Re: [PATCH 2/2] RISC-V: Check for conflicting extensions when the linker merges arch attributes

On Mon, Jul 6, 2026 at 7:46 PM Ethan Y. C. Liang <[email protected]>
wrote:

> The linker validates the arch of each input when parsing it, but never
> checks the merged arch as a whole, so conflicting extensions could
> silently slip through.  The merge can even imply extensions that
> neither input implies alone, e.g. `c' from one input and `d' from
> another imply `zcd', which conflicts with `zcmp'.
>
> After merging the input archs, add the implicit extensions to the
> merged arch, then run the conflict checks on it and reject the merge
> if any conflict is found.  Add tests for such merges.
> ---
>  bfd/elfxx-riscv.c                                      | 8 ++++++++
>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.d  | 5 +++++
>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.l  | 2 ++
>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01a.s | 1 +
>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01b.s | 1 +
>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.d  | 5 +++++
>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.l  | 2 ++
>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02a.s | 1 +
>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02b.s | 1 +
>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.d  | 5 +++++
>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.l  | 2 ++
>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03a.s | 1 +
>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03b.s | 1 +
>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.d  | 5 +++++
>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.l  | 2 ++
>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04a.s | 1 +
>  ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04b.s | 1 +
>  ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp             | 4 ++++
>  18 files changed, 48 insertions(+)
>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.d
>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.l
>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01a.s
>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01b.s
>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.d
>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.l
>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02a.s
>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02b.s
>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.d
>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.l
>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03a.s
>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03b.s
>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.d
>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.l
>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04a.s
>  create mode 100644 ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04b.s
>
> diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
> index fa2f1759f31..128c0eda8c4 100644
> --- a/bfd/elfxx-riscv.c
> +++ b/bfd/elfxx-riscv.c
> @@ -3750,6 +3750,14 @@ riscv_merge_arch_attr_info (bfd *ibfd, char
> *in_arch, char *out_arch,
>        goto cleanup;
>      }
>
> +  /* Add the implicit subsets implied by the merged subset list, then
> +     check if the result is conflicting.  */
> +  riscv_parse_subset_t riscv_rps_ld_merged =
> +    {&merged_subsets, _bfd_error_handler, &xlen_in, NULL, false};

+  riscv_parse_add_implicit_subsets (&riscv_rps_ld_merged);
> +  if (!riscv_parse_check_conflicts (&riscv_rps_ld_merged))
> +    goto cleanup;
> +
>

Looks reasonable to call riscv_parse_check_conflicts for the merged
architecture string.  But do we need to call riscv_parse_add_implicit_subsets?
Since I checked all current check_implicit_* functions
(always/for_i/for_zcf/for_zcd), I think all implicit extensions should be
added in the each input object already.

