minix/kernel/system/do_sigreturn.c
Tomas Hruby cbc9586c13 Lazy FPU
- FPU context is stored only if conflict between 2 FPU users or while
  exporting context of a process to userspace while it is the active
  user of FPU

- FPU has its owner (fpu_owner) which points to the process whose
  state is currently loaded in FPU

- the FPU exception is only turned on when scheduling a process which
  is not the owner of FPU

- FPU state is restored for the process that generated the FPU
  exception. This process runs immediately without letting scheduler
  to pick a new process to resolve the FPU conflict asap, to minimize
  the FPU thrashing and FPU exception hadler execution

- faster all non-FPU-exception kernel entries as FPU state is not
  checked nor saved

- removed MF_USED_FPU flag, only MF_FPU_INITIALIZED remains to signal
  that a process has used FPU in the past
2010-06-07 07:43:17 +00:00

71 lines
2 KiB
C

/* The kernel call that is implemented in this file:
* m_type: SYS_SIGRETURN
*
* The parameters for this kernel call are:
* m2_i1: SIG_ENDPT # process returning from handler
* m2_p1: SIG_CTXT_PTR # pointer to sigcontext structure
*
*/
#include "kernel/system.h"
#include <string.h>
#include <machine/cpu.h>
#include <sys/sigcontext.h>
#if USE_SIGRETURN
/*===========================================================================*
* do_sigreturn *
*===========================================================================*/
PUBLIC int do_sigreturn(struct proc * caller, message * m_ptr)
{
/* POSIX style signals require sys_sigreturn to put things in order before
* the signalled process can resume execution
*/
struct sigcontext sc;
register struct proc *rp;
int proc_nr, r;
if (! isokendpt(m_ptr->SIG_ENDPT, &proc_nr)) return(EINVAL);
if (iskerneln(proc_nr)) return(EPERM);
rp = proc_addr(proc_nr);
/* Copy in the sigcontext structure. */
if((r=data_copy(m_ptr->SIG_ENDPT, (vir_bytes) m_ptr->SIG_CTXT_PTR,
KERNEL, (vir_bytes) &sc, sizeof(struct sigcontext))) != OK)
return r;
/* Restore user bits of psw from sc, maintain system bits from proc. */
sc.sc_psw = (sc.sc_psw & X86_FLAGS_USER) |
(rp->p_reg.psw & ~X86_FLAGS_USER);
#if (_MINIX_CHIP == _CHIP_INTEL)
/* Don't panic kernel if user gave bad selectors. */
sc.sc_cs = rp->p_reg.cs;
sc.sc_ds = rp->p_reg.ds;
sc.sc_es = rp->p_reg.es;
sc.sc_ss = rp->p_reg.ss;
#if _WORD_SIZE == 4
sc.sc_fs = rp->p_reg.fs;
sc.sc_gs = rp->p_reg.gs;
#endif
#endif
/* Restore the registers. */
memcpy(&rp->p_reg, &sc.sc_regs, sizeof(sigregs));
#if (_MINIX_CHIP == _CHIP_INTEL)
if(sc.sc_flags & MF_FPU_INITIALIZED)
{
memcpy(rp->p_fpu_state.fpu_save_area_p, &sc.sc_fpu_state,
FPU_XFP_SIZE);
rp->p_misc_flags |= MF_FPU_INITIALIZED; /* Restore math usage flag. */
/* force reloading FPU */
if (fpu_owner == rp)
release_fpu();
}
#endif
return(OK);
}
#endif /* USE_SIGRETURN */