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85 lines
3.4 KiB
ArmAsm
85 lines
3.4 KiB
ArmAsm
/* Assembly code template for system call stubs.
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Copyright (C) 2009-2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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/* The real guts of this work are in the macros defined in the
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machine- and kernel-specific sysdep.h header file. Cancellable syscalls
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should be implemented using C implementation with SYSCALL_CANCEL macro.
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Each system call's object is built by a rule in sysd-syscalls
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generated by make-syscalls.sh that #include's this file after
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defining a few macros:
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SYSCALL_NAME syscall name
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SYSCALL_NARGS number of arguments this call takes
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SYSCALL_SYMBOL primary symbol name
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SYSCALL_NOERRNO 1 to define a no-errno version (see below)
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SYSCALL_ERRVAL 1 to define an error-value version (see below)
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We used to simply pipe the correct three lines below through cpp into
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the assembler. The main reason to have this file instead is so that
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stub objects can be assembled with -g and get source line information
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that leads a user back to a source file and these fine comments. The
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average user otherwise has a hard time knowing which "syscall-like"
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functions in libc are plain stubs and which have nontrivial C wrappers.
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Some versions of the "plain" stub generation macros are more than a few
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instructions long and the untrained eye might not distinguish them from
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some compiled code that inexplicably lacks source line information. */
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#include <sysdep.h>
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/* This indirection is needed so that SYMBOL gets macro-expanded. */
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#define syscall_hidden_def(SYMBOL) hidden_def (SYMBOL)
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#define T_PSEUDO(SYMBOL, NAME, N) PSEUDO (SYMBOL, NAME, N)
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#define T_PSEUDO_NOERRNO(SYMBOL, NAME, N) PSEUDO_NOERRNO (SYMBOL, NAME, N)
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#define T_PSEUDO_ERRVAL(SYMBOL, NAME, N) PSEUDO_ERRVAL (SYMBOL, NAME, N)
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#define T_PSEUDO_END(SYMBOL) PSEUDO_END (SYMBOL)
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#define T_PSEUDO_END_NOERRNO(SYMBOL) PSEUDO_END_NOERRNO (SYMBOL)
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#define T_PSEUDO_END_ERRVAL(SYMBOL) PSEUDO_END_ERRVAL (SYMBOL)
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#if SYSCALL_NOERRNO
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/* This kind of system call stub never returns an error.
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We return the return value register to the caller unexamined. */
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T_PSEUDO_NOERRNO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
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ret_NOERRNO
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T_PSEUDO_END_NOERRNO (SYSCALL_SYMBOL)
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#elif SYSCALL_ERRVAL
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/* This kind of system call stub returns the errno code as its return
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value, or zero for success. We may massage the kernel's return value
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to meet that ABI, but we never set errno here. */
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T_PSEUDO_ERRVAL (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
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ret_ERRVAL
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T_PSEUDO_END_ERRVAL (SYSCALL_SYMBOL)
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#else
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/* This is a "normal" system call stub: if there is an error,
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it returns -1 and sets errno. */
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T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
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ret
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T_PSEUDO_END (SYSCALL_SYMBOL)
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#endif
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syscall_hidden_def (SYSCALL_SYMBOL)
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