Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1403806 > unrolled thread

[RFC PATCH v2 1/3] arch/powerpc : Add detour buffer support for optprobes

Started byAnju T <anju@linux.vnet.ibm.com>
First post2016-05-19 17:20 +0200
Last post2016-05-30 11:00 +0200
Articles 4 — 3 participants

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  [RFC PATCH v2 1/3] arch/powerpc : Add detour buffer support for optprobes Anju T <anju@linux.vnet.ibm.com> - 2016-05-19 17:20 +0200
    Re: [RFC PATCH v2 1/3] arch/powerpc : Add detour buffer support for  optprobes Madhavan Srinivasan <maddy@linux.vnet.ibm.com> - 2016-05-24 12:20 +0200
    Re: [RFC PATCH v2 1/3] arch/powerpc : Add detour buffer support for  optprobes "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2016-05-24 13:20 +0200
    Re: [RFC PATCH v2 1/3] arch/powerpc : Add detour buffer support for  optprobes "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2016-05-30 11:00 +0200

#1403806 — [RFC PATCH v2 1/3] arch/powerpc : Add detour buffer support for optprobes

FromAnju T <anju@linux.vnet.ibm.com>
Date2016-05-19 17:20 +0200
Subject[RFC PATCH v2 1/3] arch/powerpc : Add detour buffer support for optprobes
Message-ID<rAxTX-1sm-11@gated-at.bofh.it>
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@linux.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

[toc] | [next] | [standalone]

#1406030 — Re: [RFC PATCH v2 1/3] arch/powerpc : Add detour buffer support for optprobes

FromMadhavan Srinivasan <maddy@linux.vnet.ibm.com>
Date2016-05-24 12:20 +0200
SubjectRe: [RFC PATCH v2 1/3] arch/powerpc : Add detour buffer support for optprobes
Message-ID<rChBn-1Ye-13@gated-at.bofh.it>
In reply to#1403806

On Thursday 19 May 2016 08:40 PM, Anju T wrote:
> 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@linux.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

Can we replace "65536" with SLOT_SIZE?

> +.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)

We are missing _CCR (CR register)?

Why tab space for the comment? and
a new line before the command will be good

> +	/* 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
same here.

> +	/* 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

Same here and also rest of the patch

> +.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

Again missing CR.

> +	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:

[toc] | [prev] | [next] | [standalone]

#1406070 — Re: [RFC PATCH v2 1/3] arch/powerpc : Add detour buffer support for optprobes

From"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Date2016-05-24 13:20 +0200
SubjectRe: [RFC PATCH v2 1/3] arch/powerpc : Add detour buffer support for optprobes
Message-ID<rCixs-2xY-3@gated-at.bofh.it>
In reply to#1403806
On 2016/05/19 08:40PM, Anju T wrote:
> 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@linux.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)

I think this will not work. Looking through the code, I don't see us 
saving/restoring CFAR across interrupts.

Also, per the ISA:
"The Come-From Address Register (CFAR) is a 64-bit
register. When an rfebb, rfid, or rfscv instruction is
executed, the register is set to the effective address of
the instruction."

So, it looks like we actually can't save/restore it anyway.

Regardless, NIP is the same as the kprobe'd address, so you should be 
able to either use immediate loads or load the address from kprobe 
structure.


- Naveen

[toc] | [prev] | [next] | [standalone]

#1408886 — Re: [RFC PATCH v2 1/3] arch/powerpc : Add detour buffer support for optprobes

From"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Date2016-05-30 11:00 +0200
SubjectRe: [RFC PATCH v2 1/3] arch/powerpc : Add detour buffer support for optprobes
Message-ID<rErdf-1TA-17@gated-at.bofh.it>
In reply to#1403806
On 2016/05/24 03:45PM, Madhavan Srinivasan wrote:
> 
> 
> On Thursday 19 May 2016 08:40 PM, Anju T wrote:
> > 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@linux.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>
> > +

You should also add an align directive here:

.align 2

> > +.global optinsn_slot
> > +optinsn_slot:
> > +	/* Reserve an area to allocate slots for detour buffer */
> > +	.space	65536
> 
> Can we replace "65536" with SLOT_SIZE?

Yes, a macro will be good to have.

> 
> > +.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)
> 
> We are missing _CCR (CR register)?

Yes, and I think we need to ensure we fill reasonable values for all 
registers in pt_regs including softe (from paca), orig_gpr3 (0?) and 
result (0).

> 
> Why tab space for the comment? and
> a new line before the command will be good

... new line before *each section* will be good :)

> 
> > +	/* Pass parameters for optimized_callback */
> > +.global optprobe_template_op_address1
> > +optprobe_template_op_address1:

So, the general style is to align labels at the start of a line and to 
align everything else as per the code indentation.

In this case though, I think it's best to use a macro for better 
readability. Something like:

#define _GLOB(name)	.global name;		\
			name:


- Naveen

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web