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Re: [PATCH] powerpc: Change SDT argument constraint
- From: fche at redhat dot com (Frank Ch. Eigler)
- To: Segher Boessenkool <segher at kernel dot crashing dot org>
- Cc: Mark Wielaard <mark at klomp dot org>, Sandipan Das <sandipan at linux dot vnet dot ibm dot com>, systemtap at sourceware dot org, naveen dot n dot rao at linux dot vnet dot ibm dot com
- Date: Thu, 05 Oct 2017 11:58:48 -0400
- Subject: Re: [PATCH] powerpc: Change SDT argument constraint
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- References: <20171005090941.22701-1-sandipan@linux.vnet.ibm.com> <1507198583.9961.29.camel@klomp.org> <20171005123945.GU8421@gate.crashing.org>
segher wrote:
> [...]
>> > Arguments: -4@9 -4@.LANCHOR0+44@toc@l(8) -4@.LANCHOR0+52@toc@l(
>> > 7)
>> >
>> > The second and third argument shown above are both having
>> > operands which are pointers to static data anchors. Since
>> > these static anchors are not included in the symbol table,
>> > they cannot be resolved from the binary itself. So, such
>> > arguments cannot be read via their corresponding markers.
By the way, such local symbols would be saved rather dropped if the
assembler flags included -L. Then stap should be able to resolve them.
> [...]
> I wonder why only PowerPC is hitting this problem though?
Analogous problems hit other platforms too. Addressing mode
availability, register set sizes, or GOT-like policies seem to
affect the exact degree.
- FChE