mirror of
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).
57 lines
1.3 KiB
C
57 lines
1.3 KiB
C
#ifdef USING_SIM_SPECS
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// Gdb simulator requires that sbrk be implemented without a syscall.
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extern char _end[]; /* _end is set in the linker command file */
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char *heap_ptr;
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/*
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* sbrk -- changes heap size size. Get nbytes more
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* RAM. We just increment a pointer in what's
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* left of memory on the board.
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*/
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char *
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_sbrk (nbytes)
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int nbytes;
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{
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char *base;
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if (!heap_ptr)
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heap_ptr = (char *)&_end;
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base = heap_ptr;
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heap_ptr += nbytes;
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return base;
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}
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#else
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// QEMU uses a syscall.
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#include <machine/syscall.h>
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#include <sys/types.h>
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#include "internal_syscall.h"
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/* Increase program data space. As malloc and related functions depend
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on this, it is useful to have a working implementation. The following
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is suggested by the newlib docs and suffices for a standalone
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system. */
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void *
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_sbrk(ptrdiff_t incr)
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{
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static unsigned long heap_end;
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if (heap_end == 0)
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{
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long brk = __internal_syscall (SYS_brk, 1, 0, 0, 0, 0, 0, 0);
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if (brk == -1)
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return (void *)__syscall_error (-ENOMEM);
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heap_end = brk;
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}
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if (__internal_syscall (SYS_brk, 1, heap_end + incr, 0, 0, 0, 0, 0) != heap_end + incr)
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return (void *)__syscall_error (-ENOMEM);
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heap_end += incr;
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return (void *)(heap_end - incr);
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}
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#endif
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