Track transition from launch dyld to shared-cache dyld #4826
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On macOS, a process will be launched with /usr/lib/dyld (the dynamic linker) and the main binary by the kernel. The first thing the standalone dyld will do is call into the dyld in the shared cache image. This patch tracks the transition between the dyld's at the very beginning of process startup. In DynamicLoaderMacOS::NotifyBreakpointHit() there are two new cases handled: `dyld_image_dyld_moved` which is the launch /usr/lib/dyld indicating that it is about call into the shared cache dyld ane evict itself. lldb will remove the notification breakpoint it set, clear the binary image list entirely, get the notification function pointer value out of the dyld_all_image_infos struct (which is the notification fptr in the to-be-run shared-cache dyld) and put an address breakpoint there. `dyld_notify_adding` is then called by shared-cache dyld, and we detect this case by noticing that we have an empty binary image list, normally impossibe, and treating this as if we'd just started a process attach/launch. Differential Revision: https://reviews.llvm.org/D127247 rdar://84222158
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jasonmolenda
approved these changes
Jun 14, 2022
JDevlieghere
approved these changes
Jun 14, 2022
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On macOS, a process will be launched with /usr/lib/dyld (the
dynamic linker) and the main binary by the kernel. The
first thing the standalone dyld will do is call into the dyld
in the shared cache image. This patch tracks the transition
between the dyld's at the very beginning of process startup.
In DynamicLoaderMacOS::NotifyBreakpointHit() there are two new
cases handled:
dyld_image_dyld_movedwhich is the launch /usr/lib/dyld indicatingthat it is about call into the shared cache dyld ane evict itself.
lldb will remove the notification breakpoint it set, clear the binary
image list entirely, get the notification function pointer value out
of the dyld_all_image_infos struct (which is the notification fptr
in the to-be-run shared-cache dyld) and put an address breakpoint
there.
dyld_notify_addingis then called by shared-cache dyld, and wedetect this case by noticing that we have an empty binary image list,
normally impossibe, and treating this as if we'd just started a
process attach/launch.
Differential Revision: https://reviews.llvm.org/D127247
rdar://84222158