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.
>
> 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;
> +}
