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libctf: fix querying of large structures

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After GCC PR 121411 is fixed, large structures (with offsets > 512MiB)
are written correctly... but libctf cannot query them properly unless
they are even bigger (> 4GiB), because it checks to see if the ctt_size
is CTF_LSIZE_SENT to decide whether to use a ctf_lmember_t or a
ctf_member_t to encode the structure members.  But the structure member
offsets are in *bits*, not bytes: the right value to check is
CTF_LSTRUCT_THRESH, which is 1/8th the size.

(Thanks to Martin Pirker <martin.pirker1@chello.at> for the diagnosis
and fix.)

Testing this is a bit fun, because we don't want to emit an error if the
compiler is broken: but we cannot tell whether the compiler is broken
using the existing lookup harness, because its input is passed through
the linker (and thus the broken ld).  So add another sort of link mode,
"objects", which keeps the constituent object files around and passes
both the final linker output and the object files that make it up to the
lookup program.  Our testcase can then check the linker input to see if
the compiler is buggy, and only if it isn't check the linker output and
fail if things aren't right.

libctf/
	PR libctf/33339
	* ctf-types.c (ctf_struct_member): Check CTF_LSTRUCT_THRESH, not
	CTF_LSIZE_SENT.
	* testsuite/lib/ctf-lib.exp (run_lookup_test): New 'objects'
	link option.
	* testsuite/libctf-lookup/big-struct-corruption.*: New test.
	* testsuite/libctf-lookup/big-struct-ctf.c: New test input.
This commit is contained in:
Nick Alcock
2025-09-22 21:07:11 +01:00
parent 6fb5a51c40
commit 7412b0a35c
5 changed files with 228 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
libctf/ctf-types.c
View File

@@ -45,7 +45,7 @@ ctf_struct_member (ctf_dict_t *fp, ctf_lmember_t *dst, const ctf_type_t *tp,
return -1; /* errno is set for us. */
/* Already large. */
if (tp->ctt_size == CTF_LSIZE_SENT)
if (tp->ctt_size >= CTF_LSTRUCT_THRESH)
{
ctf_lmember_t *lmp = (ctf_lmember_t *) vlen;

43
libctf/testsuite/lib/ctf-lib.exp
View File

@@ -141,6 +141,8 @@ proc compile_link_one_host_cc { src output additional_args } {
#
# link:
# If set, link the SOURCE together even if only one file is specified.
# If "objects", keep the input object files and pass them as additional
# arguments to LOOKUP.
#
# link_flags:
# If set, extra flags to pass to the linker.
@@ -265,11 +267,14 @@ proc run_lookup_test { name } {
# Compile the inputs and posibly link them together.
set lookup_output ""
set objs {}
if { [llength $opts(source)] > 0 } {
set lookup_flags ""
set ld_flags ""
if { $run_ld } {
set lookup_output "tmpdir/out.so"
set lookup_flags "-gctf -fPIC $shared $opts(link_flags)"
set lookup_flags "-gctf -fPIC"
set ld_flags "$shared $opts(link_flags)"
} else {
set lookup_output "tmpdir/out.o"
set lookup_flags "-gctf -fPIC -c"
@@ -280,19 +285,38 @@ proc run_lookup_test { name } {
if [board_info [target_info name] exists ldflags] {
append lookup_flags " [board_info [target_info name] ldflags]"
}
set src {}
set objsrcs {}
set local_srcs {}
foreach sfile $opts(source) {
set local_src [file join [file dirname $file] $sfile]
lappend local_srcs $local_src
if [is_remote host] {
lappend src [remote_download host [file join [file dirname $file] $sfile]]
set src [remote_download host [file join [file dirname $file] $sfile]]
} else {
lappend src [file join [file dirname $file] $sfile]
set src [file join [file dirname $file] $sfile]
}
if { $opts(link) == "objects" } {
set obj "[file rootname $src].o"
set comp_output [prune_warnings [run_host_cmd "$CC_FOR_TARGET" "$CFLAGS_FOR_TARGET $lookup_flags $src -c -o $obj"]]
if { $comp_output != ""} {
send_log "compilation of CTF program $local_src failed with <$comp_output>"
fail $testname
return 0
}
lappend objsrcs $obj
lappend objs $obj
} else {
lappend objsrcs $src
}
}
set comp_output [prune_warnings [run_host_cmd "$CC_FOR_TARGET" "$CFLAGS_FOR_TARGET $lookup_flags [concat $src] -o $lookup_output"]]
set comp_output [prune_warnings [run_host_cmd "$CC_FOR_TARGET" "$CFLAGS_FOR_TARGET $lookup_flags $ld_flags [concat $objsrcs] -o $lookup_output"]]
if { $comp_output != ""} {
send_log "compilation of CTF program [concat $src] failed with <$comp_output>"
send_log "compilation of CTF program [concat $local_srcs] failed with <$comp_output>"
fail $testname
return 0
}
@@ -306,12 +330,13 @@ proc run_lookup_test { name } {
}
}
# Invoke the lookup program on the outputs, possibly through the wrapper.
# Invoke the lookup program on the outputs, possibly through the wrapper, including all
# the object file names if they were filled out.
if { [llength $opts(wrapper)] == 0 } {
set results [run_host_cmd tmpdir/lookup $lookup_output]
set results [run_host_cmd tmpdir/lookup "$lookup_output $objs"]
} else {
set results [run_host_cmd "$opts(wrapper) tmpdir/lookup" $lookup_output]
set results [run_host_cmd "$opts(wrapper) tmpdir/lookup" "$lookup_output $objs"]
}
if { [regexp {^UNSUPPORTED: (.*)$} $results -> reason] } {

