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([2804:1b3:a7c0:a9f4:4405:8c19:a65e:e640]) by smtp.gmail.com with ESMTPSA id 21-20020a9d0115000000b00655ca9a109bsm311182otu.36.2022.11.03.06.15.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 03 Nov 2022 06:15:40 -0700 (PDT) Message-ID: <1d4ce210-2b28-b061-9780-f643eaa80a27@linaro.org> Date: Thu, 3 Nov 2022 10:15:36 -0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.4.1 Subject: Re: [PATCH v2 4/9] aarch64: Add the clone3 wrapper Content-Language: en-US To: Szabolcs Nagy Cc: libc-alpha@sourceware.org, Christian Brauner References: <20220930192613.3491147-1-adhemerval.zanella@linaro.org> <20220930192613.3491147-5-adhemerval.zanella@linaro.org> From: Adhemerval Zanella Netto Organization: Linaro In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-12.9 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,KAM_SHORT,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,TXREP 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 02/11/22 09:12, Szabolcs Nagy wrote: > The 09/30/2022 16:26, Adhemerval Zanella via Libc-alpha wrote: >> It follow the internal signature: >> >> extern int clone3 (struct clone_args *__cl_args, size_t __size, >> int (*__func) (void *__arg), void *__arg); >> >> And x86_64 semantics to return EINVAL if either cl_args or func >> is NULL. The stack is 16-byte aligned prior executing func. > > "x86_64 semantics" sounds wrong: maybe this should be documented? > i'd expect 0 cl_args/func to be UB like in most posix apis. Right, I think it is worth to document the function semantic properly at least on its internal header (include/clone_internal.h). H.J also added a new clone3.h headers, which is not currently installed that I am inclined to just remove it from now. We might reinstate if/when we decide to provide the clone3 as an ABI. And returning EINVAL for 0 cl_args/func aligns with our exported clone interface, where EINVAL is also returned for 0 function argument. > > and aligning sp in the child fails if signals are allowed there > (pthreads does not allow signals now, direct callers might). > i dont know if that's a concert (or if unaligned stack is > something we should fix up in clone3). It was overlooked on initial x86_64 clone3 implementation as well. I think it better to just return EINVAL for unaligned stacks and avoid to change the stack pointer in the created thread. > >> >> Checked on aarch64-linux-gnu. >> --- >> sysdeps/unix/sysv/linux/aarch64/clone3.S | 90 ++++++++++++++++++++++++ >> sysdeps/unix/sysv/linux/aarch64/sysdep.h | 2 + >> 2 files changed, 92 insertions(+) >> create mode 100644 sysdeps/unix/sysv/linux/aarch64/clone3.S >> >> diff --git a/sysdeps/unix/sysv/linux/aarch64/clone3.S b/sysdeps/unix/sysv/linux/aarch64/clone3.S >> new file mode 100644 >> index 0000000000..dba93430eb >> --- /dev/null >> +++ b/sysdeps/unix/sysv/linux/aarch64/clone3.S >> @@ -0,0 +1,90 @@ >> +/* The clone3 syscall wrapper. Linux/aarch64 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: >> + x0: cl_args >> + x1: size >> + x2: func >> + x3: arg */ >> + >> + .text >> +ENTRY(__clone3) >> + PTR_ARG (0) >> + PTR_ARG (1) >> + PTR_ARG (3) >> + PTR_ARG (4) >> + /* Save args for the child. */ >> + mov x10, x0 /* cl_args */ >> + mov x11, x2 /* func */ >> + mov x12, x3 /* args */ >> + >> + /* Sanity check args. */ >> + mov x0, #-EINVAL >> + cbz x10, .Lsyscall_error /* No NULL cl_args pointer. */ >> + cbz x2, .Lsyscall_error /* No NULL function pointer. */ >> + >> + /* Do the system call, the kernel expects: >> + x8: system call number >> + x0: cl_args >> + x1: size */ >> + mov x0, x10 >> + mov x8, #SYS_ify(clone3) >> + svc 0x0 >> + >> + cmp x0, #0 >> + beq thread_start >> + blt .Lsyscall_error >> + RET >> +PSEUDO_END (__clone3) >> + >> + .align 4 >> + .type thread_start, %function >> +thread_start: >> + cfi_startproc >> + cfi_undefined (x30) >> + mov x29, 0 >> + >> + /* Align sp. */ >> + mov x0, sp >> + and x0, x0, -16 >> + mov sp, x0 >> + >> + /* Pick the function arg and execute. */ >> + mov x0, x12 >> + blr x11 >> + >> + /* We are done, pass the return value through x0. */ >> + mov x8, #SYS_ify(exit) >> + svc 0x0 >> + cfi_endproc >> + .size thread_start, .-thread_start >> + >> +libc_hidden_def (__clone3) >> +weak_alias (__clone3, clone3) >> diff --git a/sysdeps/unix/sysv/linux/aarch64/sysdep.h b/sysdeps/unix/sysv/linux/aarch64/sysdep.h >> index f1853e012f..42bb22f5e6 100644 >> --- a/sysdeps/unix/sysv/linux/aarch64/sysdep.h >> +++ b/sysdeps/unix/sysv/linux/aarch64/sysdep.h >> @@ -164,6 +164,8 @@ >> # define HAVE_CLOCK_GETTIME64_VSYSCALL "__kernel_clock_gettime" >> # define HAVE_GETTIMEOFDAY_VSYSCALL "__kernel_gettimeofday" >> >> +# define HAVE_CLONE3_WRAPPER 1 >> + >> # undef INTERNAL_SYSCALL_RAW >> # define INTERNAL_SYSCALL_RAW(name, nr, args...) \ >> ({ long _sys_result; \ >> -- >> 2.34.1 >>