cregit-Linux how code gets into the kernel

Release 4.14 arch/um/os-Linux/skas/process.c

/*
 * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
 * Copyright (C) 2002- 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include <stdlib.h>
#include <unistd.h>
#include <sched.h>
#include <errno.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <asm/unistd.h>
#include <as-layout.h>
#include <init.h>
#include <kern_util.h>
#include <mem.h>
#include <os.h>
#include <ptrace_user.h>
#include <registers.h>
#include <skas.h>
#include <sysdep/stub.h>
#include <linux/threads.h>


int is_skas_winch(int pid, int fd, void *data) { return pid == getpgrp(); }

Contributors

PersonTokensPropCommitsCommitProp
Gennady Sharapov1885.71%133.33%
Al Viro29.52%133.33%
Jeff Dike14.76%133.33%
Total21100.00%3100.00%


static int ptrace_dump_regs(int pid) { unsigned long regs[MAX_REG_NR]; int i; if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0) return -errno; printk(UM_KERN_ERR "Stub registers -\n"); for (i = 0; i < ARRAY_SIZE(regs); i++) printk(UM_KERN_ERR "\t%d - %lx\n", i, regs[i]); return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Jeff Dike76100.00%2100.00%
Total76100.00%2100.00%

/* * Signals that are OK to receive in the stub - we'll just continue it. * SIGWINCH will happen when UML is inside a detached screen. */ #define STUB_SIG_MASK ((1 << SIGALRM) | (1 << SIGWINCH)) /* Signals that the stub will finish with - anything else is an error */ #define STUB_DONE_MASK (1 << SIGTRAP)
void wait_stub_done(int pid) { int n, status, err; while (1) { CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL)); if ((n < 0) || !WIFSTOPPED(status)) goto bad_wait; if (((1 << WSTOPSIG(status)) & STUB_SIG_MASK) == 0) break; err = ptrace(PTRACE_CONT, pid, 0, 0); if (err) { printk(UM_KERN_ERR "wait_stub_done : continue failed, " "errno = %d\n", errno); fatal_sigsegv(); } } if (((1 << WSTOPSIG(status)) & STUB_DONE_MASK) != 0) return; bad_wait: err = ptrace_dump_regs(pid); if (err) printk(UM_KERN_ERR "Failed to get registers from stub, " "errno = %d\n", -err); printk(UM_KERN_ERR "wait_stub_done : failed to wait for SIGTRAP, " "pid = %d, n = %d, errno = %d, status = 0x%x\n", pid, n, errno, status); fatal_sigsegv(); }

Contributors

PersonTokensPropCommitsCommitProp
Gennady Sharapov8350.92%116.67%
Jeff Dike7847.85%466.67%
Stanislaw W. Gruszka21.23%116.67%
Total163100.00%6100.00%

extern unsigned long current_stub_stack(void);
static void get_skas_faultinfo(int pid, struct faultinfo *fi, unsigned long *aux_fp_regs) { int err; err = get_fp_registers(pid, aux_fp_regs); if (err < 0) { printk(UM_KERN_ERR "save_fp_registers returned %d\n", err); fatal_sigsegv(); } err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV); if (err) { printk(UM_KERN_ERR "Failed to continue stub, pid = %d, " "errno = %d\n", pid, errno); fatal_sigsegv(); } wait_stub_done(pid); /* * faultinfo is prepared by the stub_segv_handler at start of * the stub stack page. We just have to copy it. */ memcpy(fi, (void *)current_stub_stack(), sizeof(*fi)); err = put_fp_registers(pid, aux_fp_regs); if (err < 0) { printk(UM_KERN_ERR "put_fp_registers returned %d\n", err); fatal_sigsegv(); } }

Contributors

PersonTokensPropCommitsCommitProp
Jeff Dike8562.96%342.86%
Gennady Sharapov4130.37%114.29%
Thomas Meyer85.93%228.57%
Américo Wang10.74%114.29%
Total135100.00%7100.00%


static void handle_segv(int pid, struct uml_pt_regs *regs, unsigned long *aux_fp_regs) { get_skas_faultinfo(pid, &regs->faultinfo, aux_fp_regs); segv(regs->faultinfo, 0, 1, NULL); }

Contributors

PersonTokensPropCommitsCommitProp
Gennady Sharapov3681.82%133.33%
Thomas Meyer715.91%133.33%
Jeff Dike12.27%133.33%
Total44100.00%3100.00%