118
libctf/testsuite/libctf-lookup/big-struct-corruption.c Normal file
View File

@@ -0,0 +1,118 @@
/* Determine whether libctf/33339 is fixed, if and only if GCC PR 121411 is also
fixed. */
#include "config.h"
#include <ctf-api.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/* Determine whether the passed-in struct's member's offsets ever descend. */
static int
offsets_ascending (ctf_dict_t *fp, ctf_id_t type)
{
ctf_next_t *it = NULL;
ssize_t offset, last_offset = 0;
while ((offset = ctf_member_next (fp, type, &it, NULL, NULL, 0)) >= 0)
{
if (offset < last_offset)
return 0;
last_offset = offset;
}
if (ctf_errno (fp) != ECTF_NEXT_END)
{
fprintf (stderr, "Cannot check member offsets: %s\n",
ctf_errmsg (ctf_errno (fp)));
exit (0);
}
return 1;
}
int
main (int argc, char *argv[])
{
ctf_archive_t *ctf;
ctf_dict_t *fp;
ctf_id_t type;
int err;
if (argc != 3)
{
fprintf (stderr, "Syntax: %s PROGRAM OBJ\n", argv[0]);
exit(1);
}
/* Check for bugginess of compiler. */
if ((ctf = ctf_open (argv[2], NULL, &err)) == NULL)
{
fprintf (stderr, "Cannot open compiler object file %s: %s\n",
argv[2], ctf_errmsg (err));
exit (1);
}
/* Verify that offsets only ascend. */
if ((fp = ctf_arc_lookup_symbol_name (ctf, "huge_used", &type, &err)) == NULL)
{
fprintf (stderr, "UNSUPPORTED: compiler does not provide expected symbol.\n");
exit (0);
}
if (!offsets_ascending (fp, type))
{
fprintf (stderr, "UNSUPPORTED: GCC bug PR121411 detected.\n");
exit (0);
}
ctf_dict_close (fp);
ctf_close (ctf);
/* Check if test is disabled (e.g. on 32-bit). */
if ((ctf = ctf_open (argv[1], NULL, &err)) == NULL)
{
fprintf (stderr, "Cannot open linked binary test file %s: %s\n",
argv[1], ctf_errmsg (err));
exit (1);
}
if ((fp = ctf_arc_lookup_symbol_name (ctf, "test_disabled", &type, &err)) != NULL)
{
fprintf (stderr, "UNSUPPORTED: test not necessary on 32-bit targets.\n");
exit (0);
}
if ((fp = ctf_arc_lookup_symbol_name (ctf, "big_used", &type, &err)) == NULL)
{
fprintf (stderr, "big struct symbol not found.\n");
exit (1);
}
if (!offsets_ascending (fp, type))
{
fprintf (stderr, "large struct offsets incorrect.\n");
exit (1);
}
ctf_dict_close (fp);
if ((fp = ctf_arc_lookup_symbol_name (ctf, "huge_used", &type, &err)) == NULL)
{
fprintf (stderr, "huge struct symbol not found.\n");
exit (1);
}
if (!offsets_ascending (fp, type))
{
fprintf (stderr, "huge struct offsets incorrect.\n");
exit (1);
}
ctf_dict_close (fp);
ctf_close (ctf);
fprintf (stderr, "Large and huge structs working fine.\n");
exit (0);
}

3
libctf/testsuite/libctf-lookup/big-struct-corruption.lk Normal file
View File

@@ -0,0 +1,3 @@
# source: big-struct-ctf.c
# link: objects
Large and huge structs working fine.

72
libctf/testsuite/libctf-lookup/big-struct-ctf.c Normal file
View File

@@ -0,0 +1,72 @@
#if defined (__SIZEOF_PTRDIFF_T__) && __SIZEOF_PTRDIFF_T__ > 4
#define CONCAT_(a,b) a ## b
#define CONCAT(a,b) CONCAT_(a, b)
#define COUNT(name) CONCAT(name, __COUNTER__)
#define MEMBNAME const char COUNT(memb)[1024 * 1024]
#define MEMB10 \
MEMBNAME; \
MEMBNAME; \
MEMBNAME; \
MEMBNAME; \
MEMBNAME; \
MEMBNAME; \
MEMBNAME; \
MEMBNAME; \
MEMBNAME; \
MEMBNAME;
#define MEMB100 \
MEMB10 \
MEMB10 \
MEMB10 \
MEMB10 \
MEMB10 \
MEMB10 \
MEMB10 \
MEMB10 \
MEMB10 \
MEMB10
#define MEMB1000 \
MEMB100 \
MEMB100 \
MEMB100 \
MEMB100 \
MEMB100 \
MEMB100 \
MEMB100 \
MEMB100 \
MEMB100 \
MEMB100
#define MEMB10000 \
MEMB1000 \
MEMB1000 \
MEMB1000 \
MEMB1000 \
MEMB1000 \
MEMB1000 \
MEMB1000 \
MEMB1000 \
MEMB1000 \
MEMB1000
struct big
{
MEMB1000;
};
struct huge
{
MEMB10000;
};
struct big big_used;
struct huge huge_used;
#else
int test_disabled;
#endif