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Message-Id: <1276612969-13508-3-git-send-email-hschauhan@nulltrace.org>
Date: Tue, 15 Jun 2010 20:12:49 +0530
From: Himanshu Chauhan <hschauhan@...ltrace.org>
To: linux-kernel@...r.kernel.org
Cc: ralf@...ux-mips.org, linux-mips@...ux-mips.org,
ddaney@...iumnetworks.com
Subject: [PATCH 2/2] MIPS: Kretprobe support
This patch adds support for kretprobes on MIPS architecture.
Signed-off-by: Himanshu Chauhan <hschauhan@...ltrace.org>
---
arch/mips/Kconfig | 1 +
arch/mips/kernel/kprobes.c | 117 +++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 117 insertions(+), 1 deletions(-)
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index ba7cc87..8dd82cf 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -2248,6 +2248,7 @@ menu "Instrumentation Support"
config KPROBES
bool "MIPS Kprobes Support (Experimental)"
depends on EXPERIMENTAL && MODULES
+ select HAVE_KRETPROBES
help
Kprobes allow you to trap at almost any kernel address
and execute a callback function. Kprobes is useful for
diff --git a/arch/mips/kernel/kprobes.c b/arch/mips/kernel/kprobes.c
index 6b6689f..07e8a04 100644
--- a/arch/mips/kernel/kprobes.c
+++ b/arch/mips/kernel/kprobes.c
@@ -4,7 +4,9 @@
*
* Copyright 2006 Sony Corp.
*
- * Himanshu Chauhan <hschauhan@...ltrace.org> for >2.6.35 kernels.
+ * (C) 2010 Himanshu Chauhan <hschauhan@...ltrace.org>
+ * o Kprobes replay on kernels >2.6.35
+ * o Added support for kretprobes.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@@ -24,6 +26,7 @@
#include <linux/kdebug.h>
#include <linux/kprobes.h>
#include <linux/preempt.h>
+#include <linux/slab.h>
#include <asm/cacheflush.h>
#include <asm/inst.h>
#include <asm/ptrace.h>
@@ -358,6 +361,113 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
return ret;
}
+/*
+ * When a retprobed function returns, trampoline_handler() is called,
+ * calling the kretprobe's handler. We need to generate a pt_regs
+ * frame before calling trampoline_handler. Saving RA here makes no
+ * sense because kretprobe_trampoline will have no RA, rather
+ * RA will be returned by trampoline_handler. We would only be
+ * interested in saving v0 and v1 i.e. the return value of the
+ * probed function.
+ */
+void notrace __kprobes kretprobe_trampoline(void)
+{
+ __asm__ __volatile__ (
+ ".set noreorder\n\t"
+#ifdef CONFIG_32BIT
+ "addiu $29, -152\n\t"
+ "sw $2, 32($29)\n\t"
+ "sw $3, 36($29)\n\t"
+#else
+ "addiu $29, -128\n\t"
+ "sw $2, 8($29)\n\t"
+ "sw $3, 12($29)\n\t"
+#endif
+ "jal trampoline_handler\n\t"
+ "move $4, $29\n\t"
+ "move $31, $2\n\t"
+#ifdef CONFIG_32BIT
+ "lw $2, 32($29)\n\t"
+ "lw $3, 36($29)\n\t"
+ "addiu $29, 152\n\t"
+#else
+ "lw $2, 8($29)\n\t"
+ "lw $3, 12($29)\n\t"
+ "addiu $29, 128\n\t"
+#endif
+ : : : "memory");
+}
+
+/* Called from kretprobe_trampoline */
+static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
+{
+ struct kretprobe_instance *ri = NULL;
+ struct hlist_head *head, empty_rp;
+ struct hlist_node *node, *tmp;
+ unsigned long flags, orig_ret_address = 0;
+ unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
+
+ INIT_HLIST_HEAD(&empty_rp);
+ kretprobe_hash_lock(current, &head, &flags);
+
+ /*
+ * It is possible to have multiple instances associated with a given
+ * task either because multiple functions in the call path have
+ * a return probe installed on them, and/or more than one return
+ * probe was registered for a target function.
+ *
+ * We can handle this because:
+ * - instances are always inserted at the head of the list
+ * - when multiple return probes are registered for the same
+ * function, the first instance's ret_addr will point to the
+ * real return address, and all the rest will point to
+ * kretprobe_trampoline
+ */
+ hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
+ if (ri->task != current)
+ /* another task is sharing our hash bucket */
+ continue;
+
+ if (ri->rp && ri->rp->handler) {
+ __get_cpu_var(current_kprobe) = &ri->rp->kp;
+ get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
+ ri->rp->handler(ri, regs);
+ __get_cpu_var(current_kprobe) = NULL;
+ }
+
+ orig_ret_address = (unsigned long)ri->ret_addr;
+ recycle_rp_inst(ri, &empty_rp);
+
+ if (orig_ret_address != trampoline_address)
+ /*
+ * This is the real return address. Any other
+ * instances associated with this task are for
+ * other calls deeper on the call stack
+ */
+ break;
+ }
+
+ kretprobe_assert(ri, orig_ret_address, trampoline_address);
+ kretprobe_hash_unlock(current, &flags);
+
+ hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
+ hlist_del(&ri->hlist);
+ kfree(ri);
+ }
+
+ return (void *)orig_ret_address;
+}
+
+void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
+ struct pt_regs *regs)
+{
+ /* save the ra */
+ ri->ret_addr = (kprobe_opcode_t *)regs->regs[31];
+
+ /* Replace the return addr with trampoline addr. */
+ regs->regs[31] = (unsigned long)&kretprobe_trampoline;
+}
+
int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
return 0;
@@ -376,3 +486,8 @@ int __init arch_init_kprobes(void)
{
return 0;
}
+
+int __kprobes arch_trampoline_kprobe(struct kprobe *p)
+{
+ return 0;
+}
--
1.7.0.4
--
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