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Message-Id: <1473240792-10596-2-git-send-email-anju@linux.vnet.ibm.com>
Date: Wed, 7 Sep 2016 15:03:10 +0530
From: Anju T Sudhakar <anju@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Cc: ananth@...ibm.com, naveen.n.rao@...ux.vnet.ibm.com,
paulus@...ba.org, srikar@...ux.vnet.ibm.com,
benh@...nel.crashing.org, mpe@...erman.id.au,
hemant@...ux.vnet.ibm.com, mahesh@...ux.vnet.ibm.com,
mhiramat@...nel.org, Anju T Sudhakar <anju@...ux.vnet.ibm.com>
Subject: [PATCH 1/3] arch/powerpc : Add detour buffer support for optprobes
Detour buffer contains instructions to create an in memory pt_regs.
After the execution of prehandler a call is made for instruction emulation.
The NIP is decided after the probed instruction is executed. Hence a branch
instruction is created to the NIP returned by emulate_step().
Instruction slot for detour buffer is allocated from the reserved area.
For the time being 64KB is reserved in memory for this purpose.
Signed-off-by: Anju T Sudhakar <anju@...ux.vnet.ibm.com>
---
arch/powerpc/include/asm/kprobes.h | 24 +++++++
arch/powerpc/kernel/optprobes_head.S | 119 +++++++++++++++++++++++++++++++++++
2 files changed, 143 insertions(+)
create mode 100644 arch/powerpc/kernel/optprobes_head.S
diff --git a/arch/powerpc/include/asm/kprobes.h b/arch/powerpc/include/asm/kprobes.h
index 2c9759bd..2109ce03 100644
--- a/arch/powerpc/include/asm/kprobes.h
+++ b/arch/powerpc/include/asm/kprobes.h
@@ -38,7 +38,25 @@ struct pt_regs;
struct kprobe;
typedef ppc_opcode_t kprobe_opcode_t;
+
+extern kprobe_opcode_t optinsn_slot;
+/* Optinsn template address */
+extern kprobe_opcode_t optprobe_template_entry[];
+extern kprobe_opcode_t optprobe_template_call_handler[];
+extern kprobe_opcode_t optprobe_template_call_emulate[];
+extern kprobe_opcode_t optprobe_template_ret[];
+extern kprobe_opcode_t optprobe_template_insn[];
+extern kprobe_opcode_t optprobe_template_kp_addr[];
+extern kprobe_opcode_t optprobe_template_op_address1[];
+extern kprobe_opcode_t optprobe_template_end[];
+
#define MAX_INSN_SIZE 1
+#define MAX_OPTIMIZED_LENGTH 4
+#define MAX_OPTINSN_SIZE \
+ (((unsigned long)&optprobe_template_end - \
+ (unsigned long)&optprobe_template_entry) / \
+ sizeof(kprobe_opcode_t))
+#define RELATIVEJUMP_SIZE 4
#ifdef PPC64_ELF_ABI_v2
/* PPC64 ABIv2 needs local entry point */
@@ -124,6 +142,12 @@ struct kprobe_ctlblk {
struct prev_kprobe prev_kprobe;
};
+struct arch_optimized_insn {
+ kprobe_opcode_t copied_insn[1];
+ /* detour buffer */
+ kprobe_opcode_t *insn;
+};
+
extern int kprobe_exceptions_notify(struct notifier_block *self,
unsigned long val, void *data);
extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
diff --git a/arch/powerpc/kernel/optprobes_head.S b/arch/powerpc/kernel/optprobes_head.S
new file mode 100644
index 0000000..73db1df
--- /dev/null
+++ b/arch/powerpc/kernel/optprobes_head.S
@@ -0,0 +1,119 @@
+/*
+ * Code to prepare detour buffer for optprobes in Kernel.
+ *
+ * Copyright 2016, Anju T, IBM Corp.
+ *
+ * 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 the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <asm/ppc_asm.h>
+#include <asm/ptrace.h>
+#include <asm/asm-offsets.h>
+
+#define OPT_SLOT_SIZE 65536
+
+.balign 2
+.global optinsn_slot
+optinsn_slot:
+ /* Reserve an area to allocate slots for detour buffer */
+ .space OPT_SLOT_SIZE
+
+/* Create an in-memory pt_regs */
+.global optprobe_template_entry
+optprobe_template_entry:
+ stdu r1,-INT_FRAME_SIZE(r1)
+ SAVE_GPR(0,r1)
+ /* Save the previous SP into stack */
+ addi r0,r1,INT_FRAME_SIZE
+ std r0,GPR1(r1)
+ SAVE_10GPRS(2,r1)
+ SAVE_10GPRS(12,r1)
+ SAVE_10GPRS(22,r1)
+ /* Save SPRS */
+ mfmsr r5
+ std r5,_MSR(r1)
+ li r5,0
+ std r5,ORIG_GPR3(r1)
+ std r5,_TRAP(r1)
+ std r5,RESULT(r1)
+ mfctr r5
+ std r5,_CTR(r1)
+ mflr r5
+ std r5,_LINK(r1)
+ mfspr r5,SPRN_XER
+ std r5,_XER(r1)
+ mfcr r5
+ std r5,_CCR(r1)
+ lbz r5,PACASOFTIRQEN(r13)
+ std r5,SOFTE(r1)
+ mfdar r5
+ std r5,_DAR(r1)
+ mfdsisr r5
+ std r5,_DSISR(r1)
+
+/* Save p->addr into stack */
+.global optprobe_template_kp_addr
+optprobe_template_kp_addr:
+ nop
+ nop
+ nop
+ nop
+ nop
+ std r3,_NIP(r1)
+
+/* Pass parameters for optimized_callback */
+.global optprobe_template_op_address1
+optprobe_template_op_address1:
+ nop
+ nop
+ nop
+ nop
+ nop
+ addi r4,r1,STACK_FRAME_OVERHEAD
+
+/* Branch to optimized_callback() */
+.global optprobe_template_call_handler
+optprobe_template_call_handler:
+ nop
+ /* Pass parameters for instruction emulation */
+ addi r3,r1,STACK_FRAME_OVERHEAD
+.global optprobe_template_insn
+optprobe_template_insn:
+ nop
+ nop
+
+/* Branch to instruction emulation */
+.global optprobe_template_call_emulate
+optprobe_template_call_emulate:
+ nop
+ /* Restore the registers */
+ ld r5,_MSR(r1)
+ mtmsr r5
+ ld r5,_CTR(r1)
+ mtctr r5
+ ld r5,_LINK(r1)
+ mtlr r5
+ ld r5,_XER(r1)
+ mtxer r5
+ ld r5,_CCR(r1)
+ mtcr r5
+ ld r5,_DAR(r1)
+ mtdar r5
+ ld r5,_DSISR(r1)
+ mtdsisr r5
+ REST_GPR(0,r1)
+ REST_10GPRS(2,r1)
+ REST_10GPRS(12,r1)
+ REST_10GPRS(22,r1)
+ /* Restore the previous SP */
+ addi r1,r1,INT_FRAME_SIZE
+
+/* Jump back to the normal workflow from trampoline */
+.global optprobe_template_ret
+optprobe_template_ret:
+ nop
+.global optprobe_template_end
+optprobe_template_end:
--
1.8.3.1
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