> On 7/12/22 08:13, Jose E. Marchesi via Gcc-patches wrote:
>>
>> The kernel bpftool expects BTF_KIND_FUNC entries in BTF to include an
>> annotation reflecting the linkage of functions (static, global). For
>> whatever reason they abuse the `vlen' field of the BTF_KIND_FUNC entry
>> instead of adding a variable-part to the record like it is done with
>> other entry kinds.
>>
>> This patch makes GCC to include this linkage info in BTF_KIND_FUNC
>> entries.
>>
>> Tested in bpf-unknown-none target.
>
> LGTM
> Thanks.
Pushed to master.
Thanks.
>>
>> gcc/ChangeLog:
>>
>> PR debug/106263
>> * ctfc.h (struct ctf_dtdef): Add field linkage.
>> * ctfc.cc (ctf_add_function): Set ctti_linkage.
>> * dwarf2ctf.cc (gen_ctf_function_type): Pass a linkage for
>> function types and subprograms.
>> * btfout.cc (btf_asm_func_type): Emit linkage information for the
>> function.
>> (btf_dtd_emit_preprocess_cb): Propagate the linkage information
>> for functions.
>>
>> gcc/testsuite/ChangeLog:
>>
>> PR debug/106263
>> * gcc.dg/debug/btf/btf-function-4.c: New test.
>> * gcc.dg/debug/btf/btf-function-5.c: Likewise.
>> ---
>> gcc/btfout.cc | 6 +++++-
>> gcc/ctfc.cc | 3 ++-
>> gcc/ctfc.h | 3 ++-
>> gcc/dwarf2ctf.cc | 4 +++-
>> gcc/testsuite/gcc.dg/debug/btf/btf-function-4.c | 14 ++++++++++++++
>> gcc/testsuite/gcc.dg/debug/btf/btf-function-5.c | 14 ++++++++++++++
>> 6 files changed, 40 insertions(+), 4 deletions(-)
>> create mode 100644 gcc/testsuite/gcc.dg/debug/btf/btf-function-4.c
>> create mode 100644 gcc/testsuite/gcc.dg/debug/btf/btf-function-5.c
>>
>> diff --git a/gcc/btfout.cc b/gcc/btfout.cc
>> index 31af50521da..594cba84910 100644
>> --- a/gcc/btfout.cc
>> +++ b/gcc/btfout.cc
>> @@ -463,6 +463,7 @@ btf_dtd_emit_preprocess_cb (ctf_container_ref ctfc,
>> ctf_dtdef_ref dtd)
>> ctf_dtdef_ref func_dtd = ggc_cleared_alloc<ctf_dtdef_t> ();
>> func_dtd->dtd_data = dtd->dtd_data;
>> func_dtd->dtd_data.ctti_type = dtd->dtd_type;
>> + func_dtd->linkage = dtd->linkage;
>>
>> vec_safe_push (funcs, func_dtd);
>> num_types_created++;
>> @@ -740,7 +741,10 @@ static void
>> btf_asm_func_type (ctf_dtdef_ref dtd)
>> {
>> dw2_asm_output_data (4, dtd->dtd_data.ctti_name, "btt_name");
>> - dw2_asm_output_data (4, BTF_TYPE_INFO (BTF_KIND_FUNC, 0, 0), "btt_info");
>> + dw2_asm_output_data (4, BTF_TYPE_INFO (BTF_KIND_FUNC, 0,
>> + dtd->linkage),
>> + "btt_info: kind=%u, kflag=%u, linkage=%u",
>> + BTF_KIND_FUNC, 0, dtd->linkage);
>> dw2_asm_output_data (4, get_btf_id (dtd->dtd_data.ctti_type), "btt_type");
>> }
>>
>> diff --git a/gcc/ctfc.cc b/gcc/ctfc.cc
>> index f24e7bff948..9773358a475 100644
>> --- a/gcc/ctfc.cc
>> +++ b/gcc/ctfc.cc
>> @@ -777,7 +777,7 @@ ctf_add_function_arg (ctf_container_ref ctfc, dw_die_ref
>> func,
>> ctf_id_t
>> ctf_add_function (ctf_container_ref ctfc, uint32_t flag, const char * name,
>> const ctf_funcinfo_t * ctc, dw_die_ref die,
>> - bool from_global_func)
>> + bool from_global_func, int linkage)
>> {
>> ctf_dtdef_ref dtd;
>> ctf_id_t type;
>> @@ -791,6 +791,7 @@ ctf_add_function (ctf_container_ref ctfc, uint32_t flag,
>> const char * name,
>> type = ctf_add_generic (ctfc, flag, name, &dtd, die);
>>
>> dtd->from_global_func = from_global_func;
>> + dtd->linkage = linkage;
>> dtd->dtd_data.ctti_info = CTF_TYPE_INFO (CTF_K_FUNCTION, flag, vlen);
>> /* Caller must make sure CTF types for ctc->ctc_return are already added.
