Commit 9b046d02 authored by Helge Deller's avatar Helge Deller
Browse files

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: default avatarHelge Deller <deller@gmx.de>
parent 46162ac2

arch/parisc/include/asm/kprobes.h

+3 −2
Original line number Diff line number Diff line
@@ -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

arch/parisc/kernel/kprobes.c

+17 −11
Original line number Diff line number Diff line
@@ -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)

{

arch/parisc/kernel/traps.c

+4 −6
Original line number Diff line number Diff line
@@ -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);