parisc: Avoid using hardware single-step in kprobes

This patch changes the kprobe and kretprobe feature to use another
break instruction instead of relying on the hardware single-step
feature.
That way those kprobes now work in qemu as well, because in qemu we
don't emulate yet single-stepping.

Signed-off-by: Helge Deller <deller@gmx.de>

diff --git a/arch/parisc/include/asm/kprobes.h b/arch/parisc/include/asm/kprobes.h
index 904034d..0a175ac 100644 (file)
--- a/arch/parisc/include/asm/kprobes.h
+++ b/arch/parisc/include/asm/kprobes.h
@@ -18,8 +18,9 @@
 #include <linux/notifier.h>
 
 #define PARISC_KPROBES_BREAK_INSN      0x3ff801f
+#define PARISC_KPROBES_BREAK_INSN2     0x3ff801e
 #define  __ARCH_WANT_KPROBES_INSN_SLOT
-#define MAX_INSN_SIZE 1
+#define MAX_INSN_SIZE 2
 
 typedef u32 kprobe_opcode_t;
 struct kprobe;
@@ -29,7 +30,7 @@ void arch_remove_kprobe(struct kprobe *p);
 #define flush_insn_slot(p) \
        flush_icache_range((unsigned long)&(p)->ainsn.insn[0], \
                           (unsigned long)&(p)->ainsn.insn[0] + \
-                          sizeof(kprobe_opcode_t))
+                          MAX_INSN_SIZE*sizeof(kprobe_opcode_t))
 
 #define kretprobe_blacklist_size    0
 

diff --git a/arch/parisc/kernel/kprobes.c b/arch/parisc/kernel/kprobes.c
index e2bdb5a..3343d2f 100644 (file)
--- a/arch/parisc/kernel/kprobes.c
+++ b/arch/parisc/kernel/kprobes.c
@@ -5,6 +5,7 @@
  * PA-RISC kprobes implementation
  *
  * Copyright (c) 2019 Sven Schnelle <svens@stackframe.org>
+ * Copyright (c) 2022 Helge Deller <deller@gmx.de>
  */
 
 #include <linux/types.h>
@@ -25,9 +26,14 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
        if (!p->ainsn.insn)
                return -ENOMEM;
 
-       memcpy(p->ainsn.insn, p->addr,
-               MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+       /*
+        * Set up new instructions. Second break instruction will
+        * trigger call of parisc_kprobe_ss_handler().
+        */
        p->opcode = *p->addr;
+       p->ainsn.insn[0] = p->opcode;
+       p->ainsn.insn[1] = PARISC_KPROBES_BREAK_INSN2;
+
        flush_insn_slot(p);
        return 0;
 }
@@ -73,9 +79,7 @@ static void __kprobes setup_singlestep(struct kprobe *p,
 {
        kcb->iaoq[0] = regs->iaoq[0];
        kcb->iaoq[1] = regs->iaoq[1];
-       regs->iaoq[0] = (unsigned long)p->ainsn.insn;
-       mtctl(0, 0);
-       regs->gr[0] |= PSW_R;
+       instruction_pointer_set(regs, (unsigned long)p->ainsn.insn);
 }
 
 int __kprobes parisc_kprobe_break_handler(struct pt_regs *regs)
@@ -165,9 +169,8 @@ int __kprobes parisc_kprobe_ss_handler(struct pt_regs *regs)
                regs->iaoq[0] = kcb->iaoq[1];
                break;
        default:
-               regs->iaoq[1] = kcb->iaoq[0];
-               regs->iaoq[1] += (regs->iaoq[1] - regs->iaoq[0]) + 4;
                regs->iaoq[0] = kcb->iaoq[1];
+               regs->iaoq[1] = regs->iaoq[0] + 4;
                break;
        }
        kcb->kprobe_status = KPROBE_HIT_SSDONE;
@@ -191,14 +194,17 @@ static struct kprobe trampoline_p = {
 static int __kprobes trampoline_probe_handler(struct kprobe *p,
                                              struct pt_regs *regs)
 {
-       unsigned long orig_ret_address;
-
-       orig_ret_address = __kretprobe_trampoline_handler(regs, NULL);
-       instruction_pointer_set(regs, orig_ret_address);
+       __kretprobe_trampoline_handler(regs, NULL);
 
        return 1;
 }
 
+void arch_kretprobe_fixup_return(struct pt_regs *regs,
+                                kprobe_opcode_t *correct_ret_addr)
+{
+       regs->gr[2] = (unsigned long)correct_ret_addr;
+}
+
 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
                                      struct pt_regs *regs)
 {

diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c
index 39576a9..a6e61cf 100644 (file)
--- a/arch/parisc/kernel/traps.c
+++ b/arch/parisc/kernel/traps.c
@@ -302,7 +302,10 @@ static void handle_break(struct pt_regs *regs)
                parisc_kprobe_break_handler(regs);
                return;
        }
-
+       if (unlikely(iir == PARISC_KPROBES_BREAK_INSN2)) {
+               parisc_kprobe_ss_handler(regs);
+               return;
+       }
 #endif
 
 #ifdef CONFIG_KGDB
@@ -539,11 +542,6 @@ void notrace handle_interruption(int code, struct pt_regs *regs)
                /* Recovery counter trap */
                regs->gr[0] &= ~PSW_R;
 
-#ifdef CONFIG_KPROBES
-               if (parisc_kprobe_ss_handler(regs))
-                       return;
-#endif
-
 #ifdef CONFIG_KGDB
                if (kgdb_single_step) {
                        kgdb_handle_exception(0, SIGTRAP, 0, regs);