[XTENSA] Allow debugger to modify the WINDOWBASE register.

For the 'return' command, GDB needs to adjust WINDOWBASE.
In case WB is different from 0, we need to rotate the
window register file and update WINDOWSTART and WMASK.
This patch also removes some ret|= statements for
__get_user/__put_user as the address range was alrady
checked a couple of lines earlier.
Signed-off-by: Chris Zankel <chris@zankel.net>

arch/xtensa/kernel/ptrace.c

@@ -43,32 +43,29 @@ int ptrace_getregs(struct task_struct *child, void __user *uregs)
 {
 	struct pt_regs *regs = task_pt_regs(child);
 	xtensa_gregset_t __user *gregset = uregs;
-	unsigned long wb = regs->windowbase;
-	unsigned long ws = regs->windowstart;
 	unsigned long wm = regs->wmask;
-	int ret = 0;
-	int live, last;
+	unsigned long wb = regs->windowbase;
+	int live, i;
 
 	if (!access_ok(VERIFY_WRITE, uregs, sizeof(xtensa_gregset_t)))
 		return -EIO;
 
-	/* Norm windowstart to a windowbase of 0. */
-
-	ws = ((ws>>wb) | (ws<<(WSBITS-wb))) & ((1<<WSBITS)-1);
-
-	ret |= __put_user(regs->pc, &gregset->pc);
-	ret |= __put_user(regs->ps & ~(1 << PS_EXCM_BIT), &gregset->ps);
-	ret |= __put_user(regs->lbeg, &gregset->lbeg);
-	ret |= __put_user(regs->lend, &gregset->lend);
-	ret |= __put_user(regs->lcount, &gregset->lcount);
-	ret |= __put_user(ws, &gregset->windowstart);
+	__put_user(regs->pc, &gregset->pc);
+	__put_user(regs->ps & ~(1 << PS_EXCM_BIT), &gregset->ps);
+	__put_user(regs->lbeg, &gregset->lbeg);
+	__put_user(regs->lend, &gregset->lend);
+	__put_user(regs->lcount, &gregset->lcount);
+	__put_user(regs->windowstart, &gregset->windowstart);
+	__put_user(regs->windowbase, &gregset->windowbase);
 
 	live = (wm & 2) ? 4 : (wm & 4) ? 8 : (wm & 8) ? 12 : 16;
-	last = XCHAL_NUM_AREGS - (wm >> 4) * 4;
-	ret |= __copy_to_user(gregset->a, regs->areg, live * 4);
-	ret |= __copy_to_user(gregset->a + last, regs->areg + last, (wm>>4)*16);
 
-	return ret ? -EFAULT : 0;
+	for (i = 0; i < live; i++)
+		__put_user(regs->areg[i],gregset->a+((wb*4+i)%XCHAL_NUM_AREGS));
+	for (i = XCHAL_NUM_AREGS - (wm >> 4) * 4; i < XCHAL_NUM_AREGS; i++)
+		__put_user(regs->areg[i],gregset->a+((wb*4+i)%XCHAL_NUM_AREGS));
+
+	return 0;
 }
 
 int ptrace_setregs(struct task_struct *child, void __user *uregs)
@@ -76,28 +73,35 @@ int ptrace_setregs(struct task_struct *child, void __user *uregs)
 	struct pt_regs *regs = task_pt_regs(child);
 	xtensa_gregset_t *gregset = uregs;
 	const unsigned long ps_mask = PS_CALLINC_MASK | PS_OWB_MASK;
-	unsigned long wm = regs->wmask;
 	unsigned long ps;
-	int ret = 0;
-	int live, last;
+	unsigned long wb;
 
 	if (!access_ok(VERIFY_WRITE, uregs, sizeof(xtensa_gregset_t)))
 		return -EIO;
 
-	ret |= __get_user(regs->pc, &gregset->pc);
-	ret |= __get_user(ps, &gregset->ps);
-	ret |= __get_user(regs->lbeg, &gregset->lbeg);
-	ret |= __get_user(regs->lend, &gregset->lend);
-	ret |= __get_user(regs->lcount, &gregset->lcount);
+	__get_user(regs->pc, &gregset->pc);
+	__get_user(ps, &gregset->ps);
+	__get_user(regs->lbeg, &gregset->lbeg);
+	__get_user(regs->lend, &gregset->lend);
+	__get_user(regs->lcount, &gregset->lcount);
+	__get_user(regs->windowstart, &gregset->windowstart);
+	__get_user(wb, &gregset->windowbase);
 
 	regs->ps = (regs->ps & ~ps_mask) | (ps & ps_mask) | (1 << PS_EXCM_BIT);
 
-	live = (wm & 2) ? 4 : (wm & 4) ? 8 : (wm & 8) ? 12 : 16;
-	last = XCHAL_NUM_AREGS - (wm >> 4) * 4;
-	ret |= __copy_from_user(regs->areg, gregset->a, live * 4);
-	ret |= __copy_from_user(regs->areg+last, gregset->a+last, (wm>>4)*16);
+	if (wb >= XCHAL_NUM_AREGS / 4)
+		return -EFAULT;
 
-	return ret ? -EFAULT : 0;
+	regs->windowbase = wb;
+
+	if (wb != 0 &&  __copy_from_user(regs->areg + XCHAL_NUM_AREGS - wb * 4,
+					 gregset->a, wb * 16))
+		return -EFAULT;
+
+	if (__copy_from_user(regs->areg, gregset->a + wb*4, (WSBITS-wb) * 16))
+		return -EFAULT;
+
+	return 0;
 }
 
 

include/asm-xtensa/elf.h

@@ -82,7 +82,8 @@ typedef struct {
 	elf_greg_t lcount;
 	elf_greg_t sar;
 	elf_greg_t windowstart;
-	elf_greg_t reserved[9+48];
+	elf_greg_t windowbase;
+	elf_greg_t reserved[8+48];
 	elf_greg_t a[64];
 } xtensa_gregset_t;