/* * To use the same value of using_sysemu as the caller, ask it that value * (in local_using_sysemu */
static void handle_trap(int pid, struct uml_pt_regs *regs, int local_using_sysemu) { int err, status; if ((UPT_IP(regs) >= STUB_START) && (UPT_IP(regs) < STUB_END)) fatal_sigsegv(); if (!local_using_sysemu) { err = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_NR_OFFSET, __NR_getpid); if (err < 0) { printk(UM_KERN_ERR "handle_trap - nullifying syscall " "failed, errno = %d\n", errno); fatal_sigsegv(); } err = ptrace(PTRACE_SYSCALL, pid, 0, 0); if (err < 0) { printk(UM_KERN_ERR "handle_trap - continuing to end of " "syscall failed, errno = %d\n", errno); fatal_sigsegv(); } CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL)); if ((err < 0) || !WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP + 0x80)) { err = ptrace_dump_regs(pid); if (err) printk(UM_KERN_ERR "Failed to get registers " "from process, errno = %d\n", -err); printk(UM_KERN_ERR "handle_trap - failed to wait at " "end of syscall, errno = %d, status = %d\n", errno, status); fatal_sigsegv(); } } handle_syscall(regs); }

Contributors

PersonTokensPropCommitsCommitProp
Gennady Sharapov12762.87%112.50%
Jeff Dike7235.64%562.50%
Stanislaw W. Gruszka20.99%112.50%
Al Viro10.50%112.50%
Total202100.00%8100.00%

extern char __syscall_stub_start[]; /** * userspace_tramp() - userspace trampoline * @stack: pointer to the new userspace stack page, can be NULL, if? FIXME: * * The userspace trampoline is used to setup a new userspace process in start_userspace() after it was clone()'ed. * This function will run on a temporary stack page. * It ptrace()'es itself, then * Two pages are mapped into the userspace address space: * - STUB_CODE (with EXEC), which contains the skas stub code * - STUB_DATA (with R/W), which contains a data page that is used to transfer certain data between the UML userspace process and the UML kernel. * Also for the userspace process a SIGSEGV handler is installed to catch pagefaults in the userspace process. * And last the process stops itself to give control to the UML kernel for this userspace process. * * Return: Always zero, otherwise the current userspace process is ended with non null exit() call */
static int userspace_tramp(void *stack) { void *addr; int fd; unsigned long long offset; ptrace(PTRACE_TRACEME, 0, 0, 0); signal(SIGTERM, SIG_DFL); signal(SIGWINCH, SIG_IGN); /* * This has a pte, but it can't be mapped in with the usual * tlb_flush mechanism because this is part of that mechanism */ fd = phys_mapping(to_phys(__syscall_stub_start), &offset); addr = mmap64((void *) STUB_CODE, UM_KERN_PAGE_SIZE, PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset); if (addr == MAP_FAILED) { printk(UM_KERN_ERR "mapping mmap stub at 0x%lx failed, " "errno = %d\n", STUB_CODE, errno); exit(1); } if (stack != NULL) { fd = phys_mapping(to_phys(stack), &offset); addr = mmap((void *) STUB_DATA, UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_FIXED | MAP_SHARED, fd, offset); if (addr == MAP_FAILED) { printk(UM_KERN_ERR "mapping segfault stack " "at 0x%lx failed, errno = %d\n", STUB_DATA, errno); exit(1); } } if (stack != NULL) { struct sigaction sa; unsigned long v = STUB_CODE + (unsigned long) stub_segv_handler - (unsigned long) __syscall_stub_start; set_sigstack((void *) STUB_DATA, UM_KERN_PAGE_SIZE); sigemptyset(&sa.sa_mask); sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO; sa.sa_sigaction = (void *) v; sa.sa_restorer = NULL; if (sigaction(SIGSEGV, &sa, NULL) < 0) { printk(UM_KERN_ERR "userspace_tramp - setting SIGSEGV " "handler failed - errno = %d\n", errno); exit(1); } } kill(os_getpid(), SIGSTOP); return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Gennady Sharapov17057.82%17.69%
Jeff Dike10836.73%969.23%
Richard Weinberger72.38%17.69%
Lepton Wu62.04%17.69%
Al Viro31.02%17.69%
Total294100.00%13100.00%

