14f0e4d0e2
Porting zsh found four defects in the kernel and one in the filesystem. None of them were about zsh; all of them had been there the whole time. **exec threw the environment away.** kernel/fs/exec.c wrote a single zero for envp with the comment "(no environment)" -- not yet, but ever, for every process. musl has been passing a perfectly good envp to execve (Linux 59, which SchOS answers) and it was never read. So $TERM was unset, $PATH was whatever each program invented, and a variable exported in a shell did not survive the exec meant to carry it. exec() takes an envp, sys_exec reads argument three, and schinit manifests grew an Environment key. The userland two-argument exec(path, argv) stays as a wrapper that passes null explicitly -- the raw stub is execve now, so a short caller cannot leave %rdx holding a stray pointer. **Which overflowed the kernel stack.** Three pointer arrays, ~1.8 KB, on a 4096-byte stack, under exec -> loaduvm -> readi -> SchFS -> btree. Pid 1 went down on the first exec. The canary caught it and named the process, which is what it is for. They live in one kalloc'd page now. **waitpid returned a bare -1** for both "no children" and "interrupted". musl reads [-4095,-1] as -errno, so userspace saw EPERM; zsh printed "wait failed: operation not permitted" and abandoned the rest of /etc/zsh/zshrc. -ECHILD and -EINTR now. Third time a bare -1 has cost real time -- on a system with no permission model, EPERM should be read as "a syscall returned -1". **NVMA was 64.** musl's allocator takes a mapping per size class and does not release them eagerly, so compinit ran out of slots and got -1, which is EPERM, which malloc turns into NULL, which zsh reports as "fatal error: out of memory" -- on a machine with 1000 MB free. 256 slots, and -ENOMEM. **And a small write to SchFS costs 58 ms.** 200 writes to one open file take 11.75 s; the same to /dev/null take 0.14 s. That is the design stated at the top of kmount.c -- one transaction group per operation, and a commit is two flushes and an uberblock -- not a bug. But compdump writes its digest with thousands of separate prints, so it takes minutes and looks like a hang. compinit -D, which skips the dump, finishes in 3.6 s. This one is a decision rather than a fix, so it is written up and left: /etc/zsh/zshrc keeps compinit switched off and explains exactly why, with the measurements. zsh runs as /bin/zsh and is the console shell. ZLE works -- arrow keys recall history through terminfo, $COLUMNS reads the real 160 because TIOCGWINSZ was fixed, colour and prompt expansion work, startup is 0.14 s. mksh keeps /bin/sh, so schinit's no-jobs fallback is a different program from the one that could have failed. Also fixed while here: AT_CLKTCK was the literal 100 and is USER_HZ; the extract rule in four ports could move a source tree inside itself when make re-ran it, which is how zsh's configure came to write modfile=zsh-5.9/... into config.modules and fail three steps later. schfs-check passes. Full writeup in docs/history/kernel.md section 14. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01VQ7Qx8E1q1M1bbCq8QLHS2
