Re: [PATCH v2 07/21] nptl: powerpc: Fix Race conditions in pthread cancellation (BZ#12683)

[Tulio Magno Quites Machado Filho <tuliom at linux dot ibm dot com>]

Adhemerval Zanella <adhemerval.zanella@linaro.org> writes:

> This patches adds the powerpc64 modification required for the BZ#12683.
> It basically adds the required __pthread_get_pc function and a arch
> specific syscall_cancel implementation.
>
> The powerpc requires an arch-specific syscall_cancel because
> INTERNAL_SYSCALL_NCS adds a mfcr just after the sc instruction to get
> the CR0.SO bit information from kernel (which signals the error
> return status).  So for cancelled syscalls with side effects,
> __pthread_get_pc will point to mcfr and thus invalidating the checks
> on sigcancel_handler.
>
> Checked on powerpc64le-linux-gnu and powerpc-linux-gnu.
>
> 	[BZ #12683]
> 	* sysdeps/unix/sysv/linux/powerpc/syscall_cancel.S: New file.
> 	* sysdeps/unix/sysv/linux/powerpc/sysdep-cancel.h
> 	(__pthread_get_pc): New function.

This entry is outdated.  Both the file name and the function name need to be
updated.

> diff --git a/sysdeps/unix/sysv/linux/powerpc/syscall_cancel.S b/sysdeps/unix/sysv/linux/powerpc/syscall_cancel.S
> new file mode 100644
> index 0000000..2e56c72
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/powerpc/syscall_cancel.S
> @@ -0,0 +1,64 @@
> +/* Cancellable syscall wrapper.  Linux/powerpc version.
> +   Copyright (C) 2017 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <sysdep.h>
> +
> +/* long int [r3] __syscall_cancel_arch (int *cancelhandling [r3],
> +					long int nr   [r4],
> +					long int arg1 [r5],
> +					long int arg2 [r6],
> +					long int arg3 [r7],
> +					long int arg4 [r8],
> +					long int arg5 [r9],
> +					long int arg6 [r10])  */
> +
> +ENTRY (__syscall_cancel_arch)
> +
> +	.globl __syscall_cancel_arch_start
> +	.type  __syscall_cancel_arch_start,@function
> +__syscall_cancel_arch_start:
> +
> +	/* if (*cancelhandling & CANCELED_BITMASK)
> +	     __syscall_do_cancel()  */
> +	lwz     r0,0(r3)
> +	rldicl. r0,r0,62,63
> +	beq     1f
> +	b       __syscall_do_cancel

Should this be a Branch & Link?

-- 
Tulio Magno