9b06c6070c
Upon successful completion, the execve() system call invokes exec_setregs() to initialize the registers of the initial thread of the newly executed process. What is weird is that when execve() returns, it still goes through the normal system call return path, clobbering the registers with the system call's return value (td->td_retval). Though this doesn't seem to be problematic for x86 most of the times (as the value of eax/rax doesn't matter upon startup), this can be pretty frustrating for architectures where function argument and return registers overlap (e.g., ARM). On these systems, exec_setregs() also needs to initialize td_retval. Even worse are architectures where cpu_set_syscall_retval() sets registers to values not derived from td_retval. On these architectures, there is no way cpu_set_syscall_retval() can set registers to the way it wants them to be upon the start of execution. To get rid of this madness, let sys_execve() return EJUSTRETURN. This will cause cpu_set_syscall_retval() to leave registers intact. This makes process execution easier to understand. It also eliminates the difference between execution of the initial process and successive ones. The initial call to sys_execve() is not performed through a system call context. Reviewed by: kib, jhibbits Differential Revision: https://reviews.freebsd.org/D13180
190 lines
5.3 KiB
C
190 lines
5.3 KiB
C
/*-
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* Copyright (c) 2015 Nuxi, https://nuxi.nl/
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/imgact.h>
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#include <sys/kernel.h>
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#include <sys/proc.h>
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#include <sys/sysent.h>
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#include <vm/vm.h>
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#include <vm/pmap.h>
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#include <machine/frame.h>
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#include <machine/pcb.h>
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#include <machine/vmparam.h>
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#include <compat/cloudabi/cloudabi_util.h>
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#include <compat/cloudabi64/cloudabi64_syscall.h>
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#include <compat/cloudabi64/cloudabi64_util.h>
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extern const char *cloudabi64_syscallnames[];
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extern struct sysent cloudabi64_sysent[];
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static void
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cloudabi64_proc_setregs(struct thread *td, struct image_params *imgp,
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unsigned long stack)
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{
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struct trapframe *regs;
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exec_setregs(td, imgp, stack);
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/*
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* The stack now contains a pointer to the TCB and the auxiliary
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* vector. Let x0 point to the auxiliary vector, and set
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* tpidr_el0 to the TCB.
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*/
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regs = td->td_frame;
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regs->tf_x[0] =
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stack + roundup(sizeof(cloudabi64_tcb_t), sizeof(register_t));
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(void)cpu_set_user_tls(td, (void *)stack);
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}
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static int
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cloudabi64_fetch_syscall_args(struct thread *td)
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{
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struct trapframe *frame;
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struct syscall_args *sa;
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int i;
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frame = td->td_frame;
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sa = &td->td_sa;
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/* Obtain system call number. */
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sa->code = frame->tf_x[8];
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if (sa->code >= CLOUDABI64_SYS_MAXSYSCALL)
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return (ENOSYS);
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sa->callp = &cloudabi64_sysent[sa->code];
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sa->narg = sa->callp->sy_narg;
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/* Fetch system call arguments. */
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for (i = 0; i < MAXARGS; i++)
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sa->args[i] = frame->tf_x[i];
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/* Default system call return values. */
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td->td_retval[0] = 0;
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td->td_retval[1] = frame->tf_x[1];
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return (0);
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}
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static void
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cloudabi64_set_syscall_retval(struct thread *td, int error)
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{
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struct trapframe *frame = td->td_frame;
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switch (error) {
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case 0:
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/* System call succeeded. */
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frame->tf_x[0] = td->td_retval[0];
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frame->tf_x[1] = td->td_retval[1];
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frame->tf_spsr &= ~PSR_C;
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break;
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case ERESTART:
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/* Restart system call. */
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frame->tf_elr -= 4;
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break;
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case EJUSTRETURN:
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break;
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default:
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/* System call returned an error. */
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frame->tf_x[0] = cloudabi_convert_errno(error);
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frame->tf_spsr |= PSR_C;
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break;
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}
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}
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static void
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cloudabi64_schedtail(struct thread *td)
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{
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struct trapframe *frame = td->td_frame;
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/*
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* Initial register values for processes returning from fork.
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* Make sure that we only set these values when forking, not
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* when creating a new thread.
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*/
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if ((td->td_pflags & TDP_FORKING) != 0) {
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frame->tf_x[0] = CLOUDABI_PROCESS_CHILD;
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frame->tf_x[1] = td->td_tid;
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}
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}
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int
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cloudabi64_thread_setregs(struct thread *td,
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const cloudabi64_threadattr_t *attr, uint64_t tcb)
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{
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struct trapframe *frame;
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stack_t stack;
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/* Perform standard register initialization. */
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stack.ss_sp = TO_PTR(attr->stack);
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stack.ss_size = attr->stack_len;
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cpu_set_upcall(td, TO_PTR(attr->entry_point), NULL, &stack);
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/*
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* Pass in the thread ID of the new thread and the argument
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* pointer provided by the parent thread in as arguments to the
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* entry point.
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*/
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frame = td->td_frame;
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frame->tf_x[0] = td->td_tid;
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frame->tf_x[1] = attr->argument;
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/* Set up TLS. */
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return (cpu_set_user_tls(td, (void *)tcb));
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}
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static struct sysentvec cloudabi64_elf_sysvec = {
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.sv_size = CLOUDABI64_SYS_MAXSYSCALL,
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.sv_table = cloudabi64_sysent,
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.sv_fixup = cloudabi64_fixup,
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.sv_name = "CloudABI ELF64",
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.sv_coredump = elf64_coredump,
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.sv_pagesize = PAGE_SIZE,
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.sv_minuser = VM_MIN_ADDRESS,
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.sv_maxuser = VM_MAXUSER_ADDRESS,
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.sv_stackprot = VM_PROT_READ | VM_PROT_WRITE,
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.sv_copyout_strings = cloudabi64_copyout_strings,
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.sv_setregs = cloudabi64_proc_setregs,
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.sv_flags = SV_ABI_CLOUDABI | SV_CAPSICUM | SV_LP64,
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.sv_set_syscall_retval = cloudabi64_set_syscall_retval,
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.sv_fetch_syscall_args = cloudabi64_fetch_syscall_args,
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.sv_syscallnames = cloudabi64_syscallnames,
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.sv_schedtail = cloudabi64_schedtail,
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};
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INIT_SYSENTVEC(elf_sysvec, &cloudabi64_elf_sysvec);
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Elf64_Brandinfo cloudabi64_brand = {
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.brand = ELFOSABI_CLOUDABI,
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.machine = EM_AARCH64,
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.sysvec = &cloudabi64_elf_sysvec,
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.flags = BI_CAN_EXEC_DYN | BI_BRAND_ONLY_STATIC,
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};
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