Incorrect data detected in the nested float struct with x86/libffi on Linux/64bit
Jakub Jelinek
jakub@redhat.com
Tue Jun 15 19:02:00 GMT 2021
On Tue, Jun 15, 2021 at 08:02:56PM +0200, Jakub Jelinek via Libffi-discuss wrote:
> On Wed, Jun 09, 2021 at 12:50:08PM -0400, Anthony Green wrote:
> > Thank you, Cheng. Are you able to submit this test case as a github pull
> > request? The resulting CI testing will give us a broader picture of where
> > we have problems.
>
> Comparing gcc/config/i386/ classify_argument and libffi classify_argument,
> I found two important differences.
>
> The first one seems the most important one, even GCC 3.2 included the bit
> offset (byte offset in libffi) in the calculation of number of words.
> And the other change is https://gcc.gnu.org/PR38781.
>
> With this patch the posted testcase works and the testsuite on x86_64-linux
> still passes, but haven't done more testing than that.
>
> Haven't tried yet to adapt one of the
> libffi/testsuite/libffi.call/nested_struct*.c tests to cover this though.
And here is one with a testcase (modified nested_struct2.c for it).
I'm unsure about the current relationship between the github and gcc
copy of libffi, shall it go to both, or just one of them and be
cherry-picked from there?
Tested on x86_64-linux.
2021-06-15 Jakub Jelinek <jakub@redhat.com>
* src/x86/ffi64.c (classify_argument): For FFI_TYPE_STRUCT set words
to number of words needed for type->size + byte_offset bytes rather
than just type->size bytes. Compute pos before the loop and check
total size of the structure.
* testsuite/libffi.call/nested_struct12.c: New test.
--- libffi/src/x86/ffi64.c.jj 2020-01-14 20:02:48.557583260 +0100
+++ libffi/src/x86/ffi64.c 2021-06-15 19:50:06.059108230 +0200
@@ -217,7 +217,8 @@ classify_argument (ffi_type *type, enum
case FFI_TYPE_STRUCT:
{
const size_t UNITS_PER_WORD = 8;
- size_t words = (type->size + UNITS_PER_WORD - 1) / UNITS_PER_WORD;
+ size_t words = (type->size + byte_offset + UNITS_PER_WORD - 1)
+ / UNITS_PER_WORD;
ffi_type **ptr;
int i;
enum x86_64_reg_class subclasses[MAX_CLASSES];
@@ -241,16 +242,16 @@ classify_argument (ffi_type *type, enum
/* Merge the fields of structure. */
for (ptr = type->elements; *ptr != NULL; ptr++)
{
- size_t num;
+ size_t num, pos;
byte_offset = ALIGN (byte_offset, (*ptr)->alignment);
num = classify_argument (*ptr, subclasses, byte_offset % 8);
if (num == 0)
return 0;
- for (i = 0; i < num; i++)
+ pos = byte_offset / 8;
+ for (i = 0; i < num && (i + pos) < words; i++)
{
- size_t pos = byte_offset / 8;
classes[i + pos] =
merge_classes (subclasses[i], classes[i + pos]);
}
--- libffi/testsuite/libffi.call/nested_struct12.c.jj 2021-06-15 20:31:43.327144303 +0200
+++ libffi/testsuite/libffi.call/nested_struct12.c 2021-06-15 20:47:13.129489263 +0200
@@ -0,0 +1,107 @@
+/* Area: ffi_call, closure_call
+ Purpose: Check structure passing.
+ Limitations: none.
+ PR: none.
+ Originator: <jincheng@ca.ibm.com> and <jakub@redhat.com> 20210609 */
+
+/* { dg-do run } */
+#include "ffitest.h"
+
+typedef struct A {
+ float a, b;
+} A;
+
+typedef struct B {
+ float x;
+ struct A y;
+} B;
+
+B B_fn(float b0, struct B b1)
+{
+ struct B result;
+
+ result.x = b0 + b1.x;
+ result.y.a = b0 + b1.y.a;
+ result.y.b = b0 + b1.y.b;
+
+ printf("%g %g %g %g: %g %g %g\n", b0, b1.x, b1.y.a, b1.y.b,
+ result.x, result.y.a, result.y.b);
+
+ return result;
+}
+
+static void
+B_gn(ffi_cif* cif __UNUSED__, void* resp, void** args,
+ void* userdata __UNUSED__)
+{
+ float b0;
+ struct B b1;
+
+ b0 = *(float*)(args[0]);
+ b1 = *(struct B*)(args[1]);
+
+ *(B*)resp = B_fn(b0, b1);
+}
+
+int main (void)
+{
+ ffi_cif cif;
+ void *code;
+ ffi_closure *pcl = ffi_closure_alloc(sizeof(ffi_closure), &code);
+ void* args_dbl[3];
+ ffi_type* cls_struct_fields[3];
+ ffi_type* cls_struct_fields1[3];
+ ffi_type cls_struct_type, cls_struct_type1;
+ ffi_type* dbl_arg_types[3];
+
+ float e_dbl = 12.125f;
+ struct B f_dbl = { 24.75f, { 31.625f, 32.25f } };
+
+ struct B res_dbl;
+
+ cls_struct_type.size = 0;
+ cls_struct_type.alignment = 0;
+ cls_struct_type.type = FFI_TYPE_STRUCT;
+ cls_struct_type.elements = cls_struct_fields;
+
+ cls_struct_type1.size = 0;
+ cls_struct_type1.alignment = 0;
+ cls_struct_type1.type = FFI_TYPE_STRUCT;
+ cls_struct_type1.elements = cls_struct_fields1;
+
+ cls_struct_fields[0] = &ffi_type_float;
+ cls_struct_fields[1] = &ffi_type_float;
+ cls_struct_fields[2] = NULL;
+
+ cls_struct_fields1[0] = &ffi_type_float;
+ cls_struct_fields1[1] = &cls_struct_type;
+ cls_struct_fields1[2] = NULL;
+
+
+ dbl_arg_types[0] = &ffi_type_float;
+ dbl_arg_types[1] = &cls_struct_type1;
+ dbl_arg_types[2] = NULL;
+
+ CHECK(ffi_prep_cif(&cif, FFI_DEFAULT_ABI, 2, &cls_struct_type1,
+ dbl_arg_types) == FFI_OK);
+
+ args_dbl[0] = &e_dbl;
+ args_dbl[1] = &f_dbl;
+ args_dbl[2] = NULL;
+
+ ffi_call(&cif, FFI_FN(B_fn), &res_dbl, args_dbl);
+ /* { dg-output "12.125 24.75 31.625 32.25: 36.875 43.75 44.375" } */
+ CHECK( res_dbl.x == (e_dbl + f_dbl.x));
+ CHECK( res_dbl.y.a == (e_dbl + f_dbl.y.a));
+ CHECK( res_dbl.y.b == (e_dbl + f_dbl.y.b));
+
+ CHECK(ffi_prep_closure_loc(pcl, &cif, B_gn, NULL, code) == FFI_OK);
+
+ res_dbl = ((B(*)(float, B))(code))(e_dbl, f_dbl);
+ /* { dg-output "\n12.125 24.75 31.625 32.25: 36.875 43.75 44.375" } */
+ CHECK( res_dbl.x == (e_dbl + f_dbl.x));
+ CHECK( res_dbl.y.a == (e_dbl + f_dbl.y.a));
+ CHECK( res_dbl.y.b == (e_dbl + f_dbl.y.b));
+
+ exit(0);
+}
Jakub
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