[AArch64] Correctly pad out service request stubs when relocating. #8056
Conversation
|
@mxw, this addresses an issue where service request stubs were changing size during relocation. Theoretically the other platforms can have the same problem arise. It's probably not worth implementing this, though an assert might be prudent if there isn't one already. |
| srcAddrBegin = addr; | ||
| break; | ||
| } | ||
| } |
There was a problem hiding this comment.
I think this reads a bit better as a
auto const srcAddrBegin = [&] {
for (auto addr : env.meta.reusedStubs) {
if ((srcAddr >= addr) && (srcAddr < (addr + svcreq::stub_size()))) {
return addr;
}
}
return nullptr;
}();| while (src->Mask(ExceptionMask) == BRK) { | ||
| src = src->NextInstruction(); | ||
| env.rewrites.insert(src); | ||
| srcCount++; |
There was a problem hiding this comment.
Why don't we count the first one that we handle before this loop?
There was a problem hiding this comment.
srcCount and destCount are both set to 1 in the loop in relocateImpl() when the instruction is copied. Then these helper functions either leave it alone, rewrite that instruction, or extend that instruction. They update srcCount and destCount accordingly.
| } | ||
|
|
||
| // Pad out the remainder of the dest service request stub | ||
| auto const destAddrBegin = (srcAddrBegin == env.start) ? |
|
|
||
| // Pad out the remainder of the dest service request stub | ||
| auto const destAddrBegin = (srcAddrBegin == env.start) ? | ||
| destStart : env.rel.adjustedAddressAfter(srcAddrBegin); |
There was a problem hiding this comment.
question: Is destStart != env.rel.adjustedAddressAfter(srcAddrBegin) if srcAddrBegin == env.start?
There was a problem hiding this comment.
Yeah, because of the way the relocation mapping works, the first instruction does not get a mapping. This is behavior that I picked up from the other backends. The following is a snipped from relocateImpl() at line 679 of this version of the file:
if (srcAddr == env.start) {
/*
* For the start of the range, we only want to overwrite the "after"
* address (since the "before" address could belong to the previous
* tracelet, which could be being relocated to a completely different
* address. recordRange will do that for us, so just make sure we
* have the right address setup.
*/
destStart = destAddr;
} else {
env.rel.recordAddress(srcAddr, destAddr, 0);
}
There was a problem hiding this comment.
@mxw has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.
| while (src->Mask(ExceptionMask) == BRK) { | ||
| src = src->NextInstruction(); | ||
| env.rewrites.insert(src); | ||
| srcCount++; |
There was a problem hiding this comment.
srcCount and destCount are both set to 1 in the loop in relocateImpl() when the instruction is copied. Then these helper functions either leave it alone, rewrite that instruction, or extend that instruction. They update srcCount and destCount accordingly.
| } | ||
|
|
||
| // Pad out the remainder of the dest service request stub | ||
| auto const destAddrBegin = (srcAddrBegin == env.start) ? |
| srcAddrBegin = addr; | ||
| break; | ||
| } | ||
| } |
|
|
||
| // Pad out the remainder of the dest service request stub | ||
| auto const destAddrBegin = (srcAddrBegin == env.start) ? | ||
| destStart : env.rel.adjustedAddressAfter(srcAddrBegin); |
There was a problem hiding this comment.
Yeah, because of the way the relocation mapping works, the first instruction does not get a mapping. This is behavior that I picked up from the other backends. The following is a snipped from relocateImpl() at line 679 of this version of the file:
if (srcAddr == env.start) {
/*
* For the start of the range, we only want to overwrite the "after"
* address (since the "before" address could belong to the previous
* tracelet, which could be being relocated to a completely different
* address. recordRange will do that for us, so just make sure we
* have the right address setup.
*/
destStart = destAddr;
} else {
env.rel.recordAddress(srcAddr, destAddr, 0);
}
|
@dave-estes has updated the pull request. View: changes, changes since last import |
There was a problem hiding this comment.
@mxw has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.
There was a problem hiding this comment.
@mxw is landing this pull request. If you are a Facebook employee, you can view this diff on Phabricator.
No description provided.