Re: [PATCH] bpf: avoid issues with CO-RE and -gtoggle

["Jose E. Marchesi" <jose.marchesi@oracle.com>]

Hi Faust.
OK.  Thanks for the patch.

> Compiling a BPF program with CO-RE relocations (and BTF) while also
> passing -gtoggle led to an inconsistent state where CO-RE support was
> enabled but BTF would not be generated, and this was not caught by the
> existing option parsing.  This led to an ICE when generating the CO-RE
> relocation info, since BTF is required for CO-RE.
>
> Update bpf_option_override to avoid this case, and add a few tests for
> the interactions of these options.
>
> Tested on x86_64-linux-gnu host for bpf-unknown-none target.
>
> gcc/
> 	* config/bpf/bpf.cc (bpf_option_override): Improve handling of CO-RE
> 	options to avoid issues with -gtoggle.
>
> gcc/testsuite/
> 	* gcc.target/bpf/core-options-1.c: New test.
> 	* gcc.target/bpf/core-options-2.c: Likewise.
> 	* gcc.target/bpf/core-options-3.c: Likewise.
> ---
>  gcc/config/bpf/bpf.cc                         |  7 +++++--
>  gcc/testsuite/gcc.target/bpf/core-options-1.c | 15 +++++++++++++++
>  gcc/testsuite/gcc.target/bpf/core-options-2.c | 14 ++++++++++++++
>  gcc/testsuite/gcc.target/bpf/core-options-3.c |  5 +++++
>  4 files changed, 39 insertions(+), 2 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.target/bpf/core-options-1.c
>  create mode 100644 gcc/testsuite/gcc.target/bpf/core-options-2.c
>  create mode 100644 gcc/testsuite/gcc.target/bpf/core-options-3.c
>
> diff --git a/gcc/config/bpf/bpf.cc b/gcc/config/bpf/bpf.cc
> index 98fb755bb8b..e6ea211a2c6 100644
> --- a/gcc/config/bpf/bpf.cc
> +++ b/gcc/config/bpf/bpf.cc
> @@ -192,7 +192,8 @@ bpf_option_override (void)
>    init_machine_status = bpf_init_machine_status;
>  
>    /* BPF CO-RE support requires BTF debug info generation.  */
> -  if (TARGET_BPF_CORE && !btf_debuginfo_p ())
> +  if (TARGET_BPF_CORE
> +      && (!btf_debuginfo_p () || (debug_info_level < DINFO_LEVEL_NORMAL)))
>      error ("BPF CO-RE requires BTF debugging information, use %<-gbtf%>");
>  
>    /* BPF applications always generate .BTF.ext.  */
> @@ -215,7 +216,9 @@ bpf_option_override (void)
>  
>    /* -gbtf implies -mcore when using the BPF backend, unless -mno-co-re
>       is specified.  */
> -  if (btf_debuginfo_p () && !(target_flags_explicit & MASK_BPF_CORE))
> +  if (btf_debuginfo_p ()
> +      && (debug_info_level >= DINFO_LEVEL_NORMAL)
> +      && !(target_flags_explicit & MASK_BPF_CORE))
>      target_flags |= MASK_BPF_CORE;
>  
>    /* Determine available features from ISA setting (-mcpu=).  */
> diff --git a/gcc/testsuite/gcc.target/bpf/core-options-1.c b/gcc/testsuite/gcc.target/bpf/core-options-1.c
> new file mode 100644
> index 00000000000..7d8c677f239
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/bpf/core-options-1.c
> @@ -0,0 +1,15 @@
> +/* -gbtf for the BPF target should enable CO-RE support automatically.  */
> +/* { dg-do compile } */
> +/* { dg-options "-gbtf" } */
> +
> +struct A {
> +  int x;
> +  int y;
> +  char c;
> +};
> +
> +int
> +foo (struct A *a) {
> +  int y = __builtin_preserve_access_index (a->y);
> +  return y;
> +}
> diff --git a/gcc/testsuite/gcc.target/bpf/core-options-2.c b/gcc/testsuite/gcc.target/bpf/core-options-2.c
> new file mode 100644
> index 00000000000..8f466258e29
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/bpf/core-options-2.c
> @@ -0,0 +1,14 @@
> +/* { dg-do compile } */
> +/* { dg-options "-gbtf -gtoggle" } */
> +
> +struct A {
> +  int x;
> +  int y;
> +  char c;
> +};
> +
> +int
> +foo (struct A *a) {
> +  int y = __builtin_preserve_access_index (a->y); /* { dg-error "BPF CO-RE is required" } */
> +  return y;
> +}
> diff --git a/gcc/testsuite/gcc.target/bpf/core-options-3.c b/gcc/testsuite/gcc.target/bpf/core-options-3.c
> new file mode 100644
> index 00000000000..ca32a7c4012
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/bpf/core-options-3.c
> @@ -0,0 +1,5 @@
> +/* This combination of options tries to enable CO-RE without BTF, and should
> +   produce an error.  */
> +/* { dg-do compile } */
> +/* { dg-options "-gbtf -gtoggle -mco-re" } */
> +/* { dg-excess-errors "BPF CO-RE requires BTF debugging information" } */