695712 - ARM xptcstubs assembly symbols tweaks

Status: RESOLVED WONTFIX

(Core :: XPCOM, defect)

Description

[Mike Hommey [:glandium]]

The ARM xptcstubs symbols all end up in the .text section even with -ffunction-sections, and have a size of 0, which makes them invisible to e.g. valgrind.

Comment 1

[Mike Hommey [:glandium]]

Attachment: ARM xptcstubs assembly symbols tweaks

PoC. This will need update against bug 681602.

Comment 2

[Mike Hommey [:glandium]]

Forgot to mention: since individual stubs use "b" to jump to the SharedStub, they all need to be kept close to each other, because moving one of them too far away from the others can break everything. I think there's an actual bug in gold that is responsible for the breakage, though.

Comment 3

[Mike Hommey [:glandium]]

(In reply to Mike Hommey [:glandium] from comment #2)
> Forgot to mention: since individual stubs use "b" to jump to the SharedStub,
> they all need to be kept close to each other, because moving one of them too
> far away from the others can break everything. I think there's an actual bug
> in gold that is responsible for the breakage, though.

It actually looks like gold is doing the right thing. Maybe I was having a separate issue.

Comment 4

[Julian Seward [:jseward]]

It's not the lack of a size that confuses V; it's the lack of a type.
As it stands, these fns get listed as STT_NOTYPE and are ignored by V.
Similar comments apply to bug 695719.

Even without this patch or the one in bug 695719, valgrind rev 12248
reduces the number of non-identified libxul.so basic blocks from 41 out
of circa 85000 down to just 2.