[Lldb-commits] [PATCH] D118494: [lldb] Observe SG_READ_ONLY flag in MachO binaries

Tue Feb 8 16:25:15 PST 2022

kastiglione added inline comments.

================
Comment at: lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp:1436
     result |= ePermissionsReadable;
-  if (seg_cmd.initprot & VM_PROT_WRITE)
+  if ((seg_cmd.initprot & VM_PROT_WRITE) && !(seg_cmd.flags & SG_READ_ONLY))
     result |= ePermissionsWritable;
----------------
aprantl wrote:
> kastiglione wrote:
> > augusto2112 wrote:
> > > Could we add a new value in the enumeration? Something like ePermissionsLinkerWritable? As it is right now this would be dangerous for the existing file-cache optimization as we'd happily read pointers that are supposed to be fixed by the linker from the file-cache.
> > That works for me. I think we'd want `ePermissionsLoaderWritable`.
> That sounds good.
Some idle questions:

1. Some code turns permissions into a string, like `rw-` or `r-x`, but there's no string character for this "hybrid" writable flag.
2. Other code might make r/w/x assumptions, and have bugs because of this extra state?
3. Do any other binary file formats have this notion, or would this be forcing a Mach-O specific flag into a portable concept?

I haven't looked yet, but I'm thinking it would be good if there were some other set of flags this information could be stored in.

I'm also not even sure if `SG_READ_ONLY` should modify permissions. For such a segment, should the permissions say it's writable, and something else say "actually no it's not", or should the permissions say it's non-writable, and something else says "actually it is written to by the loader".

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D118494/new/

https://reviews.llvm.org/D118494