From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: Fangrui Song <maskray@google.com>,
libc-alpha@sourceware.org, Darius Rad <darius@bluespec.com>,
Palmer Dabbelt <palmer@dabbelt.com>
Subject: Re: [PATCH] riscv: Fix incorrect jal with HIDDEN_JUMPTARGET
Date: Thu, 28 Oct 2021 10:31:52 -0300 [thread overview]
Message-ID: <649b2178-45d0-f9db-f672-66af0eed62e9@linaro.org> (raw)
In-Reply-To: <20211028065019.3247061-1-maskray@google.com>
On 28/10/2021 03:50, Fangrui Song wrote:
> A non-local STV_DEFAULT defined symbol is by default preemptible in a
> shared object. j/jal cannot target a preemptible symbol. On other
> architectures, such a jump instruction either causes PLT [BZ #18822], or
> if short-ranged, sometimes rejected by the linker (but not by GNU ld's
> riscv port [ld PR/28509]).
>
> Use HIDDEN_JUMPTARGET to target a non-preemptible symbol instead.
>
> With this patch, ld.so and libc.so can be linked with LLD if source
> files are compiled/assembled with -mno-relax/-Wa,-mno-relax.
LGTM, thanks. I am testing a patch similar to this locally to make ldd
build glibc.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> ---
> sysdeps/riscv/setjmp.S | 2 +-
> sysdeps/unix/sysv/linux/riscv/setcontext.S | 5 +++--
> 2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/sysdeps/riscv/setjmp.S b/sysdeps/riscv/setjmp.S
> index 0b92016b31..bec7ff80f4 100644
> --- a/sysdeps/riscv/setjmp.S
> +++ b/sysdeps/riscv/setjmp.S
> @@ -21,7 +21,7 @@
>
> ENTRY (_setjmp)
> li a1, 0
> - j __sigsetjmp
> + j HIDDEN_JUMPTARGET (__sigsetjmp)
> END (_setjmp)
> ENTRY (setjmp)
> li a1, 1
> diff --git a/sysdeps/unix/sysv/linux/riscv/setcontext.S b/sysdeps/unix/sysv/linux/riscv/setcontext.S
> index 9510518750..e44a68aad4 100644
> --- a/sysdeps/unix/sysv/linux/riscv/setcontext.S
> +++ b/sysdeps/unix/sysv/linux/riscv/setcontext.S
> @@ -95,6 +95,7 @@ LEAF (__setcontext)
> 99: j __syscall_error
>
> END (__setcontext)
> +libc_hidden_def (__setcontext)
> weak_alias (__setcontext, setcontext)
>
> LEAF (__start_context)
> @@ -108,7 +109,7 @@ LEAF (__start_context)
> /* Invoke subsequent context if present, else exit(0). */
> mv a0, s2
> beqz s2, 1f
> - jal __setcontext
> -1: j exit
> + jal HIDDEN_JUMPTARGET (__setcontext)
> +1: j HIDDEN_JUMPTARGET (exit)
>
> END (__start_context)
>
next prev parent reply other threads:[~2021-10-28 13:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-28 6:50 Fangrui Song
2021-10-28 13:31 ` Adhemerval Zanella [this message]
2021-10-28 18:05 ` Palmer Dabbelt
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