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Subject: Re: [PATCH v5 18/21] powerpc64: Add prefixed instructions to
 instruction data type
From: Balamuruhan S <bala24@linux.ibm.com>
To: Jordan Niethe <jniethe5@gmail.com>, linuxppc-dev@lists.ozlabs.org
Date: Mon, 13 Apr 2020 17:34:50 +0530
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 <20200406080936.7180-19-jniethe5@gmail.com>
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On Mon, 2020-04-06 at 18:09 +1000, Jordan Niethe wrote:
> For powerpc64, redefine the ppc_inst type so both word and prefixed
> instructions can be represented. On powerpc32 the type will remain the
> same.  Update places which had assumed instructions to be 4 bytes long.
> 
> Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> ---
> v4: New to series
> v5:  - Distinguish normal instructions from prefixed instructions with a
>        0xff marker for the suffix.
>      - __patch_instruction() using std for prefixed instructions
> ---
>  arch/powerpc/include/asm/inst.h      | 71 ++++++++++++++++++++++++++--
>  arch/powerpc/include/asm/kprobes.h   |  2 +-
>  arch/powerpc/include/asm/uaccess.h   | 31 ++++++++++--
>  arch/powerpc/include/asm/uprobes.h   |  2 +-
>  arch/powerpc/kernel/optprobes.c      | 42 ++++++++--------
>  arch/powerpc/kernel/optprobes_head.S |  3 ++
>  arch/powerpc/kernel/trace/ftrace.c   | 26 +++++++++-
>  arch/powerpc/lib/code-patching.c     | 19 +++++---
>  arch/powerpc/lib/feature-fixups.c    |  5 +-
>  arch/powerpc/lib/sstep.c             |  4 +-
>  arch/powerpc/xmon/xmon.c             |  6 +--
>  arch/powerpc/xmon/xmon_bpts.S        |  4 +-
>  12 files changed, 171 insertions(+), 44 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/inst.h
> b/arch/powerpc/include/asm/inst.h
> index 70b37a35a91a..7e23e7146c66 100644
> --- a/arch/powerpc/include/asm/inst.h
> +++ b/arch/powerpc/include/asm/inst.h
> @@ -8,23 +8,67 @@
>  
>  struct ppc_inst {
>          u32 val;
> +#ifdef __powerpc64__
> +        u32 suffix;
> +#endif /* __powerpc64__ */
>  } __packed;
>  
> -#define ppc_inst(x) ((struct ppc_inst){ .val = x })
> +static inline int ppc_inst_opcode(struct ppc_inst x)
> +{
> +	return x.val >> 26;


why don't we wrap here and in `ppc_inst_opcode()` in patch 9 using
`ppc_inst_val()` ?


> +}
>  
>  static inline u32 ppc_inst_val(struct ppc_inst x)


There is another same definition below for the same function in
#else part of __powerpc64__ ifdef.


>  {
>  	return x.val;
>  }
>  
> -static inline bool ppc_inst_len(struct ppc_inst x)
> +#ifdef __powerpc64__
> +#define ppc_inst(x) ((struct ppc_inst){ .val = (x), .suffix = 0xff })
> +
> +#define ppc_inst_prefix(x, y) ((struct ppc_inst){ .val = (x), .suffix = (y)
> })
> +
> +static inline u32 ppc_inst_suffix(struct ppc_inst x)
>  {
> -	return sizeof(struct ppc_inst);
> +	return x.suffix;
>  }
>  
> -static inline int ppc_inst_opcode(struct ppc_inst x)
> +static inline bool ppc_inst_prefixed(struct ppc_inst x) {
> +	return ((ppc_inst_val(x) >> 26) == 1) && ppc_inst_suffix(x) != 0xff;
> +}
> +
> +static inline struct ppc_inst ppc_inst_swab(struct ppc_inst x)
>  {
> -	return x.val >> 26;
> +	return ppc_inst_prefix(swab32(ppc_inst_val(x)),
> +			       swab32(ppc_inst_suffix(x)));
> +}
> +
> +static inline struct ppc_inst ppc_inst_read(const struct ppc_inst *ptr)
> +{
> +	u32 val, suffix = 0xff;
> +	val = *(u32 *)ptr;
> +	if ((val >> 26) == 1)
> +		suffix = *((u32 *)ptr + 1);
> +	return ppc_inst_prefix(val, suffix);
> +}
> +
> +static inline void ppc_inst_write(struct ppc_inst *ptr, struct ppc_inst x)
> +{
> +	if (ppc_inst_prefixed(x)) {
> +		*(u32 *)ptr = x.val;
> +		*((u32 *)ptr + 1) = x.suffix;
> +	} else {
> +		*(u32 *)ptr = x.val;


can we wrap here as well with `ppc_inst_val()` and `ppc_inst_suffix()` ?


