Mercurial > hg > nginx
view src/os/unix/rfork_thread.S @ 5356:acd51b0f6fd4
Disable symlinks: use O_PATH to open path components.
It was introduced in Linux 2.6.39, glibc 2.14 and allows to obtain
file descriptors without actually opening files. Thus made it possible
to traverse path with openat() syscalls without the need to have read
permissions for path components. It is effectively emulates O_SEARCH
which is missing on Linux.
O_PATH is used in combination with O_RDONLY. The last one is ignored
if O_PATH is used, but it allows nginx to not fail when it was built on
modern system (i.e. glibc 2.14+) and run with a kernel older than 2.6.39.
Then O_PATH is unknown to the kernel and ignored, while O_RDONLY is used.
Sadly, fstat() is not working with O_PATH descriptors till Linux 3.6.
As a workaround we fallback to fstatat() with the AT_EMPTY_PATH flag
that was introduced at the same time as O_PATH.
author | Valentin Bartenev <vbart@nginx.com> |
---|---|
date | Mon, 02 Sep 2013 08:07:59 +0400 |
parents | d620f497c50f |
children |
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/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #include <sys/syscall.h> #include <machine/asm.h> /* * rfork_thread(3) - rfork_thread(flags, stack, func, arg); */ #define KERNCALL int $0x80 ENTRY(rfork_thread) push %ebp mov %esp, %ebp push %esi mov 12(%ebp), %esi # the thread stack address sub $4, %esi mov 20(%ebp), %eax # the thread argument mov %eax, (%esi) sub $4, %esi mov 16(%ebp), %eax # the thread start address mov %eax, (%esi) push 8(%ebp) # rfork(2) flags push $0 mov $SYS_rfork, %eax KERNCALL jc error cmp $0, %edx jne child parent: add $8, %esp pop %esi leave ret child: mov %esi, %esp pop %eax call *%eax # call a thread start address ... add $4, %esp push %eax push $0 mov $SYS_exit, %eax # ... and exit(2) after a thread would return KERNCALL error: add $8, %esp pop %esi leave PIC_PROLOGUE /* libc's cerror: jmp PIC_PLT(HIDENAME(cerror)) */ push %eax call PIC_PLT(CNAME(__error)) pop %ecx PIC_EPILOGUE mov %ecx, (%eax) mov $-1, %eax mov $-1, %edx ret