linux-kernel - Re: [PATCH v2 14/14] powerpc: Implement UACCESS validation on PPC32

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Message-ID: <20230622115659.GO4253@hirez.programming.kicks-ass.net>
Date:   Thu, 22 Jun 2023 13:56:59 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Sathvika Vasireddy <sv@...ux.ibm.com>,
        Naveen N Rao <naveen@...nel.org>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2 14/14] powerpc: Implement UACCESS validation on PPC32

On Thu, Jun 22, 2023 at 12:54:36PM +0200, Christophe Leroy wrote:

> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index f850ab892ad5..8ac5711a055f 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -218,6 +218,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
>  		"kthread_exit",
>  		"kunit_try_catch_throw",
>  		"lbug_with_loc",
> +		"longjmp",
>  		"machine_real_restart",
>  		"make_task_dead",
>  		"mpt_halt_firmware",
> @@ -230,7 +231,9 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
>  		"sev_es_terminate",
>  		"snp_abort",
>  		"start_kernel",
> +		"start_secondary_resume",
>  		"stop_this_cpu",
> +		"unrecoverable_exception",
>  		"usercopy_abort",
>  		"x86_64_start_kernel",
>  		"x86_64_start_reservations",

Someone went and changed all that in tip/objtool/core :-)

But perhaps, like the uaccess_safe_builtins[] array below, should we
start marking sections so we can remember where stuff comes from later?

> @@ -1335,6 +1338,8 @@ static const char *uaccess_safe_builtin[] = {
>  	"rep_stos_alternative",
>  	"rep_movs_alternative",
>  	"__copy_user_nocache",
> +	"__copy_tofrom_user",
> +	"__arch_clear_user",
>  	NULL
>  };

Do we want to rename the 'misc' sectino to 'x86' and start a 'ppc32'
section there?