[gcc r14-9876] btf: emit symbol refs in DATASEC entries only for BPF [PR114608]

[gcc r14-9876] btf: emit symbol refs in DATASEC entries only for BPF [PR114608]

[David Faust]

https://gcc.gnu.org/g:8075477f81ae8d0abf64b80dfbd179151f91b417

commit r14-9876-g8075477f81ae8d0abf64b80dfbd179151f91b417
Author: David Faust <david.faust@oracle.com>
Date:   Mon Apr 8 11:10:41 2024 -0700

    btf: emit symbol refs in DATASEC entries only for BPF [PR114608]
    
    The behavior introduced in
      fa60ac54964 btf: Emit labels in DATASEC bts_offset entries.
    
    is only fully correct when compiling for the BPF target with BPF CO-RE
    enabled.  In other cases, depending on optimizations, it can result in
    an incorrect symbol reference in the entry bts_offset field for a symbol
    which may not be emitted at all, causing link-time undefined symbol
    reference errors like in PR114608.
    
    The offending bts_offset field of BTF_KIND_DATASEC entries is in reality
    only currently useful to consumers of BTF information for BPF programs
    anyway.  Correct the regression by only emitting symbol references in
    these entries when compiling for the BPF target.  For other targets, the
    behavior returns to that prior to fa60ac54964.
    
    The underlying cause is related to PR 113566 "btf: incorrect
    BTF_KIND_DATASEC entries for variables which are optimized out." A
    complete fix for 113566 is more involved and unsuitable for stage 4,
    but will be addressed in the near future.
    
    gcc/
            PR debug/114608
            * btfout.cc (btf_asm_datasec_entry): Only emit a symbol reference when
            generating BTF for BPF CO-RE target.
    
    gcc/testsuite/
            PR debug/114608
            * gcc.dg/debug/btf/btf-datasec-1.c: Check bts_offset symbol references
            only for BPF target.
            * gcc.dg/debug/btf/btf-datasec-2.c: Likewise.
            * gcc.dg/debug/btf/btf-pr106773.c: Likewise.

Diff:
---
 gcc/btfout.cc                                  |  2 +-
 gcc/testsuite/gcc.dg/debug/btf/btf-datasec-1.c | 10 ++++++----
 gcc/testsuite/gcc.dg/debug/btf/btf-datasec-2.c |  7 ++++---
 gcc/testsuite/gcc.dg/debug/btf/btf-pr106773.c  |  3 ++-
 4 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/gcc/btfout.cc b/gcc/btfout.cc
index 2e2b3524e83..4a8ec4d1ff0 100644
--- a/gcc/btfout.cc
+++ b/gcc/btfout.cc
@@ -1045,7 +1045,7 @@ btf_asm_datasec_entry (ctf_container_ref ctfc, struct btf_var_secinfo info)
 {
   const char *symbol_name = get_name_for_datasec_entry (ctfc, info.type);
   btf_asm_type_ref ("bts_type", ctfc, info.type);
-  if (symbol_name == NULL)
+  if (!btf_with_core_debuginfo_p () || symbol_name == NULL)
     dw2_asm_output_data (4, info.offset, "bts_offset");
   else
     dw2_asm_output_offset (4, symbol_name, NULL, "bts_offset");
diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-datasec-1.c b/gcc/testsuite/gcc.dg/debug/btf/btf-datasec-1.c
index c8ebe5d07ca..15b76259218 100644
--- a/gcc/testsuite/gcc.dg/debug/btf/btf-datasec-1.c
+++ b/gcc/testsuite/gcc.dg/debug/btf/btf-datasec-1.c
@@ -19,10 +19,12 @@
 /* { dg-final { scan-assembler-times "0xf000003\[\t \]+\[^\n\]*btt_info" 2 } } */
 /* { dg-final { scan-assembler-times "0xf000001\[\t \]+\[^\n\]*btt_info" 1 } } */
 