Thanks
Nelson


>    /* Free the previous merged_arch_str which called xmalloc.  */
>    free (merged_arch_str);
>
> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.d
> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.d
> new file mode 100644
> index 00000000000..f99677cb767
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.d
> @@ -0,0 +1,5 @@
> +#source: attr-merge-arch-failed-01a.s
> +#source: attr-merge-arch-failed-01b.s
> +#as: -mabi=ilp32
> +#ld: -r -m[riscv_choose_ilp32_emul]
> +#error_output: attr-merge-arch-failed-01.l
> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.l
> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.l
> new file mode 100644
> index 00000000000..ad6d2630211
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01.l
> @@ -0,0 +1,2 @@
> +.*: `zfinx' conflicts with the `f/d/q/zfh/zfhmin' extension
> +.*: failed to merge target specific data of file .*
> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01a.s
> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01a.s
> new file mode 100644
> index 00000000000..8f2a98f95f3
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01a.s
> @@ -0,0 +1 @@
> +       .attribute arch, "rv32i_zfinx"
> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01b.s
> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01b.s
> new file mode 100644
> index 00000000000..a44b2a0d346
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-01b.s
> @@ -0,0 +1 @@
> +       .attribute arch, "rv32if"
> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.d
> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.d
> new file mode 100644
> index 00000000000..4fb1980c97d
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.d
> @@ -0,0 +1,5 @@
> +#source: attr-merge-arch-failed-02a.s
> +#source: attr-merge-arch-failed-02b.s
> +#as: -mabi=ilp32
> +#ld: -r -m[riscv_choose_ilp32_emul]
> +#error_output: attr-merge-arch-failed-02.l
> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.l
> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.l
> new file mode 100644
> index 00000000000..930e03123e1
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02.l
> @@ -0,0 +1,2 @@
> +.*: zcmp' is incompatible with `d' and `c', or `zcd' extension
> +.*: failed to merge target specific data of file .*
> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02a.s
> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02a.s
> new file mode 100644
> index 00000000000..3f79059d5d0
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02a.s
> @@ -0,0 +1 @@
> +       .attribute arch, "rv32i_zcmp"
> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02b.s
> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02b.s
> new file mode 100644
> index 00000000000..95bfe1f6d9f
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-02b.s
> @@ -0,0 +1 @@
> +       .attribute arch, "rv32i_zcd"
> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.d
> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.d
> new file mode 100644
> index 00000000000..def49c3fb3f
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.d
> @@ -0,0 +1,5 @@
> +#source: attr-merge-arch-failed-03a.s
> +#source: attr-merge-arch-failed-03b.s
> +#as: -mabi=ilp32
> +#ld: -r -m[riscv_choose_ilp32_emul]
> +#error_output: attr-merge-arch-failed-03.l
> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.l
> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.l
> new file mode 100644
> index 00000000000..d9075d0c30e
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03.l
> @@ -0,0 +1,2 @@
> +.*: `zclsd' conflicts with the `c\+f'/`zcf' extension
> +.*: failed to merge target specific data of file .*
> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03a.s
> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03a.s
> new file mode 100644
> index 00000000000..f7f9ceb11f6
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03a.s
> @@ -0,0 +1 @@
> +       .attribute arch, "rv32i_zclsd"
> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03b.s
> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03b.s
> new file mode 100644
> index 00000000000..f18129dc55d
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-03b.s
> @@ -0,0 +1 @@
> +       .attribute arch, "rv32i_zcf"
> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.d
> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.d
> new file mode 100644
> index 00000000000..5445936df44
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.d
> @@ -0,0 +1,5 @@
> +#source: attr-merge-arch-failed-04a.s
> +#source: attr-merge-arch-failed-04b.s
> +#as: -mabi=ilp32
> +#ld: -r -m[riscv_choose_ilp32_emul]
> +#error_output: attr-merge-arch-failed-04.l
> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.l
> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.l
> new file mode 100644
> index 00000000000..930e03123e1
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04.l
> @@ -0,0 +1,2 @@
> +.*: zcmp' is incompatible with `d' and `c', or `zcd' extension
> +.*: failed to merge target specific data of file .*
> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04a.s
> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04a.s
> new file mode 100644
> index 00000000000..e79c25b7828
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04a.s
> @@ -0,0 +1 @@
> +       .attribute arch, "rv32ic"
> diff --git a/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04b.s
> b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04b.s
> new file mode 100644
> index 00000000000..c7468e4e072
> --- /dev/null
> +++ b/ld/testsuite/ld-riscv-elf/attr-merge-arch-failed-04b.s
> @@ -0,0 +1 @@
> +       .attribute arch, "rv32id_zcmp"
> diff --git a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
> b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
> index 8e26ccff10a..57f3139c9f6 100644
> --- a/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
> +++ b/ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp
> @@ -157,6 +157,10 @@ if [istarget "riscv*-*-*"] {
>      run_dump_test "attr-merge-arch-01"
>      run_dump_test "attr-merge-arch-02"
>      run_dump_test "attr-merge-arch-03"
> +    run_dump_test "attr-merge-arch-failed-01"
> +    run_dump_test "attr-merge-arch-failed-02"
> +    run_dump_test "attr-merge-arch-failed-03"
> +    run_dump_test "attr-merge-arch-failed-04"
>      run_dump_test "attr-merge-strict-align-01"
>      run_dump_test "attr-merge-strict-align-02"
>      run_dump_test "attr-merge-strict-align-03"
> --
> 2.54.0
>
>