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Mon, 28 Nov 2022 16:38:22 +0000 (GMT) Message-ID: Date: Mon, 28 Nov 2022 10:38:22 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.1 Subject: Re: [PATCH v2 05/11] powerpc64: Add the clone3 wrapper Content-Language: en-US To: libc-alpha@sourceware.org, Adhemerval Zanella References: <20221104190112.2566409-1-adhemerval.zanella@linaro.org> <20221104190112.2566409-6-adhemerval.zanella@linaro.org> In-Reply-To: <20221104190112.2566409-6-adhemerval.zanella@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 4nXx8qahZ00M6lhkpsocIRXjs7157r8K X-Proofpoint-GUID: 4nXx8qahZ00M6lhkpsocIRXjs7157r8K Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.895,Hydra:6.0.545,FMLib:17.11.122.1 definitions=2022-11-28_13,2022-11-28_02,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 bulkscore=0 spamscore=0 phishscore=0 suspectscore=0 adultscore=0 lowpriorityscore=0 mlxscore=0 impostorscore=0 clxscore=1011 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2210170000 definitions=main-2211280119 X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Paul E Murphy via Libc-alpha Reply-To: Paul E Murphy Errors-To: libc-alpha-bounces+e=80x24.org@sourceware.org Sender: "Libc-alpha" On 11/4/22 2:01 PM, Adhemerval Zanella via Libc-alpha wrote: > It follows the internal signature: > > extern int clone3 (struct clone_args *__cl_args, size_t __size, > int (*__func) (void *__arg), void *__arg); > > The powerpc64 ABI requires an initial stackframe so the child can > store/restore the TOC. Iit is create prior calling clone3 by trivial nit, s/Iit/It/. > adjusting the stack size (since kernel will compute the stack as > stack plus size). > > Checked on powerpc64-linux-gnu (power8, kernel 6.0) and > powerpc64le-linux-gnu (power9, kernel 4.18). > --- > .../sysv/linux/powerpc/powerpc64/clone3.S | 152 ++++++++++++++++++ > sysdeps/unix/sysv/linux/powerpc/sysdep.h | 1 + > 2 files changed, 153 insertions(+) > create mode 100644 sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S > > diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S b/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S > new file mode 100644 > index 0000000000..0fe2fe91db > --- /dev/null > +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S > @@ -0,0 +1,152 @@ > +/* The clone3 syscall wrapper. Linux/powerpc64 version. > + Copyright (C) 2022 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 > + . */ > + > +#include > +#define _ERRNO_H 1 > +#include > + > +/* The userland implementation is: > + int clone3 (struct clone_args *cl_args, size_t size, > + int (*func)(void *arg), void *arg); > + > + the kernel entry is: > + int clone3 (struct clone_args *cl_args, size_t size); > + > + The parameters are passed in registers from userland: > + r3: cl_args > + r4: size > + r5: func > + r6: arg */ > + > + .text > +ENTRY(__clone3) > + CALL_MCOUNT 4 > + > + /* Sanity checks args. */ > + cmpdi cr0, r3, 0 > + cmpdi cr1, r5, 0 > + cror cr0*4+eq, cr1*4+eq, cr0*4+eq > + beq cr0,L(badargs) > + > + /* Save some regs in the "red zone". */ Is there reason to avoid explicitly stacking a frame in here? Also, does the red zone exist on ELFv1? > +#ifdef USE_PPC_SCV > + std r28, -24(r1) > + cfi_offset (r28, -24) > +#endif > + std r29, -16(r1) > + std r30, -8(r1) > + cfi_offset (r29, -16) > + cfi_offset (r30, -8) > + > + /* Save fn and args across syscall. */ trivial nit, s/fn/func/ s/args/arg/. > + mr r30, r5 /* Function in r30. */ > + mr r29, r6 /* Argument in r29. */ > + > + /* End FDE now, because in the child the unwind info will be > + wrong. */ > + cfi_endproc > + > + /* Setup a minimum stack fram for child. It needs to first calculate s/fram/frame/. > + the effective stack address, write the start NULL frame-pointer, > + and update the frame size in the input cl_args. */ > + ld r7, 40(r3) /* Load stack value. */ > + ld r8, 48(r3) /* Load stack_size value. */ > + li r10, 0 > + add r7, r7, r8 /* Calculate effective stack address. */ > + std r10, -FRAME_MIN_SIZE_PARM(r7) This is clearing the backchain pointer? Maybe a small comment here. > + addi r8, r8, -FRAME_MIN_SIZE_PARM > + std r8, 48(r3) > + > + /* Do the system call, the kernel expects: > + r0: system call numer > + r3: cl_args > + r4: size */ > + li r0, SYS_ify(clone3) > +#ifdef USE_PPC_SCV > + CHECK_SCV_SUPPORT r28 0f > + /* This is equivalent to DO_CALL_SCV, but we cannot use the macro here > + because it uses CFI directives and we just called cfi_endproc. */ > + mflr r9 > + std r9, FRAME_LR_SAVE(r1) > + .machine "push" > + .machine "power9" > + scv 0 > + .machine "pop" > + ld r9, FRAME_LR_SAVE(r1) > + mtlr r9 > + > + /* When using scv, error is indicated by negative r3. */ With scv an, an error is a value -4095 <= x < 0. This test should be more specific. > + cmpdi cr1, r3, 0 > + b 1f > +#endif > +0: DO_CALL_SC > + > + /* With sc, error is indicated by cr0.SO. */ > + cmpdi cr1, r3, 0 > + crandc cr1*4+eq, cr1*4+eq, cr0*4+so > + > +1: bne- cr1,L(parent) > + > + /* Child, load the function and arguments. */ > + std r2, FRAME_TOC_SAVE(r1) > + PPC64_LOAD_FUNCPTR r30 > + mr r3, r29 > + bctrl > + ld r2, FRAME_TOC_SAVE(r1) > + > + li r0, SYS_ify(exit) > + DO_CALL_SC Minor nit, this should also use scv if supported. > + /* We won't ever get here but provide a nop so that the linker > + will insert a toc adjusting stub if necessary. */ > + nop > + > +L(badargs): > + cfi_startproc > + li r3, EINVAL > + TAIL_CALL_SYSCALL_ERROR > + > +L(parent): > + /* Check if svc is available. */ s/svc/scv/. > + cmpdi cr1, r28, 0 > + > + /* Parent. Restore registers & return. */ > +#ifdef USE_PPC_SCV > + cfi_offset (r28, -24) > + ld r28, -24(r1) > + cfi_restore (r28) > +#endif > + cfi_offset (r29,-16) > + cfi_offset (r30,-8) > + ld r29, -16(r1) > + ld r30, -8(r1) > + cfi_restore (r29) > + cfi_restore (r30) > + > +#ifdef USE_PPC_SCV > + beq cr1, 0f > + RET_SCV > + b 1f > +#endif > +0: RET_SC > +1: TAIL_CALL_SYSCALL_ERROR > + > +PSEUDO_END (__clone3) > + > +libc_hidden_def (__clone3) > +weak_alias (__clone3, clone3) > diff --git a/sysdeps/unix/sysv/linux/powerpc/sysdep.h b/sysdeps/unix/sysv/linux/powerpc/sysdep.h > index 9e44818978..af63b3974b 100644 > --- a/sysdeps/unix/sysv/linux/powerpc/sysdep.h > +++ b/sysdeps/unix/sysv/linux/powerpc/sysdep.h > @@ -214,6 +214,7 @@ > #if defined(__PPC64__) || defined(__powerpc64__) > #define HAVE_CLOCK_GETRES64_VSYSCALL "__kernel_clock_getres" > #define HAVE_CLOCK_GETTIME64_VSYSCALL "__kernel_clock_gettime" > +#define HAVE_CLONE3_WRAPPER 1 > #else > #define HAVE_CLOCK_GETRES_VSYSCALL "__kernel_clock_getres" > #define HAVE_CLOCK_GETTIME_VSYSCALL "__kernel_clock_gettime"