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Message-Id: <1467995754-32508-10-git-send-email-dave.long@linaro.org>
Date: Fri, 8 Jul 2016 12:35:53 -0400
From: David Long <dave.long@...aro.org>
To: Catalin Marinas <catalin.marinas@....com>,
Huang Shijie <shijie.huang@....com>,
James Morse <james.morse@....com>,
Marc Zyngier <marc.zyngier@....com>,
Pratyush Anand <panand@...hat.com>,
Sandeepa Prabhu <sandeepa.s.prabhu@...il.com>,
Will Deacon <will.deacon@....com>,
William Cohen <wcohen@...hat.com>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Steve Capper <steve.capper@...aro.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Li Bin <huawei.libin@...wei.com>
Cc: Adam Buchbinder <adam.buchbinder@...il.com>,
Alex Bennée <alex.bennee@...aro.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Andrey Ryabinin <ryabinin.a.a@...il.com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Christoffer Dall <christoffer.dall@...aro.org>,
Daniel Thompson <daniel.thompson@...aro.org>,
Dave P Martin <Dave.Martin@....com>,
Jens Wiklander <jens.wiklander@...aro.org>,
Jisheng Zhang <jszhang@...vell.com>,
John Blackwood <john.blackwood@...r.com>,
Mark Rutland <mark.rutland@....com>,
Petr Mladek <pmladek@...e.com>,
Robin Murphy <robin.murphy@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Vladimir Murzin <Vladimir.Murzin@....com>,
Yang Shi <yang.shi@...aro.org>,
Zi Shen Lim <zlim.lnx@...il.com>,
yalin wang <yalin.wang2010@...il.com>,
Mark Brown <broonie@...nel.org>
Subject: [PATCH v15 09/10] arm64: Add kernel return probes support (kretprobes)
From: Sandeepa Prabhu <sandeepa.s.prabhu@...il.com>
The pre-handler of this special 'trampoline' kprobe executes the return
probe handler functions and restores original return address in ELR_EL1.
This way the saved pt_regs still hold the original register context to be
carried back to the probed kernel function.
Signed-off-by: Sandeepa Prabhu <sandeepa.s.prabhu@...il.com>
Signed-off-by: David A. Long <dave.long@...aro.org>
Acked-by: Masami Hiramatsu <mhiramat@...nel.org>
---
arch/arm64/Kconfig | 1 +
arch/arm64/kernel/probes/kprobes.c | 90 +++++++++++++++++++++++++++++++++++++-
2 files changed, 90 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1f7d644..6af0e2e 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -89,6 +89,7 @@ config ARM64
select HAVE_RCU_TABLE_FREE
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_KPROBES
+ select HAVE_KRETPROBES if HAVE_KPROBES
select IOMMU_DMA if IOMMU_SUPPORT
select IRQ_DOMAIN
select IRQ_FORCED_THREADING
diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index be1f074..9c70e88 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -578,7 +578,95 @@ bool arch_within_kprobe_blacklist(unsigned long addr)
void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
{
- return NULL;
+ struct kretprobe_instance *ri = NULL;
+ struct hlist_head *head, empty_rp;
+ struct hlist_node *tmp;
+ unsigned long flags, orig_ret_address = 0;
+ unsigned long trampoline_address =
+ (unsigned long)&kretprobe_trampoline;
+ kprobe_opcode_t *correct_ret_addr = NULL;
+
+ 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
+ * return probes installed on them, and/or more than one
+ * return probe was registered for a target function.
+ *
+ * We can handle this because:
+ * - instances are always pushed into the head of the list
+ * - when multiple return probes are registered for the same
+ * function, the (chronologically) first instance's ret_addr
+ * will be the real return address, and all the rest will
+ * point to kretprobe_trampoline.
+ */
+ hlist_for_each_entry_safe(ri, tmp, head, hlist) {
+ if (ri->task != current)
+ /* another task is sharing our hash bucket */
+ continue;
+
+ orig_ret_address = (unsigned long)ri->ret_addr;
+
+ 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);
+
+ correct_ret_addr = ri->ret_addr;
+ hlist_for_each_entry_safe(ri, tmp, head, hlist) {
+ if (ri->task != current)
+ /* another task is sharing our hash bucket */
+ continue;
+
+ orig_ret_address = (unsigned long)ri->ret_addr;
+ if (ri->rp && ri->rp->handler) {
+ __this_cpu_write(current_kprobe, &ri->rp->kp);
+ get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
+ ri->ret_addr = correct_ret_addr;
+ ri->rp->handler(ri, regs);
+ __this_cpu_write(current_kprobe, NULL);
+ }
+
+ 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_hash_unlock(current, &flags);
+
+ hlist_for_each_entry_safe(ri, 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)
+{
+ ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
+
+ /* replace return addr (x30) with trampoline */
+ regs->regs[30] = (long)&kretprobe_trampoline;
+}
+
+int __kprobes arch_trampoline_kprobe(struct kprobe *p)
+{
+ return 0;
}
int __init arch_init_kprobes(void)
--
2.5.0
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