-/* The offset entry for each variable in a DATSEC should contain a label.  */
-/* { dg-final { scan-assembler-times "(?:(?:\\.4byte|\\.long|data4\\.ua|\\.ualong|\\.uaword|\\.dword|long|dc\\.l|\\.word)\[\t \]|\\.vbyte\t4,\[\t \]?)_?\[a-e\]\[\t \]+\[^\n\]*bts_offset" 5 } } */
-/* { dg-final { scan-assembler-times "my_cstruct\[\t \]+\[^\n\]*bts_offset" 1 } } */
-/* { dg-final { scan-assembler-times "bigarr\[\t \]+\[^\n\]*bts_offset" 1 } } */
+/* { dg-final { scan-assembler-times "0\[\t \]+\[^\n\]*bts_offset" 7 { target { ! bpf-*-* } } } } */
+
+/* For BPF target the offset entry for each variable in a DATSEC should contain a label.  */
+/* { dg-final { scan-assembler-times ".4byte\[\t \]\[a-e\]\[\t \]+\[^\n\]*bts_offset" 5 { target bpf-*-* } } } */
+/* { dg-final { scan-assembler-times "my_cstruct\[\t \]+\[^\n\]*bts_offset" 1 { target bpf-*-* } } } */
+/* { dg-final { scan-assembler-times "bigarr\[\t \]+\[^\n\]*bts_offset" 1 { target bpf-*-* } } } */
 
 /* Check that strings for each DATASEC have been added to the BTF string table.  */
 /* { dg-final { scan-assembler-times "ascii \".data.0\"\[\t \]+\[^\n\]*btf_aux_string" 1 } } */
diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-datasec-2.c b/gcc/testsuite/gcc.dg/debug/btf/btf-datasec-2.c
index 857d830e446..a89a239a504 100644
--- a/gcc/testsuite/gcc.dg/debug/btf/btf-datasec-2.c
+++ b/gcc/testsuite/gcc.dg/debug/btf/btf-datasec-2.c
@@ -10,9 +10,10 @@
 /* { dg-final { scan-assembler-times " BTF_KIND_DATASEC '.bar_sec'\[\\r\\n\]+\[^\\r\\n\]*0xf000002\[\t \]+\[^\n\]*btt_info" 1 } } */
 
 /* Function entries should have offset with a label and size of 0 at compile time.  */
-/* { dg-final { scan-assembler-times "chacha\[\t \]+\[^\n\]*bts_offset" 1 } } */
-/* { dg-final { scan-assembler-times "bar\[\t \]+\[^\n\]*bts_offset" 1 } } */
-/* { dg-final { scan-assembler-times "foo\[\t \]+\[^\n\]*bts_offset" 1 } } */
+/* { dg-final { scan-assembler-times "chacha\[\t \]+\[^\n\]*bts_offset" 1 { target { bpf-*-* } }} } */
+/* { dg-final { scan-assembler-times "bar\[\t \]+\[^\n\]*bts_offset" 1 { target { bpf-*-* } } } } */
+/* { dg-final { scan-assembler-times "foo\[\t \]+\[^\n\]*bts_offset" 1 { target { bpf-*-* } } } } */
+/* { dg-final { scan-assembler-times "0\[\t \]+\[^\n\]*bts_offset" 3 { target { ! bpf-*-* } } } } */
 
 /* { dg-final { scan-assembler-times "0\[\t \]+\[^\n\]*bts_size" 3 } } */
 
diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-pr106773.c b/gcc/testsuite/gcc.dg/debug/btf/btf-pr106773.c
index c06220eb520..4e3da27d20d 100644
--- a/gcc/testsuite/gcc.dg/debug/btf/btf-pr106773.c
+++ b/gcc/testsuite/gcc.dg/debug/btf/btf-pr106773.c
@@ -11,7 +11,8 @@
 
 /* { dg-final { scan-assembler-times "ascii \"foo.0\"\[\t \]+\[^\n\]*btf_string" 1 } } */
 
-/* { dg-final { scan-assembler-times "foo\[\t \]+\[^\n\]*bts_offset" 1 } } */
+/* { dg-final { scan-assembler-times "foo\[\t \]+\[^\n\]*bts_offset" 1 { target { bpf-*-* } } } } */
+/* { dg-final { scan-assembler-times "0\[\t \]+\[^\n\]*bts_offset" 1 { target { ! bpf-*-* } } } } */
 /* { dg-final { scan-assembler-times "1\[\t \]+\[^\n\]*bts_size" 1 } } */
 
 extern const void foo __attribute__((weak)) __attribute__((section (".ksyms")));