Re: [lldb-dev] Duplicate use of "sp" register name on x86 targets
On Mon, 2021-09-06 at 13:23 +0200, Pavel Labath wrote: > On 25/08/2021 21:13, Michał Górny via lldb-dev wrote: > > Hi, > > > > While working on improving gdbserver compatibility, I've noticed that > > "sp" is used twice: > > > > 1. as an alt_name for esp/rsp register (giving full 32/64-bit stack > > pointer), > > > > 2. and as the name of sp pseudo-register (giving ESP/RSP truncated to 16 > > bits). > > > > FWICS the current lookup logic (at least for LLGS targets) means that 1. > > takes precedence, i.e. 'register read sp' and 'p $sp' will both resolve > > to RSP. The 16-bit SP is only visible via 'register read --all'. > > > > However, I'm wondering whether this is actually desirable. > > In particular, should 'sp' generic name take precedence over an actual > > 'sp' (pseudo-)register? > > > > Given that accessing the lower 16 bits of the stack pointer is pretty > useless, and I can think of several use cases for accessing the (full) > stack pointer in an architecture-agnostic way, I think that the current > precedence is right. Thanks, this makes sense to me. > > Which is not to say that the situation is ideal, but I'm not sure what > can we (short of travelling back in time) do about it. Maybe we can > provide some alias (sp_16, sp_86, ???), so that the register remains > addressable? > I was originally thinking of "_sp" but I suppose more specific names make more sense ;-). That said, I guess it can probably wait until someone actually sees a need for it. -- Best regards, Michał Górny ___ lldb-dev mailing list lldb-dev@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
Re: [lldb-dev] Duplicate use of "sp" register name on x86 targets
On 25/08/2021 21:13, Michał Górny via lldb-dev wrote: Hi, While working on improving gdbserver compatibility, I've noticed that "sp" is used twice: 1. as an alt_name for esp/rsp register (giving full 32/64-bit stack pointer), 2. and as the name of sp pseudo-register (giving ESP/RSP truncated to 16 bits). FWICS the current lookup logic (at least for LLGS targets) means that 1. takes precedence, i.e. 'register read sp' and 'p $sp' will both resolve to RSP. The 16-bit SP is only visible via 'register read --all'. However, I'm wondering whether this is actually desirable. In particular, should 'sp' generic name take precedence over an actual 'sp' (pseudo-)register? Given that accessing the lower 16 bits of the stack pointer is pretty useless, and I can think of several use cases for accessing the (full) stack pointer in an architecture-agnostic way, I think that the current precedence is right. Which is not to say that the situation is ideal, but I'm not sure what can we (short of travelling back in time) do about it. Maybe we can provide some alias (sp_16, sp_86, ???), so that the register remains addressable? pl ___ lldb-dev mailing list lldb-dev@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
[lldb-dev] Duplicate use of "sp" register name on x86 targets
Hi, While working on improving gdbserver compatibility, I've noticed that "sp" is used twice: 1. as an alt_name for esp/rsp register (giving full 32/64-bit stack pointer), 2. and as the name of sp pseudo-register (giving ESP/RSP truncated to 16 bits). FWICS the current lookup logic (at least for LLGS targets) means that 1. takes precedence, i.e. 'register read sp' and 'p $sp' will both resolve to RSP. The 16-bit SP is only visible via 'register read --all'. However, I'm wondering whether this is actually desirable. In particular, should 'sp' generic name take precedence over an actual 'sp' (pseudo-)register? -- Best regards, Michał Górny ___ lldb-dev mailing list lldb-dev@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
