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In D130985#3693453 <https://reviews.llvm.org/D130985#3693453>, @DavidSpickett
wrote:
> Tell me if I understand the strategy.
>
> If you're on arm64 but the process is actually arm32 and you ask for the
> general registers, you'll get back something with size < the size you expect
> for the 64 bit register set.
> If you're on arm32 then you always assume that the architecture is the host
> architecture (since there's no backward compatibility mode to worry about).
> (though see my comment about potential cross arch shenanigans)
>
> Ditto for x86_64 and i386.
>
> If the architecture doesn't have a 32/64 split then assume host architecture
> (as you did for s390x).
>
> And ppc64 we don't support a ppc32 so again use the host (and maybe ppc64
> doesn't have a backward compatibility mode in linux anyway).
>
> And you're looking at the size of the register context, not the number of
> registers or their names or whatever. So even for something like RISCV vs
> RISCV64 where the number and names of registers is the same, the *size*
> changes with the bitness (xlen I think they call it) so it would still work.
That is correct. I couldn't have said it better myself. :)
> If so, sounds good to me.
================
Comment at:
lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm.cpp:792
RegisterValue &value) {
// PTRACE_PEEKUSER don't work in the aarch64 linux kernel used on android
// devices (always return "Bad address"). To avoid using PTRACE_PEEKUSER we
----------------
This one.
================
Comment at:
lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_arm.cpp:844
return NativeRegisterContextLinux::ReadGPR();
#else // __aarch64__
struct iovec ioVec;
----------------
DavidSpickett wrote:
> Is this a problem? First time I'm seeing such code I thought to debug arm32
> on arm64 you just had to use an arm32 lldb-server binary.
>
> Host architecture would be arm64 if `__aarch64__` was defined, right? Same
> thing if I took an arm32 lldb-server binary and ran it on arm64, host is
> arm64.
>
> Or is this not a problem. This architecture detection is a last resort so not
> getting a corner case right might be fine.
Well.. it's definitely not a problem here. I think this is related to the
problem on described on line 792 (they were introduced in the same commit --
e85e6021f040e399203883a78c53b1617053e141), although it may not be relevant
anymore.
Generally speaking there can be some differences in the 32-bit codepaths when
speaking to 32 or 64-bit kernels. For example, one can use PTRACE_SINGLESTEP
for debugging arm(32) binaries on 64-bit kernels, even though that
functionality would is not present on real 32-bit kernels.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D130985/new/
https://reviews.llvm.org/D130985
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