int userspace_pid[NR_CPUS]; /** * start_userspace() - prepare a new userspace process * @stub_stack: pointer to the stub stack. Can be NULL, if? FIXME: * * Setups a new temporary stack page that is used while userspace_tramp() runs * Clones the kernel process into a new userspace process, with FDs only. * * Return: When positive: the process id of the new userspace process, * when negative: an error number. * FIXME: can PIDs become negative?! */
int start_userspace(unsigned long stub_stack) { void *stack; unsigned long sp; int pid, status, n, flags, err; /* setup a temporary stack page */ stack = mmap(NULL, UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (stack == MAP_FAILED) { err = -errno; printk(UM_KERN_ERR "start_userspace : mmap failed, " "errno = %d\n", errno); return err; } /* set stack pointer to the end of the stack page, so it can grow downwards */ sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *); flags = CLONE_FILES | SIGCHLD; /* clone into new userspace process */ pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack); if (pid < 0) { err = -errno; printk(UM_KERN_ERR "start_userspace : clone failed, " "errno = %d\n", errno); return err; } do { CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL)); if (n < 0) { err = -errno; printk(UM_KERN_ERR "start_userspace : wait failed, " "errno = %d\n", errno); goto out_kill; } } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM)); if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) { err = -EINVAL; printk(UM_KERN_ERR "start_userspace : expected SIGSTOP, got " "status = %d\n", status); goto out_kill; } if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL, (void *) PTRACE_O_TRACESYSGOOD) < 0) { err = -errno; printk(UM_KERN_ERR "start_userspace : PTRACE_OLDSETOPTIONS " "failed, errno = %d\n", errno); goto out_kill; } if (munmap(stack, UM_KERN_PAGE_SIZE) < 0) { err = -errno; printk(UM_KERN_ERR "start_userspace : munmap failed, " "errno = %d\n", errno); goto out_kill; } return pid; out_kill: os_kill_ptraced_process(pid, 1); return err; }

Contributors

PersonTokensPropCommitsCommitProp
Gennady Sharapov21966.57%112.50%
Jeff Dike10130.70%337.50%
Stanislaw W. Gruszka41.22%112.50%
Thomas Meyer30.91%112.50%
Richard Weinberger10.30%112.50%
Anton Ivanov10.30%112.50%
Total329100.00%8100.00%


void userspace(struct uml_pt_regs *regs, unsigned long *aux_fp_regs) { int err, status, op, pid = userspace_pid[0]; /* To prevent races if using_sysemu changes under us.*/ int local_using_sysemu; siginfo_t si; /* Handle any immediate reschedules or signals */ interrupt_end(); while (1) { /* * This can legitimately fail if the process loads a * bogus value into a segment register. It will * segfault and PTRACE_GETREGS will read that value * out of the process. However, PTRACE_SETREGS will * fail. In this case, there is nothing to do but * just kill the process. */ if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp)) { printk(UM_KERN_ERR "userspace - ptrace set regs " "failed, errno = %d\n", errno); fatal_sigsegv(); } if (put_fp_registers(pid, regs->fp)) { printk(UM_KERN_ERR "userspace - ptrace set fp regs " "failed, errno = %d\n", errno); fatal_sigsegv(); } /* Now we set local_using_sysemu to be used for one loop */ local_using_sysemu = get_using_sysemu(); op = SELECT_PTRACE_OPERATION(local_using_sysemu, singlestepping(NULL)); if (ptrace(op, pid, 0, 0)) { printk(UM_KERN_ERR "userspace - ptrace continue " "failed, op = %d, errno = %d\n", op, errno); fatal_sigsegv(); } CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL)); if (err < 0) { printk(UM_KERN_ERR "userspace - wait failed, " "errno = %d\n", errno); fatal_sigsegv(); } regs->is_user = 1; if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp)) { printk(UM_KERN_ERR "userspace - PTRACE_GETREGS failed, " "errno = %d\n", errno); fatal_sigsegv(); } if (get_fp_registers(pid, regs->fp)) { printk(UM_KERN_ERR "userspace - get_fp_registers failed, " "errno = %d\n", errno); fatal_sigsegv(); } UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */ if (WIFSTOPPED(status)) { int sig = WSTOPSIG(status); ptrace(PTRACE_GETSIGINFO, pid, 0, (struct siginfo *)&si); switch (sig) { case SIGSEGV: if (PTRACE_FULL_FAULTINFO) { get_skas_faultinfo(pid, &regs->faultinfo, aux_fp_regs); (*sig_info[SIGSEGV])(SIGSEGV, (struct siginfo *)&si, regs); } else handle_segv(pid, regs, aux_fp_regs); break; case SIGTRAP + 0x80: handle_trap(pid, regs, local_using_sysemu); break; case SIGTRAP: relay_signal(SIGTRAP, (struct siginfo *)&si, regs); break; case SIGALRM: break; case SIGIO: case SIGILL: case SIGBUS: case SIGFPE: case SIGWINCH: block_signals(); (*sig_info[sig])(sig, (struct siginfo *)&si, regs); unblock_signals(); break; default: printk(UM_KERN_ERR "userspace - child stopped " "with signal %d\n", sig); fatal_sigsegv(); } pid = userspace_pid[0]; interrupt_end(); /* Avoid -ERESTARTSYS handling in host */ if (PT_SYSCALL_NR_OFFSET != PT_SYSCALL_RET_OFFSET) PT_SYSCALL_NR(regs->gp) = -1; } } }

