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[XTENSA] Add support for configurable registers and coprocessors

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The Xtensa architecture allows to define custom instructions and
registers. Registers that are bound to a coprocessor are only
accessible if the corresponding enable bit is set, which allows
to implement a 'lazy' context switch mechanism. Other registers
needs to be saved and restore at the time of the context switch
or during interrupt handling.

This patch adds support for these additional states:

- save and restore registers that are used by the compiler upon
  interrupt entry and exit.
- context switch additional registers unbound to any coprocessor
- 'lazy' context switch of registers bound to a coprocessor
- ptrace interface to provide access to additional registers
- update configuration files in include/asm-xtensa/variant-fsf

Signed-off-by: Chris Zankel <chris@zankel.net>
This commit is contained in:
Chris Zankel
2008-02-12 13:17:07 -08:00
parent 71d28e6c28
commit c658eac628
17 changed files with 1076 additions and 885 deletions
Download Patch File Download Diff File Expand all files Collapse all files

261
arch/xtensa/kernel/process.c
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@@ -52,6 +52,55 @@ void (*pm_power_off)(void) = NULL;
EXPORT_SYMBOL(pm_power_off);
#if XTENSA_HAVE_COPROCESSORS
void coprocessor_release_all(struct thread_info *ti)
{
unsigned long cpenable;
int i;
/* Make sure we don't switch tasks during this operation. */
preempt_disable();
/* Walk through all cp owners and release it for the requested one. */
cpenable = ti->cpenable;
for (i = 0; i < XCHAL_CP_MAX; i++) {
if (coprocessor_owner[i] == ti) {
coprocessor_owner[i] = 0;
cpenable &= ~(1 << i);
}
}
ti->cpenable = cpenable;
coprocessor_clear_cpenable();
preempt_enable();
}
void coprocessor_flush_all(struct thread_info *ti)
{
unsigned long cpenable;
int i;
preempt_disable();
cpenable = ti->cpenable;
for (i = 0; i < XCHAL_CP_MAX; i++) {
if ((cpenable & 1) != 0 && coprocessor_owner[i] == ti)
coprocessor_flush(ti, i);
cpenable >>= 1;
}
preempt_enable();
}
#endif
/*
* Powermanagement idle function, if any is provided by the platform.
*/
@@ -71,15 +120,36 @@ void cpu_idle(void)
}
/*
* Free current thread data structures etc..
* This is called when the thread calls exit().
*/
void exit_thread(void)
{
#if XTENSA_HAVE_COPROCESSORS
coprocessor_release_all(current_thread_info());
#endif
}
/*
* Flush thread state. This is called when a thread does an execve()
* Note that we flush coprocessor registers for the case execve fails.
*/
void flush_thread(void)
{
#if XTENSA_HAVE_COPROCESSORS
struct thread_info *ti = current_thread_info();
coprocessor_flush_all(ti);
coprocessor_release_all(ti);
#endif
}
/*
* This is called before the thread is copied.
*/
void prepare_to_copy(struct task_struct *tsk)
{
#if XTENSA_HAVE_COPROCESSORS
coprocessor_flush_all(task_thread_info(tsk));
#endif
}
/*
@@ -107,6 +177,7 @@ int copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
struct task_struct * p, struct pt_regs * regs)
{
struct pt_regs *childregs;
struct thread_info *ti;
unsigned long tos;
int user_mode = user_mode(regs);
@@ -128,13 +199,14 @@ int copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
p->set_child_tid = p->clear_child_tid = NULL;
