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).
16 lines
390 B
C
16 lines
390 B
C
#include <machine/syscall.h>
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#include "kernel_stat.h"
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#include "internal_syscall.h"
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/* Status of an open file. The sys/stat.h header file required is
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distributed in the include subdirectory for this C library. */
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int
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_fstat(int file, struct stat *st)
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{
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struct kernel_stat kst;
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int rv = syscall_errno (SYS_fstat, 2, file, &kst, 0, 0, 0, 0);
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_conv_stat (st, &kst);
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return rv;
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}
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