[Lldb-commits] [lldb] [lldb] IRMemoryMap zero address mapping fix (PR #99045)

[Jason Molenda via lldb-commits]

jasonmolenda wrote:

Ah, but I see my misunderstanding as I look at what debugserver returns.  It uses "no permissions" to indicate a memory range that is unmapped -- 

```
 <  23> send packet: $qMemoryRegionInfo:0#44
 <  27> read packet: $start:0;size:100000000;#00
 <  31> send packet: $qMemoryRegionInfo:100000000#c5
 <  67> read packet: $start:100000000;size:4000;permissions:rx;dirty-pages:100000000;#00
 <  31> send packet: $qMemoryRegionInfo:100004000#c9
 <  57> read packet: $start:100004000;size:4000;permissions:r;dirty-pages:;#00
 <  31> send packet: $qMemoryRegionInfo:100008000#cd
 <  32> read packet: $start:100008000;size:404000;#00
 <  31> send packet: $qMemoryRegionInfo:10040c000#fc
 < 198> read packet: $start:10040c000;size:40000;permissions:rw;dirty-pages:10040c000,100410000,100414000,100418000,10041c000,100420000,100424000,100428000,10042c000,100430000,100434000,100438000,10043c000,100440000;#00
```

0x100008000-0x000000010040c000 is a free address range in this example, and what this loop should choose if it had to find an unused memory range.  That conflicts with the behavior that this PR started with originally, where no permissions were returned for any memory regions --- which looks like the way debugserver reports a free memory region.

(The low 4 GB segment at the start of my output above is the PAGEZERO empty segment of virtual address space on 64-bit darwin processes)

https://github.com/llvm/llvm-project/pull/99045