From 791915db4273edbfb1952897cbf4c9745101c0e4 Mon Sep 17 00:00:00 2001 From: Nick Alcock Date: Mon, 5 Aug 2019 11:40:33 +0100 Subject: libctf: handle nonrepresentable types at link time GCC can emit references to type 0 to indicate that this type is one that is not representable in the version of CTF it emits (for instance, version 3 cannot encode vector types). Type 0 is already used in the function section to indicate padding inserted to skip functions we do not want to encode the type of, so using zero in this way is a good extension of the format: but libctf reports such types as ECTF_BADID, which is indistinguishable from file corruption via links to truly nonexistent types with IDs like 0xDEADBEEF etc, which we really do want to stop for. In particular, this stops all traversals of types dead at this point, preventing us from even dumping CTF files containing unrepresentable types to see what's going on! So add a new error, ECTF_NONREPRESENTABLE, which is returned by recursive type resolution when a reference to a zero type is found. (No zero type is ever emitted into the CTF file by GCC, only references to one). We can't do much with types that are ultimately nonrepresentable, but we can do enough to keep functioning. Adjust ctf_add_type to ensure that top-level types of type zero and structure and union members of ultimate type zero are simply skipped without reporting an error, so we can copy structures and unions that contain nonrepresentable members (skipping them and leaving a hole where they would be, so no consumers downstream of the linker need to worry about this): adjust the dumper so that we dump members of nonrepresentable types in a simple form that indicates nonrepresentability rather than terminating the dump, and do not falsely assume all errors to be -ENOMEM: adjust the linker so that types that fail to get added are simply skipped, so that both nonrepresentable types and outright errors do not terminate the type addition, which could skip many valid types and cause further errors when variables of those types are added. In future, when we gain the ability to call back to the linker to report link-time type resolution errors, we should report failures to add all but nonrepresentable types. But we can't do that yet. v5: Fix tabdamage. include/ * ctf-api.h (ECTF_NONREPRESENTABLE): New. libctf/ * ctf-types.c (ctf_type_resolve): Return ECTF_NONREPRESENTABLE on type zero. * ctf-create.c (ctf_add_type): Detect and skip nonrepresentable members and types. (ctf_add_variable): Likewise for variables pointing to them. * ctf-link.c (ctf_link_one_type): Do not warn for nonrepresentable type link failure, but do warn for others. * ctf-dump.c (ctf_dump_format_type): Likewise. Do not assume all errors to be ENOMEM. (ctf_dump_member): Likewise. (ctf_dump_type): Likewise. (ctf_dump_header_strfield): Do not assume all errors to be ENOMEM. (ctf_dump_header_sectfield): Do not assume all errors to be ENOMEM. (ctf_dump_header): Likewise. (ctf_dump_label): likewise. (ctf_dump_objts): likewise. (ctf_dump_funcs): likewise. (ctf_dump_var): likewise. (ctf_dump_str): Likewise. --- include/ChangeLog | 4 ++++ include/ctf-api.h | 3 ++- 2 files changed, 6 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/ChangeLog b/include/ChangeLog index a0d3c10..1f95342 100644 --- a/include/ChangeLog +++ b/include/ChangeLog @@ -1,3 +1,7 @@ +2019-08-05 Nick Alcock + + * ctf-api.h (ECTF_NONREPRESENTABLE): New. + 2019-09-23 Nick Alcock * ctf-api.h: Note the instability of the ctf_link interfaces. diff --git a/include/ctf-api.h b/include/ctf-api.h index 674860d..b83ddc7 100644 --- a/include/ctf-api.h +++ b/include/ctf-api.h @@ -203,7 +203,8 @@ enum ECTF_DUMPSECTUNKNOWN, /* Unknown section number in dump. */ ECTF_DUMPSECTCHANGED, /* Section changed in middle of dump. */ ECTF_NOTYET, /* Feature not yet implemented. */ - ECTF_INTERNAL /* Internal error in link. */ + ECTF_INTERNAL, /* Internal error in link. */ + ECTF_NONREPRESENTABLE /* Type not representable in CTF. */ }; /* The CTF data model is inferred to be the caller's data model or the data -- cgit v1.1