p->thread.ra = MAKE_RA_FOR_CALL((unsigned long)ret_from_fork, 0x1);
p->thread.sp = (unsigned long)childregs;
if (user_mode(regs)) {
int len = childregs->wmask & ~0xf;
childregs->areg[1] = usp;
memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4],
&regs->areg[XCHAL_NUM_AREGS - len/4], len);
// FIXME: we need to set THREADPTR in thread_info...
if (clone_flags & CLONE_SETTLS)
childregs->areg[2] = childregs->areg[6];
@@ -142,6 +214,12 @@ int copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
/* In kernel space, we start a new thread with a new stack. */
childregs->wmask = 1;
}
#if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
ti = task_thread_info(p);
ti->cpenable = 0;
#endif
return 0;
}
@@ -179,10 +257,6 @@ unsigned long get_wchan(struct task_struct *p)
}
/*
* do_copy_regs() gathers information from 'struct pt_regs' and
* 'current->thread.areg[]' to fill in the xtensa_gregset_t
* structure.
*
* xtensa_gregset_t and 'struct pt_regs' are vastly different formats
* of processor registers. Besides different ordering,
* xtensa_gregset_t contains non-live register information that
@@ -191,9 +265,20 @@ unsigned long get_wchan(struct task_struct *p)
*
*/
void do_copy_regs (xtensa_gregset_t *elfregs, struct pt_regs *regs,
struct task_struct *tsk)
void xtensa_elf_core_copy_regs (xtensa_gregset_t *elfregs, struct pt_regs *regs)
{
unsigned long wb, ws, wm;
int live, last;
wb = regs->windowbase;
ws = regs->windowstart;
wm = regs->wmask;
ws = ((ws >> wb) | (ws << (WSBITS - wb))) & ((1 << WSBITS) - 1);
/* Don't leak any random bits. */
memset(elfregs, 0, sizeof (elfregs));
/* Note: PS.EXCM is not set while user task is running; its
* being set in regs->ps is for exception handling convenience.
*/
@@ -204,159 +289,18 @@ void do_copy_regs (xtensa_gregset_t *elfregs, struct pt_regs *regs,
elfregs->lend = regs->lend;
elfregs->lcount = regs->lcount;
elfregs->sar = regs->sar;
elfregs->windowstart = ws;
memcpy (elfregs->a, regs->areg, sizeof(elfregs->a));
live = (wm & 2) ? 4 : (wm & 4) ? 8 : (wm & 8) ? 12 : 16;
last = XCHAL_NUM_AREGS - (wm >> 4) * 4;
memcpy(elfregs->a, regs->areg, live * 4);
memcpy(elfregs->a + last, regs->areg + last, (wm >> 4) * 16);
}
void xtensa_elf_core_copy_regs (xtensa_gregset_t *elfregs, struct pt_regs *regs)
int dump_fpu(void)
{
do_copy_regs ((xtensa_gregset_t *)elfregs, regs, current);
}
/* The inverse of do_copy_regs(). No error or sanity checking. */
void do_restore_regs (xtensa_gregset_t *elfregs, struct pt_regs *regs,
struct task_struct *tsk)
{
const unsigned long ps_mask = PS_CALLINC_MASK | PS_OWB_MASK;
unsigned long ps;
/* Note: PS.EXCM is not set while user task is running; it
* needs to be set in regs->ps is for exception handling convenience.
*/
ps = (regs->ps & ~ps_mask) | (elfregs->ps & ps_mask) | (1<<PS_EXCM_BIT);
regs->ps = ps;
regs->pc = elfregs->pc;
regs->lbeg = elfregs->lbeg;
regs->lend = elfregs->lend;
regs->lcount = elfregs->lcount;
regs->sar = elfregs->sar;
memcpy (regs->areg, elfregs->a, sizeof(regs->areg));
}
/*
* do_save_fpregs() gathers information from 'struct pt_regs' and
* 'current->thread' to fill in the elf_fpregset_t structure.
*
* Core files and ptrace use elf_fpregset_t.
*/
void do_save_fpregs (elf_fpregset_t *fpregs, struct pt_regs *regs,
struct task_struct *tsk)
{
#if XCHAL_HAVE_CP
extern unsigned char _xtensa_reginfo_tables[];
