Hi Richard,
Thanks for the reply, I completely forgot that most people were probably on
holidays ☺
I’ll try the irc channel as well.
Cheers,
Tamar
From: Richard Eisenberg
Sent: Friday, August 14, 2015 04:46
To: loneti...@gmail.com
Cc: GHC
Subject: Re: Linker questions
Hi Tamar,
I haven't a clue about any of this. But I didn't want your detailed email to go
without any response. Perhaps agitate a bit on #ghc at freenode to get some
attention? Also, be aware that many people are on holiday right now, and so
responses may be slower than at other times.
Sorry I can't be more helpful, but I definitely appreciate your looking into
this!
Richard
On Aug 11, 2015, at 3:43 PM, loneti...@gmail.com wrote:
Hi *,
I had a few questions about the linker I was hoping someone can help me with,
I'm pretty new to it so any insights would be appreciated.
1) Has to do with checkProddableBlock and #10672 and #10563
static void checkProddableBlock (ObjectCode *oc, void *addr, size_t size )
{
ProddableBlock* pb;
for (pb = oc->proddables; pb != NULL; pb = pb->next) {
char* s = (char*)(pb->start);
char* e = s + pb->size;
char* a = (char*)addr;
if (a >= s && (a+size) <= e) return;
}
barf("checkProddableBlock: invalid fixup in runtime linker: %p", addr);
}
>From what I have found, these errors seem to happen because oc->proddables is
>initially NULL,
the for loop is skipped. From what I can tell, this function is checking if
there's a "proddable"
that fits within the supplied address and size. So if there is no proddables to
begin with, should this
check just not be skipped and the callee of this call not use this ObjectCode
instead of erroring out?
2) The second question is about static int ocGetNames_PEi386 ( ObjectCode* oc )
I am getting a test failure because it is claiming that .eh_frame section is
misaligned.
This comes from this code:
if (kind != SECTIONKIND_OTHER && end >= start) {
if ((((size_t)(start)) % 4) != 0) {
errorBelch("Misaligned section %s: %p", (char*)secname, start);
stgFree(secname);
return 0;
}
Where start is defined as:
start = ((UChar*)(oc->image)) + sectab_i->PointerToRawData;
and oc->image is a memory location received by allocateImageAndTrampolines.
In the case of my test failure it is because the .eh_frame section seems to
begin at 0x30F
since oc->image will always be 4 aligned (so it doesn't really matter in the
check) it gives that error because PointerToRawData isn't aligned by 4.
So my question is would it not be better just to check the alignment flag in
the PE section header instead of checking the load address (which is always
going to aligned to 4?) and The file pointer to
the first page of the section within the COFF file to determine the alignment?
Like objdump and dumpbin do?
e.g.
9 .eh_frame 00000038 00000000 00000000 0000030f 2**2
CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
Is the output from objdump which correctly determines the alignment from the
section. From what I understand from the PE specification
the on disk address doesn't have to be aligned by 4:
"For object files, the value *should* be aligned on a 4-byte boundary for best
performance."
I'm wondering if we are incorrectly erroring out here, instead of using the
section and making sure we pad it to the alignment boundary.
Regards,
Tamar
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