i386: Add the clone3 wrapper

extern int clone3 (struct clone_args *__cl_args, size_t __size,
		   int (*__func) (void *__arg), void *__arg);

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

diff --git a/sysdeps/unix/sysv/linux/i386/clone3.S b/sysdeps/unix/sysv/linux/i386/clone3.S
new file mode 100644 (file)
index 0000000..bef3ce0
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/i386/clone3.S
@@ -0,0 +1,123 @@
+/* The clone3 syscall wrapper.  Linux/i386 version.
+   Copyright (C) 2021 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
+   <https://www.gnu.org/licenses/>.  */
+
+/* clone3() is even more special than fork() as it mucks with stacks
+   and invokes a function in the right context after its all over.  */
+
+#include <sysdep.h>
+
+/* 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 on stack from userland:
+   16(%esp)    arg
+   12(%esp)    func
+    8(%esp)    size
+    4(%esp)    cl_args
+     (%esp)    Return address
+
+   The kernel expects:
+   eax:                system call number
+   ebx:                cl_args
+   ecx:                size
+ */
+
+#define CL_ARGS        4
+#define SIZE   8
+#define FUNC   12
+#define ARG    16
+
+        .text
+ENTRY (__clone3)
+       /* Sanity check arguments.  */
+       movl    $-EINVAL, %eax
+       movl    CL_ARGS(%esp), %ecx     /* No NULL cl_args pointer.  */
+       testl   %ecx, %ecx
+       jz      SYSCALL_ERROR_LABEL
+       /* Save the function pointer in EDX which is preserved by the
+          system call.  */
+       movl    FUNC(%esp), %edx        /* No NULL function pointer.  */
+       testl   %edx, %edx
+       jz      SYSCALL_ERROR_LABEL
+
+       /* Save EBX and ESI.  */
+       pushl   %ebx
+       cfi_adjust_cfa_offset (4)
+       pushl   %esi
+       cfi_adjust_cfa_offset (4)
+
+       /* Save the function argument in ESI which is preserved by the
+          system call.  */
+       movl    (ARG + 8)(%esp), %esi
+
+       /* Put cl_args in EBX.  */
+       movl    %ecx, %ebx
+
+       /* Put size in ECX.  */
+       movl    (SIZE + 8)(%esp), %ecx
+
+       /* Do the system call.  */
+       movl    $SYS_ify(clone3), %eax
+
+       /* End FDE now, because in the child the unwind info will be
+          wrong.  */
+       cfi_endproc
+
+       int     $0x80
+       test    %eax, %eax
+       /* No need to restore EBX and ESI in child.  */
+       jz      L(thread_start)
+
+       /* Restore EBX and ESI in parent.  */
+       pop     %esi
+       pop     %ebx
+       jl      SYSCALL_ERROR_LABEL
+
+       ret
+
+L(thread_start):
+       cfi_startproc
+       /* Clearing frame pointer is insufficient, use CFI.  */
+       cfi_undefined (eip)
+       xorl    %ebp, %ebp      /* Terminate the stack frame.  */
+
+       /* Align stack to 16 bytes per the i386 psABI.  */
+       andl    $-16, %esp
+
+       /* The PUSH below will decrement stack pointer by 4 bytes.  */
+       subl    $12, %esp
+
+       /* Set up the argument for the function call.  */
+       pushl   %esi            /* Argument.  */
+       cfi_adjust_cfa_offset (4)
+       call    *%edx           /* Call function.  */
+
+       /* Call exit with return value from function call. */
+       movl    %eax, %ebx
+       movl    $SYS_ify(exit), %eax
+       ENTER_KERNEL
+       cfi_endproc
+
+       cfi_startproc
+PSEUDO_END (__clone3)
+
+libc_hidden_def (__clone3)
+weak_alias (__clone3, clone3)

diff --git a/sysdeps/unix/sysv/linux/i386/sysdep.h b/sysdeps/unix/sysv/linux/i386/sysdep.h
index 8680b49bf7b70c8748ddd98f975c50aa787cd5a4..3927a1a6e06d03dfdaa2428cf75be1cf46bf8c77 100644 (file)
--- a/sysdeps/unix/sysv/linux/i386/sysdep.h
+++ b/sysdeps/unix/sysv/linux/i386/sysdep.h
@@ -291,6 +291,8 @@ struct libc_do_syscall_args
 # define HAVE_TIME_VSYSCALL             "__vdso_time"
 # define HAVE_CLOCK_GETRES_VSYSCALL     "__vdso_clock_getres"
 
+# define HAVE_CLONE3_WAPPER            1
+
 # undef HAVE_INTERNAL_BRK_ADDR_SYMBOL
 # define HAVE_INTERNAL_BRK_ADDR_SYMBOL 1