On Mon, 8 Jan 2024 at 12:18, Dirk Hohndel via subsurface
<[email protected]> wrote:
>
On Jan 8, 2024, at 11:15, Berthold Stoeger wrote:
> >
> > If all else fails, you could disassemble qmlmanager.ccc.o. as such:
> >
> > objdump -d
> > ./mobile-widgets/CMakeFiles/subsurface_mobile.dir/qmlmanager.cpp.o\
"objdump -d" is horrible at disassembly.
For some unfathomable reason, it doesn't look at relocation
information, so when it disassembles any instruction with relocations,
the end result is garbage.
And no, adding "-r" to make it show relocation information isn't much
better. The disassembly is still garbage, but there will now be an
extra line that basically says "if I wasn't showing you garbage, I
would use this line to tell you what the garbage should have been".
So then you can - manually - use that relocation information to show
what the disassembly should have been.
> That's what I did.
>
> Sorry for the LONG email :)
>
> 0000000000005d38 <QMLManager::~QMLManager()>:
> 5d38: a9bd57f6 stp x22, x21, [sp, #-48]!
> 5d3c: a9014ff4 stp x20, x19, [sp, #16]
> 5d40: a9027bfd stp x29, x30, [sp, #32]
> 5d44: 910083fd add x29, sp, #32
> 5d48: aa0003f3 mov x19, x0
> 5d4c: 90000008 adrp x8, 0x5000 <QMLManager::~QMLManager()+0x14>
> 5d50: f9400108 ldr x8, [x8]
> 5d54: 91004108 add x8, x8, #16
> 5d58: f9000008 str x8, [x0]
> 5d5c: 39442008 ldrb w8, [x0, #264]
> 5d60: 34000068 cbz w8, 0x5d6c <QMLManager::~QMLManager()+0x34>
> 5d64: 9103e260 add x0, x19, #248
> 5d68: 94000000 bl 0x5d68 <QMLManager::~QMLManager()+0x30>
> 5d6c: 90000008 adrp x8, 0x5000 <QMLManager::~QMLManager()+0x34>
> 5d70: f900011f str xzr, [x8]
> 5d74: 91044260 add x0, x19, #272
> 5d78: 94000000 bl 0x5d78 <QMLManager::~QMLManager()+0x40>
> 5d7c: 9103e260 add x0, x19, #248
> 5d80: 94000000 bl 0x5d80 <QMLManager::~QMLManager()+0x48>
> 5d84: f9407a60 ldr x0, [x19, #240]
> 5d88: b9400008 ldr w8, [x0]
Well, that
> 5d7c: 9103e260 add x0, x19, #248
is the call chain result from here:
8 Subsurface-mobile 0x000000010027589c
QMLManager::~QMLManager() + 68 (qmlmanager.cpp:608)
but that's really just the return point from that
> 5d78: 94000000 bl 0x5d78 <QMLManager::~QMLManager()+0x40>
and that's very much an example of the whole "objdump is showing
garbage". That function isn't calling itself, but that's what objdump
-d shows, because it doesn't look at the reloc info.
Anyway, I think this has probably been compiled with some sanitizer.
With "-r" to objdump, at least we'd see what the call target for that
"bl" instruction is, which might give some clue.
Linus
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