linux-kernel - Re: [PATCH V2 8/9] tools/perf: Add support to find global register variables using find_data_type_global

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Message-ID: <05213684-d45b-4a6c-82ef-6ec7fd2653b2@csgroup.eu>
Date: Tue, 7 May 2024 10:03:02 +0000
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, "acme@...nel.org"
	<acme@...nel.org>, "jolsa@...nel.org" <jolsa@...nel.org>,
	"adrian.hunter@...el.com" <adrian.hunter@...el.com>, "irogers@...gle.com"
	<irogers@...gle.com>, "namhyung@...nel.org" <namhyung@...nel.org>,
	"segher@...nel.crashing.org" <segher@...nel.crashing.org>
CC: "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"maddy@...ux.ibm.com" <maddy@...ux.ibm.com>, "kjain@...ux.ibm.com"
	<kjain@...ux.ibm.com>, "disgoel@...ux.vnet.ibm.com"
	<disgoel@...ux.vnet.ibm.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "akanksha@...ux.ibm.com"
	<akanksha@...ux.ibm.com>
Subject: Re: [PATCH V2 8/9] tools/perf: Add support to find global register
 variables using find_data_type_global_reg



Le 06/05/2024 à 14:19, Athira Rajeev a écrit :
> There are cases where define a global register variable and associate it
> with a specified register. Example, in powerpc, two registers are
> defined to represent variable:
> 1. r13: represents local_paca
> register struct paca_struct *local_paca asm("r13");
> 
> 2. r1: represents stack_pointer
> register void *__stack_pointer asm("r1");

What about r2:

register struct task_struct *current asm ("r2");

> 
> These regs are present in dwarf debug as DW_OP_reg as part of variables
> in the cu_die (compile unit). These are not present in die search done
> in the list of nested scopes since these are global register variables.
>