctf: introduce ctf_func_type_{info,args}, ctf_type_aname_raw

Nick Alcock
The first two of these allow you to get function type info and args out
of the types section give a type ID: astonishingly, this was missing
from libctf before now: so even though types of kind CTF_K_FUNCTION were
supported, you couldn't find out anything about them.  (The existing
ctf_func_info and ctf_func_args only allow you to get info about
functions in the function section, i.e. given symbol table indexes, not
type IDs.)

The second of these allows you to get the raw undecorated name out of
the CTF section (strdupped for safety) without traversing subtypes to
build a full C identifier out of it.  It's useful for things that are
already tracking the type kind etc and just need an unadorned name.

include/
        * ctf-api.h (ECTF_NOTFUNC): Fix description.
        (ctf_func_type_info): New.
        (ctf_func_type_args): Likewise.
libctf/
        * ctf-types.c (ctf_type_aname_raw): New.
        (ctf_func_type_info): Likewise.
        (ctf_func_type_args): Likewise.
        * ctf-error.c (_ctf_errlist): Fix description.
---
 include/ctf-api.h   |  5 ++-
 libctf/ctf-error.c  |  2 +-
 libctf/ctf-lookup.c |  2 +-
 libctf/ctf-types.c  | 85 +++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 91 insertions(+), 3 deletions(-)

diff --git a/include/ctf-api.h b/include/ctf-api.h
index 3acbc91b9a..1a0d47eae1 100644
--- a/include/ctf-api.h
+++ b/include/ctf-api.h
@@ -160,7 +160,7 @@ enum
    ECTF_NAMELEN, /* Buffer is too small to hold type name.  */
    ECTF_NOTYPE, /* No type found corresponding to name.  */
    ECTF_SYNTAX, /* Syntax error in type name.  */
-   ECTF_NOTFUNC, /* Symtab entry does not refer to a function.  */
+   ECTF_NOTFUNC, /* Symbol entry or type is not a function.  */
    ECTF_NOFUNCDAT, /* No func info available for function.  */
    ECTF_NOTDATA, /* Symtab entry does not refer to a data obj.  */
    ECTF_NOTYPEDAT, /* No type info available for object.  */
@@ -277,6 +277,8 @@ extern int ctf_version (int);
 
 extern int ctf_func_info (ctf_file_t *, unsigned long, ctf_funcinfo_t *);
 extern int ctf_func_args (ctf_file_t *, unsigned long, uint32_t, ctf_id_t *);
+extern int ctf_func_type_info (ctf_file_t *, ctf_id_t, ctf_funcinfo_t *);
+extern int ctf_func_type_args (ctf_file_t *, ctf_id_t, uint32_t, ctf_id_t *);
 
 extern ctf_id_t ctf_lookup_by_name (ctf_file_t *, const char *);
 extern ctf_id_t ctf_lookup_by_symbol (ctf_file_t *, unsigned long);
@@ -284,6 +286,7 @@ extern ctf_id_t ctf_lookup_variable (ctf_file_t *, const char *);
 
 extern ctf_id_t ctf_type_resolve (ctf_file_t *, ctf_id_t);
 extern char *ctf_type_aname (ctf_file_t *, ctf_id_t);
+extern char *ctf_type_aname_raw (ctf_file_t *, ctf_id_t);
 extern ssize_t ctf_type_lname (ctf_file_t *, ctf_id_t, char *, size_t);
 extern char *ctf_type_name (ctf_file_t *, ctf_id_t, char *, size_t);
 extern ssize_t ctf_type_size (ctf_file_t *, ctf_id_t);
diff --git a/libctf/ctf-error.c b/libctf/ctf-error.c
index af3a6c7fd2..660a30aa64 100644
--- a/libctf/ctf-error.c
+++ b/libctf/ctf-error.c
@@ -48,7 +48,7 @@ static const char *const _ctf_errlist[] = {
   "Input buffer is too small for type name",     /* ECTF_NAMELEN */
   "No type information available for that name",     /* ECTF_NOTYPE */
   "Syntax error in type name",     /* ECTF_SYNTAX */
-  "Symbol table entry is not a function",     /* ECTF_NOTFUNC */
+  "Symbol table entry or type is not a function",    /* ECTF_NOTFUNC */
   "No function information available for symbol",    /* ECTF_NOFUNCDAT */
   "Symbol table entry is not a data object",     /* ECTF_NOTDATA */
   "No type information available for symbol",     /* ECTF_NOTYPEDAT */
diff --git a/libctf/ctf-lookup.c b/libctf/ctf-lookup.c
index 4089ad9ffa..40eaf9c819 100644
--- a/libctf/ctf-lookup.c
+++ b/libctf/ctf-lookup.c
@@ -1,4 +1,4 @@
-/* Type lookup.
+/* Symbol, variable and name lookup.
    Copyright (C) 2019 Free Software Foundation, Inc.
 
