patch-2.4.21 linux-2.4.21/arch/ppc/mm/fault.c
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- Lines: 91
- Date:
2003-06-13 07:51:31.000000000 -0700
- Orig file:
linux-2.4.20/arch/ppc/mm/fault.c
- Orig date:
2002-11-28 15:53:11.000000000 -0800
diff -urN linux-2.4.20/arch/ppc/mm/fault.c linux-2.4.21/arch/ppc/mm/fault.c
@@ -1,7 +1,4 @@
/*
- * BK Id: SCCS/s.fault.c 1.15 09/24/01 16:35:10 paulus
- */
-/*
* arch/ppc/mm/fault.c
*
* PowerPC version
@@ -56,6 +53,41 @@
void do_page_fault(struct pt_regs *, unsigned long, unsigned long);
/*
+ * Check whether the instruction at regs->nip is a store using
+ * an update addressing form which will update r1.
+ */
+static int store_updates_sp(struct pt_regs *regs)
+{
+ unsigned int inst;
+
+ if (get_user(inst, (unsigned int *)regs->nip))
+ return 0;
+ /* check for 1 in the rA field */
+ if (((inst >> 16) & 0x1f) != 1)
+ return 0;
+ /* check major opcode */
+ switch (inst >> 26) {
+ case 37: /* stwu */
+ case 39: /* stbu */
+ case 45: /* sthu */
+ case 53: /* stfsu */
+ case 55: /* stfdu */
+ return 1;
+ case 31:
+ /* check minor opcode */
+ switch ((inst >> 1) & 0x3ff) {
+ case 183: /* stwux */
+ case 247: /* stbux */
+ case 439: /* sthux */
+ case 695: /* stfsux */
+ case 759: /* stfdux */
+ return 1;
+ }
+ }
+ return 0;
+}
+
+/*
* For 600- and 800-family processors, the error_code parameter is DSISR
* for a data fault, SRR1 for an instruction fault. For 400-family processors
* the error_code parameter is ESR for a data fault, 0 for an instruction
@@ -111,6 +143,40 @@
goto good_area;
if (!(vma->vm_flags & VM_GROWSDOWN))
goto bad_area;
+ if (!is_write)
+ goto bad_area;
+
+ /*
+ * N.B. The rs6000/xcoff ABI allows programs to access up to
+ * a few hundred bytes below the stack pointer.
+ * The kernel signal delivery code writes up to about 1.5kB
+ * below the stack pointer (r1) before decrementing it.
+ * The exec code can write slightly over 640kB to the stack
+ * before setting the user r1. Thus we allow the stack to
+ * expand to 1MB without further checks.
+ */
+ if (address + 0x100000 < vma->vm_end) {
+ /* get user regs even if this fault is in kernel mode */
+ struct pt_regs *uregs = current->thread.regs;
+ if (uregs == NULL)
+ goto bad_area;
+
+ /*
+ * A user-mode access to an address a long way below
+ * the stack pointer is only valid if the instruction
+ * is one which would update the stack pointer to the
+ * address accessed if the instruction completed,
+ * i.e. either stwu rs,n(r1) or stwux rs,r1,rb
+ * (or the byte, halfword, float or double forms).
+ *
+ * If we don't check this then any write to the area
+ * between the last mapped region and the stack will
+ * expand the stack rather than segfaulting.
+ */
+ if (address + 2048 < uregs->gpr[1]
+ && (!user_mode(regs) || !store_updates_sp(regs)))
+ goto bad_area;
+ }
if (expand_stack(vma, address))
goto bad_area;
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