From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: Fangrui Song <maskray@google.com>
Cc: binutils@sourceware.org
Subject: Re: [PATCH] aarch64: Allow PC-relative relocations against protected STT_FUNC
Date: Thu, 23 Jun 2022 09:00:01 +0100 [thread overview]
Message-ID: <YrQdgTqhVC+U6b2/@arm.com> (raw)
In-Reply-To: <20220602065038.3198997-1-maskray@google.com>
The 06/01/2022 23:50, Fangrui Song wrote:
> __attribute__((visibility("protected"))) void *foo() {
> return (void *)foo;
> }
>
> gcc -fpic -shared incorrectly fails with:
>
> relocation R_AARCH64_ADR_PREL_PG_HI21 against symbol `foo' which may bind externally can not be used when making a shared object; recompile with -fPIC
>
> Call _bfd_elf_symbol_refs_local_p with local_protected==true to suppress
> the error. The new behavior matches gold and ld.lld.
>
> Note: if some code tries to use direct access relocations to take the
> address of foo (likely due to -fno-pic), the pointer equality will
> break, but the error should be reported on that link.
This patch looks good to me.
Thanks.
> ---
> bfd/elfnn-aarch64.c | 2 +-
> ld/testsuite/ld-aarch64/aarch64-elf.exp | 1 +
> ld/testsuite/ld-aarch64/pcrel-protected.s | 13 +++++++++++++
> ld/testsuite/ld-aarch64/pcrel_pic_protected.d | 7 +++++++
> 4 files changed, 22 insertions(+), 1 deletion(-)
> create mode 100644 ld/testsuite/ld-aarch64/pcrel-protected.s
> create mode 100644 ld/testsuite/ld-aarch64/pcrel_pic_protected.d
>
> diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
> index cb316a928ef..2c8e3439d43 100644
> --- a/bfd/elfnn-aarch64.c
> +++ b/bfd/elfnn-aarch64.c
> @@ -5878,7 +5878,7 @@ elfNN_aarch64_final_link_relocate (reloc_howto_type *howto,
> if (bfd_link_pic (info)
> && (input_section->flags & SEC_ALLOC) != 0
> && (input_section->flags & SEC_READONLY) != 0
> - && !SYMBOL_REFERENCES_LOCAL (info, h))
> + && !_bfd_elf_symbol_refs_local_p (h, info, 1))
> {
> int howto_index = bfd_r_type - BFD_RELOC_AARCH64_RELOC_START;
>
> diff --git a/ld/testsuite/ld-aarch64/aarch64-elf.exp b/ld/testsuite/ld-aarch64/aarch64-elf.exp
> index 64476f111e0..565a67aa9aa 100644
> --- a/ld/testsuite/ld-aarch64/aarch64-elf.exp
> +++ b/ld/testsuite/ld-aarch64/aarch64-elf.exp
> @@ -248,6 +248,7 @@ run_dump_test_lp64 "local-addend-r"
> # test error handling on pcrel relocation for shared libraries.
> run_dump_test_lp64 "pcrel_pic_undefined"
> run_dump_test_lp64 "pcrel_pic_defined"
> +run_dump_test_lp64 "pcrel_pic_protected"
>
> run_dump_test "limit-b"
> run_dump_test "limit-bl"
> diff --git a/ld/testsuite/ld-aarch64/pcrel-protected.s b/ld/testsuite/ld-aarch64/pcrel-protected.s
> new file mode 100644
> index 00000000000..ce2a92851ad
> --- /dev/null
> +++ b/ld/testsuite/ld-aarch64/pcrel-protected.s
> @@ -0,0 +1,13 @@
> +.protected protected_a
> +.protected protected_b
> +.type protected_b, %object
> +.protected protected_c
> +.type protected_c, %function
> +
> +.text
> + adrp x0, protected_a
> + add x0, x0, :lo12:protected_a
> + adrp x0, protected_b
> + add x0, x0, :lo12:protected_b
> + adrp x0, protected_c
> + add x0, x0, :lo12:protected_c
> diff --git a/ld/testsuite/ld-aarch64/pcrel_pic_protected.d b/ld/testsuite/ld-aarch64/pcrel_pic_protected.d
> new file mode 100644
> index 00000000000..1b6f24cf2fb
> --- /dev/null
> +++ b/ld/testsuite/ld-aarch64/pcrel_pic_protected.d
> @@ -0,0 +1,7 @@
> +#name: PC-Rel relocation against protected
> +#source: pcrel-protected.s
> +#target: [check_shared_lib_support]
> +#ld: -shared -e0 --defsym protected_a=0x1000 --defsym protected_b=0x1010 --defsym protected_c=0x1020
> +#readelf: -r -W
> +#...
> +There are no relocations in this file.
> --
> 2.36.1.255.ge46751e96f-goog
>
prev parent reply other threads:[~2022-06-23 8:00 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-02 6:50 Fangrui Song
2022-06-22 18:02 ` Fangrui Song
2022-06-23 8:00 ` Szabolcs Nagy [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YrQdgTqhVC+U6b2/@arm.com \
--to=szabolcs.nagy@arm.com \
--cc=binutils@sourceware.org \
--cc=maskray@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).