    This file is part of libctf.
diff --git a/libctf/ctf-types.c b/libctf/ctf-types.c
index dc158e2f52..5068ff16a5 100644
--- a/libctf/ctf-types.c
+++ b/libctf/ctf-types.c
@@ -369,6 +369,23 @@ ctf_type_name (ctf_file_t *fp, ctf_id_t type, char *buf, size_t len)
   return (rv >= 0 && (size_t) rv < len ? buf : NULL);
 }
 
+/* Lookup the given type ID and return its raw, unadorned, undecorated name as a
+   new dynamcally-allocated string.  */
+
+char *
+ctf_type_aname_raw (ctf_file_t *fp, ctf_id_t type)
+{
+  const ctf_type_t *tp;
+
+  if ((tp = ctf_lookup_by_id (&fp, type)) == NULL)
+    return NULL; /* errno is set for us.  */
+
+  if (ctf_strraw (fp, tp->ctt_name) != NULL)
+    return strdup (ctf_strraw (fp, tp->ctt_name));
+
+  return NULL;
+}
+
 /* Resolve the type down to a base type node, and then return the size
    of the type storage in bytes.  */
 
@@ -948,6 +965,74 @@ ctf_enum_value (ctf_file_t * fp, ctf_id_t type, const char *name, int *valp)
   return -1;
 }
 
+/* Given a type ID relating to a function type, return info on return types and
+   arg counts for that function.  */
+
+int
+ctf_func_type_info (ctf_file_t *fp, ctf_id_t type, ctf_funcinfo_t *fip)
+{
+  const ctf_type_t *tp;
+  uint32_t kind;
+  const uint32_t *args;
+  ssize_t size, increment;
+
+  if ((type = ctf_type_resolve (fp, type)) == CTF_ERR)
+    return -1; /* errno is set for us.  */
+
+  if ((tp = ctf_lookup_by_id (&fp, type)) == NULL)
+    return -1; /* errno is set for us.  */
+
+  (void) ctf_get_ctt_size (fp, tp, &size, &increment);
+  kind = LCTF_INFO_KIND (fp, tp->ctt_info);
+
+  if (kind != CTF_K_FUNCTION)
+    return (ctf_set_errno (fp, ECTF_NOTFUNC));
+
+  fip->ctc_return = tp->ctt_type;
+  fip->ctc_argc = LCTF_INFO_VLEN (fp, tp->ctt_info);
+  fip->ctc_flags = 0;
+
+  args = (uint32_t *) ((uintptr_t) tp + increment);
+
+  if (fip->ctc_argc != 0 && args[fip->ctc_argc - 1] == 0)
+    {
+      fip->ctc_flags |= CTF_FUNC_VARARG;
+      fip->ctc_argc--;
+    }
+
+  return 0;
+}
+
+/* Given a type ID relating to a function type,, return the arguments for the
+   function.  */
+
+int
+ctf_func_type_args (ctf_file_t *fp, ctf_id_t type, uint32_t argc, ctf_id_t *argv)
+{
+  const ctf_type_t *tp;
+  const uint32_t *args;
+  ssize_t size, increment;
+  ctf_funcinfo_t f;
+
+  if (ctf_func_type_info (fp, type, &f) < 0)
+    return -1; /* errno is set for us.  */
+
+  if ((type = ctf_type_resolve (fp, type)) == CTF_ERR)
+    return -1; /* errno is set for us.  */
+
+  if ((tp = ctf_lookup_by_id (&fp, type)) == NULL)
+    return -1; /* errno is set for us.  */
+
+  (void) ctf_get_ctt_size (fp, tp, &size, &increment);
+
+  args = (uint32_t *) ((uintptr_t) tp + increment);
+
+  for (argc = MIN (argc, f.ctc_argc); argc != 0; argc--)
+    *argv++ = *args++;
+
+  return 0;
+}
+
 /* Recursively visit the members of any type.  This function is used as the
    engine for ctf_type_visit, below.  We resolve the input type, recursively
    invoke ourself for each type member if the type is a struct or union, and
--
2.22.0.238.g049a27acdc

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Re: [PATCH 1/1] libctf: introduce ctf_func_type_{info,args}, ctf_type_aname_raw

Nick Alcock
(This precedes the ld series, which I will rebase atop it, because I
expect it to take longer to review the ld series than this one patch.)

On 18 Jul 2019, Nick Alcock spake thusly:

> The first two of these allow you to get function type info and args out
> of the types section give a type ID: astonishingly, this was missing
> from libctf before now: so even though types of kind CTF_K_FUNCTION were
> supported, you couldn't find out anything about them.  (The existing
> ctf_func_info and ctf_func_args only allow you to get info about
> functions in the function section, i.e. given symbol table indexes, not
> type IDs.)
[...]
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Re: [PATCH 1/1] libctf: introduce ctf_func_type_{info,args}, ctf_type_aname_raw

Nick Alcock
On 18 Jul 2019, Nick Alcock verbalised:

> (This precedes the ld series, which I will rebase atop it, because I
> expect it to take longer to review the ld series than this one patch.)

(This has been pushed.)