https://gcc.gnu.org/g:d30def000abbc8d254a128751ac87a079cd10202
commit r15-6918-gd30def000abbc8d254a128751ac87a079cd10202
Author: Cupertino Miranda <cupertino.mira...@oracle.com>
Date: Wed Jan 15 14:25:44 2025 +0000
bpf: make sure CO-RE relocs are typed with struct BTF_KIND_STRUCT
Based on observation within bpf-next selftests and comparisson of GCC
and clang compiled code, the BPF loader expects all CO-RE relocations to
point to BTF non const and non volatile type nodes.
gcc/ChangeLog:
* btfout.cc (get_btf_kind): Remove static from function definition.
* config/bpf/btfext-out.cc (bpf_code_reloc_add): Check if CO-RE type
is not a const or volatile.
* ctfc.h (btf_dtd_kind): Add prototype for function.
gcc/testsuite/ChangeLog:
* gcc.target/bpf/core-attr-const.c: New test.
Diff:
---
gcc/btfout.cc | 2 +-
gcc/config/bpf/btfext-out.cc | 7 +++++
gcc/ctfc.h | 2 ++
gcc/testsuite/gcc.target/bpf/core-attr-const.c | 40 ++++++++++++++++++++++++++
4 files changed, 50 insertions(+), 1 deletion(-)
diff --git a/gcc/btfout.cc b/gcc/btfout.cc
index 16d5b7f97cc4..ff7ea42a9614 100644
--- a/gcc/btfout.cc
+++ b/gcc/btfout.cc
@@ -148,7 +148,7 @@ get_btf_kind (uint32_t ctf_kind)
/* Convenience wrapper around get_btf_kind for the common case. */
-static uint32_t
+uint32_t
btf_dtd_kind (ctf_dtdef_ref dtd)
{
if (!dtd)
diff --git a/gcc/config/bpf/btfext-out.cc b/gcc/config/bpf/btfext-out.cc
index ad5ce9655a7c..7cab59bb5400 100644
--- a/gcc/config/bpf/btfext-out.cc
+++ b/gcc/config/bpf/btfext-out.cc
@@ -298,6 +298,13 @@ bpf_core_reloc_add (const tree type, const char *
section_name,
ctf_container_ref ctfc = ctf_get_tu_ctfc ();
ctf_dtdef_ref dtd = ctf_lookup_tree_type (ctfc, type);
+ /* Make sure CO-RE type is never the const or volatile version. */
+ if ((btf_dtd_kind (dtd) == BTF_KIND_CONST
+ || btf_dtd_kind (dtd) == BTF_KIND_VOLATILE)
+ && kind >= BPF_RELO_FIELD_BYTE_OFFSET
+ && kind <= BPF_RELO_FIELD_RSHIFT_U64)
+ dtd = dtd->ref_type;
+
/* Buffer the access string in the auxiliary strtab. */
bpfcr->bpfcr_astr_off = 0;
gcc_assert (accessor != NULL);
diff --git a/gcc/ctfc.h b/gcc/ctfc.h
index 6a9baa56194c..32c73be6a412 100644
--- a/gcc/ctfc.h
+++ b/gcc/ctfc.h
@@ -465,4 +465,6 @@ extern void btf_mark_type_used (tree);
extern int ctfc_get_dtd_srcloc (ctf_dtdef_ref, ctf_srcloc_ref);
extern int ctfc_get_dvd_srcloc (ctf_dvdef_ref, ctf_srcloc_ref);
+extern uint32_t btf_dtd_kind (ctf_dtdef_ref dtd);
+
#endif /* GCC_CTFC_H */
diff --git a/gcc/testsuite/gcc.target/bpf/core-attr-const.c
b/gcc/testsuite/gcc.target/bpf/core-attr-const.c
new file mode 100644
index 000000000000..da6113a3faf1
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bpf/core-attr-const.c
@@ -0,0 +1,40 @@
+/* Test to make sure CO-RE access relocs point to non const versions of the
+ type. */
+
+/* { dg-do compile } */
+/* { dg-options "-O0 -dA -gbtf -mco-re -masm=normal" } */
+
+struct S {
+ int a;
+ int b;
+ int c;
+} __attribute__((preserve_access_index));
+
+void
+func (struct S * s)
+{
+ int *x;
+ int *y;
+ int *z;
+ struct S tmp;
+ const struct S *cs = s;
+ volatile struct S *vs = s;
+
+ /* 0:2 */
+ x = &(s->c);
+
+ /* 0:1 */
+ y = (int *) &(cs->b);
+
+ /* 0:1 */
+ z = (int *) &(vs->b);
+
+ *x = 4;
+ *y = 4;
+ *z = 4;
+}
+
+/* Both const and non const struct type should have the same bpfcr_type. */
+/* { dg-final { scan-assembler-times "0x1\t# bpfcr_type \\(struct S\\)" 1 } }
*/
+/* { dg-final { scan-assembler-times "0x1\t# bpfcr_type \\(const struct S\\)"
1 } } */
+/* { dg-final { scan-assembler-times "0x1\t# bpfcr_type \\(volatile struct
S\\)" 1 } } */
