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Sat, 11 Nov 2023 19:29:12 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Message-ID: <11c7df4f-5a19-4810-958b-1fbe1dd95017@FreeBSD.org> Date: Sat, 11 Nov 2023 11:29:11 -0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 01/24] gdb: don't handle i386 k registers as pseudo registers Content-Language: en-US To: Simon Marchi , gdb-patches@sourceware.org Cc: Simon Marchi References: <20231108051222.1275306-1-simon.marchi@polymtl.ca> <20231108051222.1275306-2-simon.marchi@polymtl.ca> From: John Baldwin In-Reply-To: <20231108051222.1275306-2-simon.marchi@polymtl.ca> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-4.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_PASS,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 11/7/23 9:00 PM, Simon Marchi wrote: > From: Simon Marchi > > I think that i386 k registers are raw registers, and therefore shouldn't > be handled in the various functions handling pseudo registers. > > What tipped me off is the code in i386_pseudo_register_read_into_value: > > else if (i386_k_regnum_p (gdbarch, regnum)) > { > regnum -= tdep->k0_regnum; > > /* Extract (always little endian). */ > status = regcache->raw_read (tdep->k0_regnum + regnum, raw_buf); > > We take regnum (the pseudo register number we want to read), subtract > k0_regnum, add k0_regnum, and pass the result to raw_read. So we would > end up calling raw_read with the same regnum as the function received > which is supposedly a pseudo register number. > > Other hints are: > > - The command `maint print raw-registers` shows the k registers. > - Printing $k0 doesn't cause i386_pseudo_register_read_into_value to be > called. > - There's code in i387-tdep.c to save/restore the k registers. Also, the bottom of i386_gdbarch_init (where all of the pseudo register numbers are allocated) doesn't allocate any pseudo register numbers for the k registers. I think this bit of code in i386_gdbarch_init is the definitive set of what counts as pseudo registers on i386/amd64. > Remove handling of the k registers from: > > - i386_pseudo_register_read_into_value > - i386_pseudo_register_write > - i386_ax_pseudo_register_collect Reviewed-by: John Baldwin -- John Baldwin