From: Florian Weimer <fweimer@redhat.com>
To: Szabolcs Nagy <Szabolcs.Nagy@arm.com>
Cc: GNU C Library <libc-alpha@sourceware.org>,
Binutils <binutils@sourceware.org>,
GCC Development <gcc@gcc.gnu.org>,
"gnu-gabi\@sourceware.org" <gnu-gabi@sourceware.org>,
nd <nd@arm.com>,
Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
Richard Earnshaw <Richard.Earnshaw@arm.com>,
Tejas Belagod <Tejas.Belagod@arm.com>,
Richard Sandiford <Richard.Sandiford@arm.com>,
Steve Ellcey <sellcey@marvell.com>,
Richard Henderson <richard.henderson@linaro.org>
Subject: Re: [AArch64 ELF ABI] Vector calls and lazy binding on AArch64
Date: Tue, 01 Jan 2019 00:00:00 -0000 [thread overview]
Message-ID: <87y32y34wi.fsf@oldenburg2.str.redhat.com> (raw)
In-Reply-To: <7be6eecc-9e36-c782-1c87-e608bb1b5678@arm.com> (Szabolcs Nagy's message of "Wed, 22 May 2019 14:42:05 +0000")
* Szabolcs Nagy:
> AAELF64: in the Symbol Table section add
>
> st_other Values
> The st_other member of a symbol table entry specifies the symbol's
> visibility in the lowest 2 bits. The top 6 bits are unused in the
> generic ELF ABI [SCO-ELF], and while there are no values reserved for
> processor-specific semantics, many other architectures have used these
> bits.
>
> The defined processor-specific st_other flag values are listed in
> Table 4-5-1.
>
> Table 4-5-1, Processor specific st_other flags
> +------------------------+------+---------------------+
> |Name | Mask | Comment |
> +------------------------+------+---------------------+
> |STO_AARCH64_VARIANT_PCS | 0x80 | The function |
> | | | associated with the |
> | | | symbol may follow a |
> | | | variant procedure |
> | | | call standard with |
> | | | different register |
> | | | usage convention. |
> +------------------------+------+---------------------+
>
> A symbol table entry that is marked with the STO_AARCH64_VARIANT_PCS
> flag set in its st_other field may be associated with a function that
> follows a variant procedure call standard with different register
> usage convention from the one defined in the base procedure call
> standard for the list of argument, caller-saved and callee-saved
> registers [AAPCS64]. The rules in the Call and Jump relocations
> section still apply to such functions, and if a subroutine is called
> via a symbol reference that is marked with STO_AARCH64_VARIANT_PCS
> then code that runs between the calling routine and called subroutine
> must preserve the contents of all registers except IP0, IP1 and the
> condition code flags [AAPCS64].
Can you clarify if there has to be a valid stack at this point which can
be used during the call transfer? What about the stack alignment
requirement?
Thanks,
Florian
next prev parent reply other threads:[~2019-05-22 15:06 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-01 0:00 Szabolcs Nagy
2019-01-01 0:00 ` Florian Weimer [this message]
2019-01-01 0:00 ` Szabolcs Nagy
2019-01-01 0:00 ` Florian Weimer
2019-01-01 0:00 ` Szabolcs Nagy
2019-01-01 0:00 ` Szabolcs Nagy
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