129 lines
2.4 KiB
ArmAsm
129 lines
2.4 KiB
ArmAsm
#include "syscall.h"
|
|
#include "traps.h"
|
|
|
|
#define SYSCALL(name) \
|
|
.global name; \
|
|
name: \
|
|
mov $SYS_ ## name, %rax; \
|
|
mov %rcx, %r10 ;\
|
|
syscall ;\
|
|
ret
|
|
|
|
SYSCALL(fork)
|
|
.global _xv6_exit
|
|
_xv6_exit:
|
|
mov $SYS_exit, %rax
|
|
mov %rcx, %r10
|
|
syscall
|
|
ret
|
|
SYSCALL(wait)
|
|
SYSCALL(pipe)
|
|
SYSCALL(read)
|
|
SYSCALL(write)
|
|
SYSCALL(close)
|
|
SYSCALL(kill)
|
|
/* The raw stub is execve: three arguments, the Linux shape. exec() is a C
|
|
wrapper in glue.c that passes a null environment, so the 2-argument callers
|
|
in cmd/ cannot leave %rdx holding whatever happened to be there. */
|
|
.global execve
|
|
execve:
|
|
mov $SYS_exec, %rax
|
|
mov %rcx, %r10
|
|
syscall
|
|
ret
|
|
SYSCALL(open)
|
|
SYSCALL(mknod)
|
|
SYSCALL(unlink)
|
|
SYSCALL(fstat)
|
|
SYSCALL(link)
|
|
SYSCALL(mkdir)
|
|
SYSCALL(chdir)
|
|
SYSCALL(dup)
|
|
SYSCALL(dup2)
|
|
SYSCALL(fcntl)
|
|
SYSCALL(getpid)
|
|
SYSCALL(sbrk)
|
|
SYSCALL(sleep)
|
|
SYSCALL(uptime)
|
|
SYSCALL(vga_sync)
|
|
SYSCALL(getmouse)
|
|
SYSCALL(lseek)
|
|
SYSCALL(reboot)
|
|
SYSCALL(shutdown)
|
|
SYSCALL(sigfillset)
|
|
SYSCALL(sigprocmask)
|
|
SYSCALL(sigwait)
|
|
SYSCALL(alarm)
|
|
SYSCALL(waitpid)
|
|
SYSCALL(setsid)
|
|
SYSCALL(mmap)
|
|
SYSCALL(munmap)
|
|
SYSCALL(delete)
|
|
SYSCALL(show)
|
|
SYSCALL(showstat)
|
|
SYSCALL(ftruncate)
|
|
SYSCALL(truncate)
|
|
SYSCALL(rename)
|
|
SYSCALL(symlink)
|
|
SYSCALL(readlink)
|
|
SYSCALL(getuid)
|
|
SYSCALL(geteuid)
|
|
SYSCALL(nanosleep)
|
|
SYSCALL(mprotect)
|
|
SYSCALL(ioctl)
|
|
SYSCALL(getcwd)
|
|
SYSCALL(arch_prctl)
|
|
SYSCALL(set_tid_address)
|
|
SYSCALL(set_robust_list)
|
|
SYSCALL(futex)
|
|
SYSCALL(clone)
|
|
SYSCALL(exit_group)
|
|
SYSCALL(wait4)
|
|
SYSCALL(getgid)
|
|
SYSCALL(getegid)
|
|
SYSCALL(umask)
|
|
SYSCALL(writev)
|
|
SYSCALL(readv)
|
|
SYSCALL(brk)
|
|
SYSCALL(prlimit)
|
|
SYSCALL(stat)
|
|
SYSCALL(lstat)
|
|
SYSCALL(access)
|
|
SYSCALL(openat)
|
|
SYSCALL(fchdir)
|
|
SYSCALL(enable_linux_abi)
|
|
SYSCALL(getrlimit)
|
|
SYSCALL(setuid)
|
|
SYSCALL(setgid)
|
|
SYSCALL(getsid)
|
|
SYSCALL(dup3)
|
|
SYSCALL(pipe2)
|
|
SYSCALL(clock_gettime)
|
|
SYSCALL(getppid)
|
|
SYSCALL(rt_sigaction)
|
|
SYSCALL(shmget)
|
|
SYSCALL(shmat)
|
|
SYSCALL(shmdt)
|
|
SYSCALL(socket)
|
|
SYSCALL(bind)
|
|
SYSCALL(listen)
|
|
SYSCALL(accept)
|
|
SYSCALL(accept4)
|
|
SYSCALL(connect)
|
|
SYSCALL(sendto)
|
|
SYSCALL(recvfrom)
|
|
SYSCALL(sockshutdown)
|
|
SYSCALL(socketpair)
|
|
SYSCALL(setsockopt)
|
|
SYSCALL(getsockopt)
|
|
SYSCALL(mount)
|
|
SYSCALL(getdents64)
|
|
|
|
// Attributes and the index over them (SchFS phase 5). setxattr/getxattr/
|
|
// removexattr are Linux's; schfs_index and schfs_query are native, because
|
|
// asking a filesystem a question has no Linux equivalent.
|
|
SYSCALL(setxattr)
|
|
SYSCALL(getxattr)
|
|
SYSCALL(removexattr)
|
|
SYSCALL(schfs_index)
|
|
SYSCALL(schfs_query)
|