From: Roland McGrath <roland@hack.frob.com>
To: Renlin Li <renlin.li@foss.arm.com>
Cc: libc-alpha@sourceware.org,
Marcus Shawcroft <Marcus.Shawcroft@arm.com>,
Richard Earnshaw <Richard.Earnshaw@arm.com>
Subject: Re: [GLIBC][AARCH64]Rewrite elf_machine_load_address using _DYNAMIC symbol
Date: Fri, 04 Nov 2016 21:24:00 -0000 [thread overview]
Message-ID: <20161104212440.A23F42C3AD8@topped-with-meat.com> (raw)
In-Reply-To: Renlin Li's message of Friday, 4 November 2016 09:42:23 +0000 <581C57FF.2090901@foss.arm.com>
On many or perhaps all machines, elf_machine_load_address could now be
implemented purely in C by using a link-time trick.
In C, just:
static inline ElfW(Addr) __attribute__ ((unused))
elf_machine_load_address (void)
{
extern const char _BASE[] __attribute__ ((visibility ("hidden")));
return (ElfW(Addr)) _BASE;
}
Then add a trivial input linker script to the ld.so link:
PROVIDE_HIDDEN(_BASE = 0);
I know this works for x86_64 and aarch64, and does not require a load.
(On x86_64 it's a single lea; on aarch64 it's a single adr+add pair.)
next prev parent reply other threads:[~2016-11-04 21:24 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-04 9:42 Renlin Li
2016-11-04 21:24 ` Roland McGrath [this message]
2016-11-07 15:15 ` Szabolcs Nagy
2016-11-07 15:23 ` Szabolcs Nagy
2016-11-07 15:52 ` Szabolcs Nagy
2016-11-09 19:06 ` Maciej W. Rozycki
2016-11-08 21:28 ` Roland McGrath
2016-11-09 14:48 ` Szabolcs Nagy
2016-11-09 22:02 ` Roland McGrath
2017-10-17 15:41 ` Szabolcs Nagy
2017-10-17 16:28 ` Szabolcs Nagy
2017-10-18 10:32 ` Renlin Li
2017-10-18 16:12 ` Szabolcs Nagy
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