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author | Bernhard Schommer <bschommer@users.noreply.github.com> | 2020-02-20 18:55:34 +0100 |
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committer | GitHub <noreply@github.com> | 2020-02-20 18:55:34 +0100 |
commit | a9eaf4897c825093aba2137ff76e56bfbf1e72d5 (patch) | |
tree | c7a0787cd0a1a716a3ac448683c3cda75ffb6486 /cfrontend | |
parent | 797829058aedff543c1f30b269b8fc8a0be35e36 (diff) | |
download | compcert-a9eaf4897c825093aba2137ff76e56bfbf1e72d5.tar.gz compcert-a9eaf4897c825093aba2137ff76e56bfbf1e72d5.zip |
More precise determination of small data accesses (#220)
We can get linker errors for addresses of the form "symbol + offset"
where "symbol" is in the small data area and "offset" is large enough
to overflow the relative displacement from the SDA base register.
To avoid this, this commit enriches `C2C.atom_is_small_data`,
which is the implementation of `Asm.symbol_is_small_data` in the PPC port,
with a check that the offset is within the bounds of the symbol.
If it is not, `Asm.symbol_is_small_data` returns `false` and Asmgen produces
an absolute addressing instead of a SDA-relative addressing.
To implement the check, we record the sizes of symbols in the atom table,
just like we already record their alignments.
Diffstat (limited to 'cfrontend')
-rw-r--r-- | cfrontend/C2C.ml | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/cfrontend/C2C.ml b/cfrontend/C2C.ml index 9ae7bbd9..293e79f0 100644 --- a/cfrontend/C2C.ml +++ b/cfrontend/C2C.ml @@ -33,6 +33,7 @@ type inline_status = type atom_info = { a_storage: C.storage; (* storage class *) + a_size: int64 option; (* size in bytes *) a_alignment: int option; (* alignment *) a_sections: Sections.section_name list; (* in which section to put it *) (* 1 section for data, 3 sections (code/lit/jumptbl) for functions *) @@ -72,9 +73,14 @@ let atom_sections a = with Not_found -> [] -let atom_is_small_data a ofs = +let atom_is_small_data a ofs = try - (Hashtbl.find decl_atom a).a_access = Sections.Access_near + let info = Hashtbl.find decl_atom a in + info.a_access = Sections.Access_near + && (match info.a_size with + | None -> false + | Some sz -> + let ofs = camlint64_of_ptrofs ofs in 0L <= ofs && ofs < sz) with Not_found -> false @@ -352,6 +358,7 @@ let name_for_string_literal s = Hashtbl.add decl_atom id { a_storage = C.Storage_static; a_alignment = Some 1; + a_size = Some (Int64.of_int (String.length s + 1)); a_sections = [Sections.for_stringlit()]; a_access = Sections.Access_default; a_inline = No_specifier; @@ -379,9 +386,12 @@ let name_for_wide_string_literal s = incr stringNum; let name = Printf.sprintf "__stringlit_%d" !stringNum in let id = intern_string name in + let wchar_size = Machine.((!config).sizeof_wchar) in Hashtbl.add decl_atom id { a_storage = C.Storage_static; - a_alignment = Some Machine.((!config).sizeof_wchar); + a_alignment = Some wchar_size; + a_size = Some (Int64.(mul (of_int (List.length s + 1)) + (of_int wchar_size))); a_sections = [Sections.for_stringlit()]; a_access = Sections.Access_default; a_inline = No_specifier; @@ -1223,6 +1233,7 @@ let convertFundef loc env fd = Hashtbl.add decl_atom id' { a_storage = fd.fd_storage; a_alignment = None; + a_size = None; a_sections = Sections.for_function env id' fd.fd_attrib; a_access = Sections.Access_default; a_inline = inline; @@ -1309,6 +1320,7 @@ let convertGlobvar loc env (sto, id, ty, optinit) = Hashtbl.add decl_atom id' { a_storage = sto; a_alignment = Some (Z.to_int al); + a_size = Some (Z.to_int64 sz); a_sections = [section]; a_access = access; a_inline = No_specifier; |