Contributors

PersonTokensPropCommitsCommitProp
Gennady Sharapov23750.64%15.56%
Jeff Dike10923.29%844.44%
Ingo van Lil398.33%15.56%
Thomas Meyer316.62%211.11%
Martin Pärtel245.13%15.56%
Richard Weinberger204.27%15.56%
Al Viro40.85%15.56%
Stanislaw W. Gruszka20.43%15.56%
Anton Ivanov10.21%15.56%
Paolo 'Blaisorblade' Giarrusso10.21%15.56%
Total468100.00%18100.00%

static unsigned long thread_regs[MAX_REG_NR]; static unsigned long thread_fp_regs[FP_SIZE];
static int __init init_thread_regs(void) { get_safe_registers(thread_regs, thread_fp_regs); /* Set parent's instruction pointer to start of clone-stub */ thread_regs[REGS_IP_INDEX] = STUB_CODE + (unsigned long) stub_clone_handler - (unsigned long) __syscall_stub_start; thread_regs[REGS_SP_INDEX] = STUB_DATA + UM_KERN_PAGE_SIZE - sizeof(void *); #ifdef __SIGNAL_FRAMESIZE thread_regs[REGS_SP_INDEX] -= __SIGNAL_FRAMESIZE; #endif return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Jeff Dike6496.97%375.00%
Ingo van Lil23.03%125.00%
Total66100.00%4100.00%

__initcall(init_thread_regs);
int copy_context_skas0(unsigned long new_stack, int pid) { int err; unsigned long current_stack = current_stub_stack(); struct stub_data *data = (struct stub_data *) current_stack; struct stub_data *child_data = (struct stub_data *) new_stack; unsigned long long new_offset; int new_fd = phys_mapping(to_phys((void *)new_stack), &new_offset); /* * prepare offset and fd of child's stack as argument for parent's * and child's mmap2 calls */ *data = ((struct stub_data) { .offset = MMAP_OFFSET(new_offset), .fd = new_fd }); err = ptrace_setregs(pid, thread_regs); if (err < 0) { err = -errno; printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_SETREGS " "failed, pid = %d, errno = %d\n", pid, -err); return err; } err = put_fp_registers(pid, thread_fp_regs); if (err < 0) { printk(UM_KERN_ERR "copy_context_skas0 : put_fp_registers " "failed, pid = %d, err = %d\n", pid, err); return err; } /* set a well known return code for detection of child write failure */ child_data->err = 12345678; /* * Wait, until parent has finished its work: read child's pid from * parent's stack, and check, if bad result. */ err = ptrace(PTRACE_CONT, pid, 0, 0); if (err) { err = -errno; printk(UM_KERN_ERR "Failed to continue new process, pid = %d, " "errno = %d\n", pid, errno); return err; } wait_stub_done(pid); pid = data->err; if (pid < 0) { printk(UM_KERN_ERR "copy_context_skas0 - stub-parent reports " "error %d\n", -pid); return pid; } /* * Wait, until child has finished too: read child's result from * child's stack and check it. */ wait_stub_done(pid); if (child_data->err != STUB_DATA) { printk(UM_KERN_ERR "copy_context_skas0 - stub-child reports " "error %ld\n", child_data->err); err = child_data->err; goto out_kill; } if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL, (void *)PTRACE_O_TRACESYSGOOD) < 0) { err = -errno; printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_OLDSETOPTIONS " "failed, errno = %d\n", errno); goto out_kill; } return pid; out_kill: os_kill_ptraced_process(pid, 1); return err; }

Contributors

PersonTokensPropCommitsCommitProp
Gennady Sharapov18756.84%112.50%
Jeff Dike11133.74%675.00%
Ingo van Lil319.42%112.50%
Total329100.00%8100.00%


void new_thread(void *stack, jmp_buf *buf, void (*handler)(void)) { (*buf)[0].JB_IP = (unsigned long) handler; (*buf)[0].JB_SP = (unsigned long) stack + UM_THREAD_SIZE - sizeof(void *); }

