From: Ian Lance Taylor <iant@google.com>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: John Reiser <jreiser@bitwagon.com>, binutils@sourceware.org
Subject: Re: gold patch committed (Was: Re: Help needed to track down bug: linking Linux kernel with gold creates unbootable kernel)
Date: Fri, 23 Apr 2010 15:50:00 -0000 [thread overview]
Message-ID: <mcrbpdauq1u.fsf@dhcp-172-17-9-151.mtv.corp.google.com> (raw)
In-Reply-To: <v2q6dc9ffc81004230830r3b8872fas6eed55c296481dc1@mail.gmail.com> (H. J. Lu's message of "Fri\, 23 Apr 2010 08\:30\:11 -0700")
"H.J. Lu" <hjl.tools@gmail.com> writes:
> On Fri, Apr 23, 2010 at 8:16 AM, Ian Lance Taylor <iant@google.com> wrote:
>> "H.J. Lu" <hjl.tools@gmail.com> writes:
>>
>>> Program Headers:
>>> Type Offset VirtAddr PhysAddr
>>> FileSiz MemSiz Flags Align
>>> LOAD 0x0000000000001000 0x0000000000000000 0x0000000000000000
>>> 0x0000000000000001 0x0000000000000001 R E 1000
>>> LOAD 0x0000000000002000 0x0000000000004000 0x0000000000004000
>>> 0x0000000000002001 0x0000000000002001 RW 4000
>>
>> This looks right to me.
>>
>>
>>> I am not sure it is a good idea to have different p_align.
>>
>> Why not? How else can we communicate the information requested by the
>> programmer? A system which cares about p_align needs to look at the
>> p_align of each PT_LOAD header.
>
> You can't load the first segment with 0x1000 alignment. You
> need to load the first segment with the alignment of the second
> segment. Why does gold have to make life harder for loader?
The Linux kernel doesn't look at the p_align field, nor should it.
The p_align field is clearly irrelevant when loading an executable.
The glibc dynamic linker checks that the p_align field looks
plausible, but otherwise ignores it other than for a PT_TLS segment;
that seems appropriate since ld.so is restricted to what mmap does
anyhow. In general, it's hard for me to think of why any loader on a
virtual memory system would look at the p_align field. And it's hard
for to think of any non-virtual memory system that would support ELF
style shared libraries.
So I think you are raising a purely hypothetical concern.
On the other hand the p_align field does convey information about the
sections in that particular segment, and that seems reasonable to me.
Ian
next prev parent reply other threads:[~2010-04-23 15:50 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-09 19:25 Help needed to track down bug: linking Linux kernel with gold creates unbootable kernel Török Edwin
2010-04-09 22:24 ` Ian Lance Taylor
2010-04-09 22:52 ` Doug Kwan (關振德)
2010-04-10 12:52 ` Török Edwin
2010-04-11 18:25 ` John Reiser
2010-04-12 9:39 ` Török Edwin
2010-04-12 15:17 ` John Reiser
2010-04-12 18:52 ` Török Edwin
2010-04-12 20:49 ` John Reiser
2010-04-13 5:27 ` Ian Lance Taylor
2010-04-22 21:10 ` H.J. Lu
2010-04-22 21:21 ` H.J. Lu
2010-04-22 21:27 ` Suresh Siddha
2010-04-23 0:00 ` Ian Lance Taylor
2010-04-23 0:24 ` H.J. Lu
2010-04-23 1:21 ` Ian Lance Taylor
2010-04-23 1:46 ` H.J. Lu
2010-04-23 1:58 ` David Miller
2010-04-23 2:38 ` H.J. Lu
2010-04-23 3:05 ` Ian Lance Taylor
2010-04-23 4:27 ` H.J. Lu
2010-04-22 21:25 ` John Reiser
2010-04-23 4:49 ` gold patch committed (Was: Re: Help needed to track down bug: linking Linux kernel with gold creates unbootable kernel) Ian Lance Taylor
2010-04-23 12:44 ` H.J. Lu
2010-04-23 14:12 ` Ian Lance Taylor
2010-04-23 14:35 ` H.J. Lu
2010-04-23 14:43 ` Ian Lance Taylor
2010-04-23 14:47 ` H.J. Lu
2010-04-23 15:31 ` Ian Lance Taylor
2010-04-23 15:39 ` H.J. Lu
2010-04-23 14:44 ` H.J. Lu
2010-04-23 15:16 ` Ian Lance Taylor
2010-04-23 15:30 ` H.J. Lu
2010-04-23 15:50 ` Ian Lance Taylor [this message]
2010-04-23 17:57 ` H.J. Lu
2010-04-23 15:55 ` John Reiser
2010-04-23 14:40 ` John Reiser
2010-04-23 14:02 ` Török Edwin
2010-04-23 14:48 ` H.J. Lu
2010-04-23 14:51 ` Török Edwin
2010-04-23 23:30 ` Ian Lance Taylor
2010-04-24 7:29 ` Török Edwin
2010-04-22 23:57 ` Help needed to track down bug: linking Linux kernel with gold creates unbootable kernel Ian Lance Taylor
2010-04-12 17:48 ` Ian Lance Taylor
2010-04-12 18:04 ` Török Edwin
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