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Message-Id: <1463670640-25701-2-git-send-email-anju@linux.vnet.ibm.com>
Date: Thu, 19 May 2016 20:40:38 +0530
From: Anju T <anju@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Cc: anju@...ux.vnet.ibm.com, 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
Subject: [RFC PATCH v2 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 <anju@...ux.vnet.ibm.com>
---
arch/powerpc/include/asm/kprobes.h | 25 ++++++++
arch/powerpc/kernel/optprobes_head.S | 108 +++++++++++++++++++++++++++++++++++
2 files changed, 133 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 039b583..3e4c998 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_branch[];
+extern kprobe_opcode_t optprobe_template_ret[];
+extern kprobe_opcode_t optprobe_template_insn[];
+extern kprobe_opcode_t optprobe_template_op_address1[];
+extern kprobe_opcode_t optprobe_template_op_address2[];
+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)
+#define RELATIVEJUMP_SIZE 4
#ifdef CONFIG_PPC64
#if defined(_CALL_ELF) && _CALL_ELF == 2
@@ -129,5 +147,12 @@ struct kprobe_ctlblk {
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);
+
+struct arch_optimized_insn {
+ kprobe_opcode_t copied_insn[1];
+ /* detour buffer */
+ kprobe_opcode_t *insn;
+};
+
#endif /* __KERNEL__ */
#endif /* _ASM_POWERPC_KPROBES_H */
diff --git a/arch/powerpc/kernel/optprobes_head.S b/arch/powerpc/kernel/optprobes_head.S
new file mode 100644
index 0000000..ce32aec
--- /dev/null
+++ b/arch/powerpc/kernel/optprobes_head.S
@@ -0,0 +1,108 @@
+/*
+ * 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>
+
+.global optinsn_slot
+optinsn_slot:
+ /* Reserve an area to allocate slots for detour buffer */
+ .space 65536
+.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 0,GPR1(r1)
+ SAVE_2GPRS(2,r1)
+ SAVE_8GPRS(4,r1)
+ SAVE_10GPRS(12,r1)
+ SAVE_10GPRS(22,r1)
+ /* Save SPRS */
+ mfcfar r5
+ std r5,_NIP(r1)
+ mfmsr r5
+ std r5,_MSR(r1)
+ mfctr r5
+ std r5,_CTR(r1)
+ mflr r5
+ std r5,_LINK(r1)
+ mfspr r5,SPRN_XER
+ std r5,_XER(r1)
+ li r5,0
+ std r5,_TRAP(r1)
+ mfdar r5
+ std r5,_DAR(r1)
+ mfdsisr r5
+ std r5,_DSISR(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 the prehandler */
+.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
+.global optprobe_template_op_address2
+optprobe_template_op_address2:
+ nop
+ nop
+ nop
+ nop
+ nop
+ addi r4,r1,STACK_FRAME_OVERHEAD
+ /* Branch to create_return_branch() function */
+.global optprobe_template_ret_branch
+optprobe_template_ret_branch:
+ 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,_DAR(r1)
+ mtdar r5
+ ld r5,_DSISR(r1)
+ mtdsisr r5
+ REST_GPR(0,r1)
+ REST_2GPRS(2,r1)
+ REST_8GPRS(4,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:
--
2.1.0
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