[IA64] prevent accidental modification of args in jprobe handler

When jprobe is hit, the function parameters of the original function
should be saved before jprobe handler is executed, and restored it after
jprobe handler is executed, because jprobe handler might change the
register values due to tail call optimization by the gcc.

Signed-off-by: Zhang Yanmin <yanmin.zhang@intel.com>
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

diff --git a/arch/ia64/kernel/jprobes.S b/arch/ia64/kernel/jprobes.S
index 2323377e36950ee236a662bcddada08c2f423d45..5cd6226f44f291c2a9a4fd2fa42374148fc65ab9 100644 (file)
--- a/arch/ia64/kernel/jprobes.S
+++ b/arch/ia64/kernel/jprobes.S
@@ -60,3 +60,30 @@ END(jprobe_break)
 GLOBAL_ENTRY(jprobe_inst_return)
        br.call.sptk.many b0=jprobe_break
 END(jprobe_inst_return)
+
+GLOBAL_ENTRY(invalidate_stacked_regs)
+       movl r16=invalidate_restore_cfm
+       ;;
+       mov b6=r16
+       ;;
+       br.ret.sptk.many b6
+       ;;
+invalidate_restore_cfm:
+       mov r16=ar.rsc
+       ;;
+       mov ar.rsc=r0
+       ;;
+       loadrs
+       ;;
+       mov ar.rsc=r16
+       ;;
+       br.cond.sptk.many rp
+END(invalidate_stacked_regs)
+
+GLOBAL_ENTRY(flush_register_stack)
+       // flush dirty regs to backing store (must be first in insn group)
+       flushrs
+       ;;
+       br.ret.sptk.many rp
+END(flush_register_stack)
+

diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 346fedf9ea479a361ea7cdca2173b442b2302adb..50ae8c7d453d5075641a191dcfdf5bf0d4087ece 100644 (file)
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -766,11 +766,56 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
        return ret;
 }
 
+struct param_bsp_cfm {
+       unsigned long ip;
+       unsigned long *bsp;
+       unsigned long cfm;
+};
+
+static void ia64_get_bsp_cfm(struct unw_frame_info *info, void *arg)
+{
+       unsigned long ip;
+       struct param_bsp_cfm *lp = arg;
+
+       do {
+               unw_get_ip(info, &ip);
+               if (ip == 0)
+                       break;
+               if (ip == lp->ip) {
+                       unw_get_bsp(info, (unsigned long*)&lp->bsp);
+                       unw_get_cfm(info, (unsigned long*)&lp->cfm);
+                       return;
+               }
+       } while (unw_unwind(info) >= 0);
+       lp->bsp = 0;
+       lp->cfm = 0;
+       return;
+}
+
 int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 {
        struct jprobe *jp = container_of(p, struct jprobe, kp);
        unsigned long addr = ((struct fnptr *)(jp->entry))->ip;
        struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+       struct param_bsp_cfm pa;
+       int bytes;
+
+       /*
+        * Callee owns the argument space and could overwrite it, eg
+        * tail call optimization. So to be absolutely safe
+        * we save the argument space before transfering the control
+        * to instrumented jprobe function which runs in
+        * the process context
+        */
+       pa.ip = regs->cr_iip;
+       unw_init_running(ia64_get_bsp_cfm, &pa);
+       bytes = (char *)ia64_rse_skip_regs(pa.bsp, pa.cfm & 0x3f)
+                               - (char *)pa.bsp;
+       memcpy( kcb->jprobes_saved_stacked_regs,
+               pa.bsp,
+               bytes );
+       kcb->bsp = pa.bsp;
+       kcb->cfm = pa.cfm;
 
        /* save architectural state */
        kcb->jprobe_saved_regs = *regs;
@@ -792,8 +837,20 @@ int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 {
        struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+       int bytes;
 
+       /* restoring architectural state */
        *regs = kcb->jprobe_saved_regs;
+
+       /* restoring the original argument space */
+       flush_register_stack();
+       bytes = (char *)ia64_rse_skip_regs(kcb->bsp, kcb->cfm & 0x3f)
+                               - (char *)kcb->bsp;
+       memcpy( kcb->bsp,
+               kcb->jprobes_saved_stacked_regs,
+               bytes );
+       invalidate_stacked_regs();
+
        preempt_enable_no_resched();
        return 1;
 }

diff --git a/include/asm-ia64/kprobes.h b/include/asm-ia64/kprobes.h
index a74b68104559a556e335e80b7262c46594086a89..8c0fc227f0fb6934c4f3f7573456d5d21150c6e0 100644 (file)
--- a/include/asm-ia64/kprobes.h
+++ b/include/asm-ia64/kprobes.h
@@ -68,10 +68,14 @@ struct prev_kprobe {
        unsigned long status;
 };
 
+#define        MAX_PARAM_RSE_SIZE      (0x60+0x60/0x3f)
 /* per-cpu kprobe control block */
 struct kprobe_ctlblk {
        unsigned long kprobe_status;
        struct pt_regs jprobe_saved_regs;
+       unsigned long jprobes_saved_stacked_regs[MAX_PARAM_RSE_SIZE];
+       unsigned long *bsp;
+       unsigned long cfm;
        struct prev_kprobe prev_kprobe;
 };
 
@@ -118,5 +122,7 @@ extern int kprobe_exceptions_notify(struct notifier_block *self,
 static inline void jprobe_return(void)
 {
 }
+extern void invalidate_stacked_regs(void);
+extern void flush_register_stack(void);
 
 #endif                         /* _ASM_KPROBES_H */