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Base address of executables - weirdness?

DISCUSSION H. Peter Anvin 3 participants 5 messages Jun 6, 2006

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H. Peter Anvin

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I'm trying to track down an odd issue with klibc on ppc32.

Until recently, binaries linked with ld defaulted to a base address of 0x10000000+SIZEOF_HEADERS. However, recently I've gotten a couple of reports -- and I've been able to confirm this on my FC5 system -- that some versions of ld links at 0x01800000+SIZEOF_HEADERS. Needless to say, this is more than a bit confusing, *especially* since "ld -verbose" still reports:

    PROVIDE (__executable_start = 0x10000000); . = 0x10000000 +

SIZEOF_HEADERS;

... at the top of the linker script.

I'm rather baffled. Has anyone else seen this, and/or have any other explanation?

-hpa

#1 lore raw
Quoted 9 lines · H. Peter Anvin

I'm trying to track down an odd issue with klibc on ppc32.

Until recently, binaries linked with ld defaulted to a base address of 0x10000000+SIZEOF_HEADERS. However, recently I've gotten a couple of reports -- and I've been able to confirm this on my FC5 system -- that some versions of ld links at 0x01800000+SIZEOF_HEADERS. Needless to say, this is more than a bit confusing, *especially* since "ld -verbose" still reports:

Quoted 7 lines
     PROVIDE (__executable_start = 0x10000000); . = 0x10000000 +

SIZEOF_HEADERS;

... at the top of the linker script.

I'm rather baffled. Has anyone else seen this, and/or have any other explanation?

Googling "0x01800000 linux ppc" brings up some interesting but old hits.

However, I swear I saw someone suggest a patch last week that changed 0x10000000 to 0x01800000 somewhere, (vmlinux.lds ??) as a proposed cure for a bug. Sorry, I deleted it.

--linas

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#2 lore raw
Quoted 10 lines · Linas Vepstas
Quoted 9 lines · H. Peter Anvin

I'm trying to track down an odd issue with klibc on ppc32.

Until recently, binaries linked with ld defaulted to a base address of 0x10000000+SIZEOF_HEADERS. However, recently I've gotten a couple of reports -- and I've been able to confirm this on my FC5 system -- that some versions of ld links at 0x01800000+SIZEOF_HEADERS. Needless to say, this is more than a bit confusing, *especially* since "ld -verbose" still reports:

     PROVIDE (__executable_start = 0x10000000); . = 0x10000000 +

SIZEOF_HEADERS;

... at the top of the linker script.

Quoted 8 lines
Quoted 1 line

I'm rather baffled. Has anyone else seen this, and/or have any other explanation?

Googling "0x01800000 linux ppc" brings up some interesting but old hits.

However, I swear I saw someone suggest a patch last week that changed 0x10000000 to 0x01800000 somewhere, (vmlinux.lds ??) as a proposed cure for a bug. Sorry, I deleted it.

Well, it's worse than I previously surmised. I can't seem to find any combination of options which work on both affected and unaffected binutils. This is a real mess.

-hpa

#3 lore raw
In reply to H. Peter Anvin
Quoted 4 lines · H. Peter Anvin

Until recently, binaries linked with ld defaulted to a base address of 0x10000000+SIZEOF_HEADERS. However, recently I've gotten a couple of reports -- and I've been able to confirm this on my FC5 system -- that some versions of ld links at 0x01800000+SIZEOF_HEADERS.

You are probably using the wrong linker emulation. There are three emulations enabled when building binutils for ppc-linux, but only the elf32ppclinux emulation it the right one that uses 0x10000000 for the base address.

Andreas.

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Andreas Schwab, SuSE Labs, [email protected]
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."
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#4 lore raw
Quoted 9 lines · Andreas Schwab
Quoted 1 line · H. Peter Anvin

Until recently, binaries linked with ld defaulted to a base address of 0x10000000+SIZEOF_HEADERS. However, recently I've gotten a couple of reports -- and I've been able to confirm this on my FC5 system -- that some versions of ld links at 0x01800000+SIZEOF_HEADERS.

You are probably using the wrong linker emulation. There are three emulations enabled when building binutils for ppc-linux, but only the elf32ppclinux emulation it the right one that uses 0x10000000 for the base address.

Hm. Well, it's using the default one, but perhaps I should try to specify an explicit -m option. Sure enough, that did the trick.

THANKS!

-hpa