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git://sourceware.org/git/newlib-cygwin.git
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9b51beeb2a
Previously, __internal_syscall() compiled into asm-code that unconditionally
sets the syscall argument registers a0 to a5.
For example, the instruction sequence for a exit syscall looked like
this:
li a0, 1 # in ther caller of exit()
# ... # in newlib:
li a1, 0 # unused arguments
li a2, 0
li a3, 0
li a4, 0
li a5, 0
li a7, 93 # exit syscall number
(i.e. the binary contains then 5 superfluous instructions for this
one argument syscall)
This commit changes the RISC-V syscall code such that only the required
syscall argument registers are set.
GCC detects that argc is known at compile time and thus evaluates all the
if-statements where argc is used at compile time (tested with -O2 and -Os).
77 lines
2.0 KiB
C
77 lines
2.0 KiB
C
/* Copyright (c) 2017 SiFive Inc. All rights reserved.
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This copyrighted material is made available to anyone wishing to use,
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modify, copy, or redistribute it subject to the terms and conditions
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of the FreeBSD License. This program is distributed in the hope that
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it will be useful, but WITHOUT ANY WARRANTY expressed or implied,
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including the implied warranties of MERCHANTABILITY or FITNESS FOR
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A PARTICULAR PURPOSE. A copy of this license is available at
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http://www.opensource.org/licenses.
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*/
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#ifndef _INTERNAL_SYSCALL_H
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#define _INTERNAL_SYSCALL_H
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#include <errno.h>
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static inline long
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__syscall_error(long a0)
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{
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errno = -a0;
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return -1;
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}
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static inline long
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__internal_syscall(long n, int argc, long _a0, long _a1, long _a2, long _a3, long _a4, long _a5)
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{
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#ifdef __riscv_32e
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register long syscall_id asm("t0") = n;
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#else
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register long syscall_id asm("a7") = n;
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#endif
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register long a0 asm("a0") = _a0;
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if (argc < 2) {
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asm volatile ("ecall" : "+r"(a0) : "r"(syscall_id));
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return a0;
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}
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register long a1 asm("a1") = _a1;
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if (argc == 2) {
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asm volatile ("ecall" : "+r"(a0) : "r"(a1), "r"(syscall_id));
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return a0;
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}
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register long a2 asm("a2") = _a2;
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if (argc == 3) {
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asm volatile ("ecall" : "+r"(a0) : "r"(a1), "r"(a2), "r"(syscall_id));
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return a0;
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}
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register long a3 asm("a3") = _a3;
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if (argc == 4) {
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asm volatile ("ecall" : "+r"(a0) : "r"(a1), "r"(a2), "r"(a3), "r"(syscall_id));
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return a0;
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}
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register long a4 asm("a4") = _a4;
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if (argc == 5) {
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asm volatile ("ecall" : "+r"(a0) : "r"(a1), "r"(a2), "r"(a3), "r"(a4), "r"(syscall_id));
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return a0;
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}
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register long a5 asm("a5") = _a5;
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asm volatile ("ecall" : "+r"(a0) : "r"(a1), "r"(a2), "r"(a3), "r"(a4), "r"(a5), "r"(syscall_id));
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return a0;
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}
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static inline long
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syscall_errno(long n, int argc, long _a0, long _a1, long _a2, long _a3, long _a4, long _a5)
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{
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long a0 = __internal_syscall (n, argc, _a0, _a1, _a2, _a3, _a4, _a5);
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if (a0 < 0)
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return __syscall_error (a0);
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else
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return a0;
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}
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#endif
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