Contributors

PersonTokensPropCommitsCommitProp
Jeff Dike3454.84%266.67%
Gennady Sharapov2845.16%133.33%
Total62100.00%3100.00%

#define INIT_JMP_NEW_THREAD 0 #define INIT_JMP_CALLBACK 1 #define INIT_JMP_HALT 2 #define INIT_JMP_REBOOT 3
void switch_threads(jmp_buf *me, jmp_buf *you) { if (UML_SETJMP(me) == 0) UML_LONGJMP(you, 1); }

Contributors

PersonTokensPropCommitsCommitProp
Gennady Sharapov2275.86%133.33%
Jeff Dike724.14%266.67%
Total29100.00%3100.00%

static jmp_buf initial_jmpbuf; /* XXX Make these percpu */ static void (*cb_proc)(void *arg); static void *cb_arg; static jmp_buf *cb_back;
int start_idle_thread(void *stack, jmp_buf *switch_buf) { int n; set_handler(SIGWINCH); /* * Can't use UML_SETJMP or UML_LONGJMP here because they save * and restore signals, with the possible side-effect of * trying to handle any signals which came when they were * blocked, which can't be done on this stack. * Signals must be blocked when jumping back here and restored * after returning to the jumper. */ n = setjmp(initial_jmpbuf); switch (n) { case INIT_JMP_NEW_THREAD: (*switch_buf)[0].JB_IP = (unsigned long) uml_finishsetup; (*switch_buf)[0].JB_SP = (unsigned long) stack + UM_THREAD_SIZE - sizeof(void *); break; case INIT_JMP_CALLBACK: (*cb_proc)(cb_arg); longjmp(*cb_back, 1); break; case INIT_JMP_HALT: kmalloc_ok = 0; return 0; case INIT_JMP_REBOOT: kmalloc_ok = 0; return 1; default: printk(UM_KERN_ERR "Bad sigsetjmp return in " "start_idle_thread - %d\n", n); fatal_sigsegv(); } longjmp(*switch_buf, 1); }

Contributors

PersonTokensPropCommitsCommitProp
Gennady Sharapov8963.57%114.29%
Jeff Dike5035.71%571.43%
Thomas Meyer10.71%114.29%
Total140100.00%7100.00%


void initial_thread_cb_skas(void (*proc)(void *), void *arg) { jmp_buf here; cb_proc = proc; cb_arg = arg; cb_back = &here; block_signals(); if (UML_SETJMP(&here) == 0) UML_LONGJMP(&initial_jmpbuf, INIT_JMP_CALLBACK); unblock_signals(); cb_proc = NULL; cb_arg = NULL; cb_back = NULL; }

Contributors

PersonTokensPropCommitsCommitProp
Gennady Sharapov6692.96%133.33%
Jeff Dike57.04%266.67%
Total71100.00%3100.00%


void halt_skas(void) { block_signals(); UML_LONGJMP(&initial_jmpbuf, INIT_JMP_HALT); }

Contributors

PersonTokensPropCommitsCommitProp
Gennady Sharapov1688.89%133.33%
Jeff Dike211.11%266.67%
Total18100.00%3100.00%


void reboot_skas(void) { block_signals(); UML_LONGJMP(&initial_jmpbuf, INIT_JMP_REBOOT); }

Contributors

PersonTokensPropCommitsCommitProp
Gennady Sharapov1688.89%133.33%
Jeff Dike211.11%266.67%
Total18100.00%3100.00%


void __switch_mm(struct mm_id *mm_idp) { userspace_pid[0] = mm_idp->u.pid; }

Contributors

PersonTokensPropCommitsCommitProp
Gennady Sharapov2095.24%150.00%
Jeff Dike14.76%150.00%
Total21100.00%2100.00%


Overall Contributors

PersonTokensPropCommitsCommitProp
Gennady Sharapov145155.02%12.00%
Jeff Dike95636.25%2958.00%
Ingo van Lil803.03%12.00%
Thomas Meyer521.97%48.00%
Richard Weinberger311.18%36.00%
Martin Pärtel240.91%12.00%
Al Viro190.72%510.00%
Stanislaw W. Gruszka100.38%12.00%
Lepton Wu60.23%12.00%
Anton Ivanov40.15%12.00%
Nicolas Iooss20.08%12.00%
Américo Wang10.04%12.00%
Paolo 'Blaisorblade' Giarrusso10.04%12.00%
Total2637100.00%50100.00%
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