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ctf: fix PR debug/112878

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PR debug/112878: ICE: in ctf_add_slice, at ctfc.cc:499 with
_BitInt > 255 in a struct and -gctf1

The CTF generation in GCC does not have a mechanism to roll-back an
already added type.  In this testcase presented in the PR, we hit a
representation limit in CTF slices (for a member of a struct) and ICE,
after the type for struct (CTF_K_STRUCT) has already been added to the
container.

To exit gracefully instead, we now check for both the offset and size of
the bitfield to be explicitly <= 255.  If the check fails, we emit the
member with type CTF_K_UNKNOWN.  Note that, the value 255 stems from the
existing binutils libctf checks which were motivated to guard against
malformed inputs.

Although it is not accurate to say that this is a CTF representation
limit, mark the code with TBD_CTF_REPRESENTATION_LIMIT for now so that
this can be taken care of with the next format version bump, when
libctf's checks for the slice data can be lifted as well.

gcc/ChangeLog:
	PR debug/112878
	* dwarf2ctf.cc (gen_ctf_sou_type): Check for conditions before
	call to ctf_add_slice.  Use CTF_K_UNKNOWN type if fail.

gcc/testsuite/ChangeLog:
	PR debug/112878
	* gcc.dg/debug/ctf/ctf-bitfields-5.c: New test.
This commit is contained in:
Indu Bhagat 2024-04-10 17:27:52 -07:00
parent 0f3e76ee53
commit 5c869aa8a4
2 changed files with 27 additions and 5 deletions
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15
gcc/dwarf2ctf.cc
View file

@ -606,11 +606,16 @@ gen_ctf_sou_type (ctf_container_ref ctfc, dw_die_ref sou, uint32_t kind)
if (attr) if (attr)
bitpos += AT_unsigned (attr); bitpos += AT_unsigned (attr);
field_type_id = ctf_add_slice (ctfc, CTF_ADD_NONROOT, /* This is not precisely a TBD_CTF_REPRESENTATION_LIMIT, but
field_type_id, surely something to look at for the next format version bump
bitpos - field_location, for CTF. */
bitsize, if (bitsize <= 255 && (bitpos - field_location) <= 255)
c); field_type_id = ctf_add_slice (ctfc, CTF_ADD_NONROOT,
field_type_id,
bitpos - field_location,
bitsize, c);
else
field_type_id = gen_ctf_unknown_type (ctfc);
} }
/* Add the field type to the struct or union type. */ /* Add the field type to the struct or union type. */

17
gcc/testsuite/gcc.dg/debug/ctf/ctf-bitfields-5.c Normal file
View file

@ -0,0 +1,17 @@
/* Bitfield where the bit offset is > 255 is not allowed in CTF.
PR debug/112878.
This testcase is to ensure graceful handling. No slices are expected. */
/* { dg-do compile { target bitint } } */
/* { dg-options "-O0 -gctf -dA" } */
/* No slices are expected, but a struct with one member is expected.
CTF_K_UNKNOWN is also expected. */
/* { dg-final { scan-assembler-times "cts_type" 0 } } */
/* { dg-final { scan-assembler-times "\[\t \]0x1a000001\[\t \]+\[^\n\]*ctt_info" 1 } } */
/* { dg-final { scan-assembler-times "ascii \"unknown.0\"\[\t \]+\[^\n\]*ctf_string" 1 } } */
struct {
_BitInt(282) a : 280;
} b;