extern unsigned _xtensa_reginfo_table_size;
int i;
unsigned long flags;
/* Before dumping coprocessor state from memory,
* ensure any live coprocessor contents for this
* task are first saved to memory:
*/
local_irq_save(flags);
for (i = 0; i < XCHAL_CP_MAX; i++) {
if (tsk == coprocessor_info[i].owner) {
enable_coprocessor(i);
save_coprocessor_registers(
tsk->thread.cp_save+coprocessor_info[i].offset,i);
disable_coprocessor(i);
}
}
local_irq_restore(flags);
/* Now dump coprocessor & extra state: */
memcpy((unsigned char*)fpregs,
_xtensa_reginfo_tables, _xtensa_reginfo_table_size);
memcpy((unsigned char*)fpregs + _xtensa_reginfo_table_size,
tsk->thread.cp_save, XTENSA_CP_EXTRA_SIZE);
#endif
}
/*
* The inverse of do_save_fpregs().
* Copies coprocessor and extra state from fpregs into regs and tsk->thread.
* Returns 0 on success, non-zero if layout doesn't match.
*/
int do_restore_fpregs (elf_fpregset_t *fpregs, struct pt_regs *regs,
struct task_struct *tsk)
{
#if XCHAL_HAVE_CP
extern unsigned char _xtensa_reginfo_tables[];
extern unsigned _xtensa_reginfo_table_size;
int i;
unsigned long flags;
/* Make sure save area layouts match.
* FIXME: in the future we could allow restoring from
* a different layout of the same registers, by comparing
* fpregs' table with _xtensa_reginfo_tables and matching
* entries and copying registers one at a time.
* Not too sure yet whether that's very useful.
*/
if( memcmp((unsigned char*)fpregs,
_xtensa_reginfo_tables, _xtensa_reginfo_table_size) ) {
return -1;
}
/* Before restoring coprocessor state from memory,
* ensure any live coprocessor contents for this
* task are first invalidated.
*/
local_irq_save(flags);
for (i = 0; i < XCHAL_CP_MAX; i++) {
if (tsk == coprocessor_info[i].owner) {
enable_coprocessor(i);
save_coprocessor_registers(
tsk->thread.cp_save+coprocessor_info[i].offset,i);
coprocessor_info[i].owner = 0;
disable_coprocessor(i);
}
}
local_irq_restore(flags);
/* Now restore coprocessor & extra state: */
memcpy(tsk->thread.cp_save,
(unsigned char*)fpregs + _xtensa_reginfo_table_size,
XTENSA_CP_EXTRA_SIZE);
#endif
return 0;
}
/*
* Fill in the CP structure for a core dump for a particular task.
*/
int
dump_task_fpu(struct pt_regs *regs, struct task_struct *task, elf_fpregset_t *r)
{
return 0; /* no coprocessors active on this processor */
}
/*
* Fill in the CP structure for a core dump.
* This includes any FPU coprocessor.
* Here, we dump all coprocessors, and other ("extra") custom state.
*
* This function is called by elf_core_dump() in fs/binfmt_elf.c
* (in which case 'regs' comes from calls to do_coredump, see signals.c).
*/
int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
{
return dump_task_fpu(regs, current, r);
}
asmlinkage
long xtensa_clone(unsigned long clone_flags, unsigned long newsp,
@@ -370,8 +314,8 @@ long xtensa_clone(unsigned long clone_flags, unsigned long newsp,
}
/*
* * xtensa_execve() executes a new program.
* */
* xtensa_execve() executes a new program.
*/
asmlinkage
long xtensa_execve(char __user *name, char __user * __user *argv,
@@ -386,7 +330,6 @@ long xtensa_execve(char __user *name, char __user * __user *argv,
error = PTR_ERR(filename);
if (IS_ERR(filename))
goto out;
// FIXME: release coprocessor??
error = do_execve(filename, argv, envp, regs);
if (error == 0) {
task_lock(current);