Incorrect data detected in the nested float struct with x86/libffi on Linux/64bit
Anthony Green
green@moxielogic.com
Tue Jun 15 19:29:46 GMT 2021
Thank you, Jakub! This has been committed.
AG
On Tue, Jun 15, 2021 at 3:02 PM Jakub Jelinek <jakub@redhat.com> wrote:
> 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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