>> */
>> dtd->dtd_data.ctti_type = (uint32_t) ctc->ctc_return;
>> diff --git a/gcc/ctfc.h b/gcc/ctfc.h
>> index 001e544ef08..bcf3a43ae1b 100644
>> --- a/gcc/ctfc.h
>> +++ b/gcc/ctfc.h
>> @@ -161,6 +161,7 @@ struct GTY ((for_user)) ctf_dtdef
>> ctf_itype_t dtd_data; /* Type node. */
>> bool from_global_func; /* Whether this type was added from a global
>> function. */
>> + uint32_t linkage; /* Used in function types. 0=local,
>> 1=global. */
>> union GTY ((desc ("ctf_dtu_d_union_selector (&%1)")))
>> {
>> /* struct, union, or enum. */
>> @@ -423,7 +424,7 @@ extern ctf_id_t ctf_add_forward (ctf_container_ref,
>> uint32_t, const char *,
>> extern ctf_id_t ctf_add_typedef (ctf_container_ref, uint32_t, const char *,
>> ctf_id_t, dw_die_ref);
>> extern ctf_id_t ctf_add_function (ctf_container_ref, uint32_t, const char *,
>> - const ctf_funcinfo_t *, dw_die_ref, bool);
>> + const ctf_funcinfo_t *, dw_die_ref, bool,
>> int);
>> extern ctf_id_t ctf_add_sou (ctf_container_ref, uint32_t, const char *,
>> uint32_t, size_t, dw_die_ref);
>>
>> diff --git a/gcc/dwarf2ctf.cc b/gcc/dwarf2ctf.cc
>> index a6329ab6ee4..397100004c2 100644
>> --- a/gcc/dwarf2ctf.cc
>> +++ b/gcc/dwarf2ctf.cc
>> @@ -644,6 +644,7 @@ gen_ctf_function_type (ctf_container_ref ctfc,
>> dw_die_ref function,
>>
>> ctf_funcinfo_t func_info;
>> uint32_t num_args = 0;
>> + int linkage = get_AT_flag (function, DW_AT_external);
>>
>> ctf_id_t return_type_id;
>> ctf_id_t function_type_id;
>> @@ -687,7 +688,8 @@ gen_ctf_function_type (ctf_container_ref ctfc,
>> dw_die_ref function,
>> function_name,
>> (const ctf_funcinfo_t *)&func_info,
>> function,
>> - from_global_func);
>> + from_global_func,
>> + linkage);
>>
>> /* Second pass on formals: generate the CTF types corresponding to
>> them and add them as CTF function args. */
>> diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-function-4.c
>> b/gcc/testsuite/gcc.dg/debug/btf/btf-function-4.c
>> new file mode 100644
>> index 00000000000..fd3124488f5
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.dg/debug/btf/btf-function-4.c
>> @@ -0,0 +1,14 @@
>> +/* Test BTF linkage for functions.
>> +
>> + We expect to see one BTF_KIND_FUNC type with static linkage encoded in
>> the
>> + BTF type's vlen field. */
>> +
>> +/* { dg-do compile } */
>> +/* { dg-options "-O0 -gbtf -dA" } */
>> +
>> +/* { dg-final { scan-assembler-times "btt_info: kind=12, kflag=0,
>> linkage=0" 1 } } */
>> +
>> +static int funfoo (void)
>> +{
>> + return 0;
>> +}
>> diff --git a/gcc/testsuite/gcc.dg/debug/btf/btf-function-5.c
>> b/gcc/testsuite/gcc.dg/debug/btf/btf-function-5.c
>> new file mode 100644
>> index 00000000000..12ee97fb5e3
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.dg/debug/btf/btf-function-5.c
>> @@ -0,0 +1,14 @@
>> +/* Test BTF linkage for functions.
>> +
>> + We expect to see one BTF_KIND_FUNC type with global linkage encoded in
>> the
>> + BTF type's vlen field. */
>> +
>> +/* { dg-do compile } */
>> +/* { dg-options "-O0 -gbtf -dA" } */
>> +
>> +/* { dg-final { scan-assembler-times "btt_info: kind=12, kflag=0,
>> linkage=1" 1 } } */
>> +
>> +int funfoo (void)
>> +{
>> + return 0;
>> +}
