Re: [PATCH v2 04/16] Add libc ABI extension kludge for baseline-violating libdl symbols

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 31/05/2021 11:11, Florian Weimer via Libc-alpha wrote:
> Some targets have a GLIBC_2.0 baseline for libdl, while using
> GLIBC_2.2 for libc.  This means that the generated libc.map file
> does not have any version nodes for GLIBC_2.0 or GLIBC_2.1.  However,
> moving symbols from libdl into libc needs such version nodes.
> (Future symbol moves from librt will need this as well.)
> 
> This kludge is only necessary for symbols predating GLIBC_2.2 because
> the affected targets use GLIBC_2.2 as the baseline for libc.  Given
> the small number and fixexd set of affected architectures, no generic

Typo 'fixexd'

> mechanism is implemented, and instead the map file fragment is
> hard-coded in scripts/versions.mk.
> 
> The compat_symbol macro already emits the appropriate version strings,
> so no adjustments are needed there.

I guess this quite specific mismatched version issue justify this
ad-hoc solution. 

LGTM, thanks. There is only a small nit regarding the version tag
name used.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  scripts/versions.awk                          | 26 ++++++++++++++++++-
>  sysdeps/unix/sysv/linux/hppa/Versions         |  1 +
>  sysdeps/unix/sysv/linux/ia64/Versions         |  1 +
>  sysdeps/unix/sysv/linux/sh/Versions           |  1 +
>  .../unix/sysv/linux/sparc/sparc64/Versions    |  1 +
>  5 files changed, 29 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/versions.awk b/scripts/versions.awk
> index a7154480e3..1e8d8e4dc5 100644
> --- a/scripts/versions.awk
> +++ b/scripts/versions.awk
> @@ -93,6 +93,26 @@ function ord(c) {
>    printf("%s %s %s\n", actlib, sortver, $0) | sort;
>  }
>  
> +# Some targets do not set the ABI baseline for libdl.  As a result,
> +# symbols originally in libdl need to be moved under historic symbol
> +# versions, without altering the baseline version for libc itself.
> +/^ *!libc_abi_extension/ {

Maybe use a different name like 'libc_compat_versions', the 'extension'
wording does not really fits in what it is providing.

> +    libc_abi_extension_active = 1;
> +}
> +
> +function libc_abi_extension() {
> +    # No local: * here, so that we do not have to update this script
> +    # if symbols are moved into libc.  The abilist files and the other
> +    # targets (with a real GLIBC_2.0 baseline) provide testing
> +    # coverage.
> +    printf("\
> +GLIBC_2.0 {\n\
> +};\n\
> +GLIBC_2.1 {\n\
> +} GLIBC_2.0;\n\
> +") > outfile;
> +    return "GLIBC_2.1";
> +}
>  
>  function closeversion(name, oldname) {
>    printf("  local:\n    *;\n") > outfile;
> @@ -154,7 +174,11 @@ END {
>        oldlib = $1;
>        real_outfile = buildroot oldlib ".map";
>        outfile = real_outfile "T";
> -      veryoldver = "";
> +      if ($1 == "libc" && libc_abi_extension_active) {
> +	  veryoldver = libc_abi_extension();
> +      } else {
> +	  veryoldver = "";
> +      }
>        printf(" %s.map", oldlib);
>      }
>      if ($2 != oldver) {

Ok.

> diff --git a/sysdeps/unix/sysv/linux/hppa/Versions b/sysdeps/unix/sysv/linux/hppa/Versions
> index 9532d207fc..8969fc08af 100644
> --- a/sysdeps/unix/sysv/linux/hppa/Versions
> +++ b/sysdeps/unix/sysv/linux/hppa/Versions
> @@ -1,3 +1,4 @@
> +!libc_abi_extension
>  libc {
>    GLIBC_2.1 {
>      _sys_errlist; sys_errlist; _sys_nerr; sys_nerr;
> diff --git a/sysdeps/unix/sysv/linux/ia64/Versions b/sysdeps/unix/sysv/linux/ia64/Versions
> index f6994151aa..7cac57a8e1 100644
> --- a/sysdeps/unix/sysv/linux/ia64/Versions
> +++ b/sysdeps/unix/sysv/linux/ia64/Versions
> @@ -1,3 +1,4 @@
> +!libc_abi_extension
>  libc {
>    GLIBC_2.2 {
>      ioperm; iopl;
> diff --git a/sysdeps/unix/sysv/linux/sh/Versions b/sysdeps/unix/sysv/linux/sh/Versions
> index 19ba1d8d91..fc89ff1c18 100644
> --- a/sysdeps/unix/sysv/linux/sh/Versions
> +++ b/sysdeps/unix/sysv/linux/sh/Versions
> @@ -1,3 +1,4 @@
> +!libc_abi_extension
>  libc {
>    GLIBC_2.2 {
>      # functions used in other libraries
> diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/Versions b/sysdeps/unix/sysv/linux/sparc/sparc64/Versions
> index fbea1bb2ef..3059d56f80 100644
> --- a/sysdeps/unix/sysv/linux/sparc/sparc64/Versions
> +++ b/sysdeps/unix/sysv/linux/sparc/sparc64/Versions
> @@ -1,3 +1,4 @@
> +!libc_abi_extension
>  libc {
>    GLIBC_2.0 {
>      # Exception handling support functions from libgcc
>