Rich Felker
feee98903c
this patch improves the correctness, simplicity, and size of cancellation-related code. modulo any small errors, it should now be completely conformant, safe, and resource-leak free. the notion of entering and exiting cancellation-point context has been completely eliminated and replaced with alternative syscall assembly code for cancellable syscalls. the assembly is responsible for setting up execution context information (stack pointer and address of the syscall instruction) which the cancellation signal handler can use to determine whether the interrupted code was in a cancellable state. these changes eliminate race conditions in the previous generation of cancellation handling code (whereby a cancellation request received just prior to the syscall would not be processed, leaving the syscall to block, potentially indefinitely), and remedy an issue where non-cancellable syscalls made from signal handlers became cancellable if the signal handler interrupted a cancellation point. x86_64 asm is untested and may need a second try to get it right.
61 lines
1.3 KiB
C
61 lines
1.3 KiB
C
#ifndef LIBC_H
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#define LIBC_H
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#include <stdlib.h>
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#include <stdio.h>
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struct __libc {
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int *(*errno_location)(void);
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void (*testcancel)(void);
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void (*lock)(volatile int *);
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void (*lockfile)(FILE *);
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void (*fork_handler)(int);
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int (*atexit)(void (*)(void));
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void (*fini)(void);
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void (*ldso_fini)(void);
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volatile int threads_minus_1;
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int ofl_lock;
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FILE *ofl_head;
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};
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#if 100*__GNUC__+__GNUC_MINOR__ >= 303 || defined(__PCC__) || defined(__TINYC__)
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extern struct __libc __libc __attribute__((visibility("hidden")));
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#define libc __libc
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#elif !defined(__PIC__)
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extern struct __libc __libc;
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#define libc __libc
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#else
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#define USE_LIBC_ACCESSOR
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extern struct __libc *__libc_loc(void) __attribute__((const));
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#define libc (*__libc_loc())
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#endif
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/* Designed to avoid any overhead in non-threaded processes */
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void __lock(volatile int *);
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void __lockfile(FILE *);
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#define LOCK(x) (libc.threads_minus_1 ? (__lock(x),1) : ((void)(x),1))
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#define UNLOCK(x) (*(x)=0)
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int __rsyscall(int, long, long, long, long, long, long);
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extern char **__environ;
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#define environ __environ
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#undef weak_alias
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#define weak_alias(old, new) \
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extern __typeof(old) new __attribute__((weak, alias(#old)))
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#undef LFS64_2
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//#define LFS64_2(x, y) weak_alias(x, y)
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#define LFS64_2(x, y) extern __typeof(x) y
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#undef LFS64
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#define LFS64(x) LFS64_2(x, x##64)
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#endif
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