newlib-cygwin/libgloss/riscv/sys_fstat.c

#include <machine/syscall.h>
#include "kernel_stat.h"
#include "internal_syscall.h"

/* Status of an open file. The sys/stat.h header file required is
   distributed in the include subdirectory for this C library.  */

int
_fstat(int file, struct stat *st)
{
  struct kernel_stat kst;
  int rv = syscall_errno (SYS_fstat, 2, file, &kst, 0, 0, 0, 0);
  _conv_stat (st, &kst);
  return rv;
}
RISC-V: Moved syscalls to separate files to fix aliasing problems. 2017-12-27 04:27:52 +08:00			`#include <machine/syscall.h>`
			`#include "kernel_stat.h"`
			`#include "internal_syscall.h"`

			`/* Status of an open file. The sys/stat.h header file required is`
			`distributed in the include subdirectory for this C library. */`

			`int`
			`_fstat(int file, struct stat *st)`
			`{`
			`struct kernel_stat kst;`
Only pass the minimum number of syscall arguments 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). 2020-02-11 04:19:58 +08:00			`int rv = syscall_errno (SYS_fstat, 2, file, &kst, 0, 0, 0, 0);`
RISC-V: Moved syscalls to separate files to fix aliasing problems. 2017-12-27 04:27:52 +08:00			`_conv_stat (st, &kst);`
			`return rv;`
			`}`