> +	}
> +}
> +
> +#else
> +
> +#define ppc_inst(x) ((struct ppc_inst){ .val = x })
> +
> +static inline bool ppc_inst_prefixed(ppc_inst x)
> +{
> +	return 0;


Is it return !!0 or return false ?


>  }
>  
>  static inline struct ppc_inst ppc_inst_swab(struct ppc_inst x)
> @@ -32,14 +76,31 @@ static inline struct ppc_inst ppc_inst_swab(struct
> ppc_inst x)
>  	return ppc_inst(swab32(ppc_inst_val(x)));
>  }
>  
> +static inline u32 ppc_inst_val(struct ppc_inst x)


[...] duplicate definition that is defined outside __powerpc64__ above.


> +{
> +	return x.val;
> +}
> +
>  static inline struct ppc_inst ppc_inst_read(const struct ppc_inst *ptr)
>  {
>  	return *ptr;
>  }
>  
> +static inline void ppc_inst_write(struct ppc_inst *ptr, struct ppc_inst x)
> +{
> +	*ptr = x;
> +}
> +
> +#endif /* __powerpc64__ */
> +
>  static inline bool ppc_inst_equal(struct ppc_inst x, struct ppc_inst y)
>  {
>  	return !memcmp(&x, &y, sizeof(struct ppc_inst));
>  }
>  
> +static inline int ppc_inst_len(struct ppc_inst x)
> +{
> +	return (ppc_inst_prefixed(x)) ? 8  : 4;
> +}
> +
>  #endif /* _ASM_INST_H */
> diff --git a/arch/powerpc/include/asm/kprobes.h
> b/arch/powerpc/include/asm/kprobes.h
> index 66b3f2983b22..4fc0e15e23a5 100644
> --- a/arch/powerpc/include/asm/kprobes.h
> +++ b/arch/powerpc/include/asm/kprobes.h
> @@ -43,7 +43,7 @@ extern kprobe_opcode_t optprobe_template_ret[];
>  extern kprobe_opcode_t optprobe_template_end[];
>  
>  /* Fixed instruction size for powerpc */
> -#define MAX_INSN_SIZE		1
> +#define MAX_INSN_SIZE		2
>  #define MAX_OPTIMIZED_LENGTH	sizeof(kprobe_opcode_t)	/* 4 bytes */
>  #define MAX_OPTINSN_SIZE	(optprobe_template_end -
> optprobe_template_entry)
>  #define RELATIVEJUMP_SIZE	sizeof(kprobe_opcode_t)	/* 4 bytes */
> diff --git a/arch/powerpc/include/asm/uaccess.h
> b/arch/powerpc/include/asm/uaccess.h
> index c0a35e4586a5..5a3f486ddf02 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -105,11 +105,34 @@ static inline int __access_ok(unsigned long addr,
> unsigned long size,
>  #define __put_user_inatomic(x, ptr) \
>  	__put_user_nosleep((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)))
>  
> -#define __get_user_instr(x, ptr) \
> -	__get_user_nocheck((x).val, (u32 *)(ptr), sizeof(u32), true)
> +#define __get_user_instr(x, ptr)			\
> +({							\
> +	long __gui_ret = 0;				\
> +	unsigned int prefix, suffix;			\
> +	__gui_ret = __get_user(prefix, (unsigned int __user *)ptr);		
> \
> +	if (!__gui_ret && (prefix >> 26) == 1) {	\
> +		__gui_ret = __get_user(suffix, (unsigned int __user *)ptr + 1);
> 	\
> +		(x) = ppc_inst_prefix(prefix, suffix);	\
> +	} else {					\
> +		(x) = ppc_inst(prefix);			\
> +	}						\
> +	__gui_ret;					\
> +})
> +
> +#define __get_user_instr_inatomic(x, ptr)		\
> +({							\
> +	long __gui_ret = 0;				\
> +	unsigned int prefix, suffix;			\
> +	__gui_ret = __get_user_inatomic(prefix, (unsigned int __user *)ptr);	
> 	\
> +	if (!__gui_ret && (prefix >> 26) == 1) {	\
> +		__gui_ret = __get_user_inatomic(suffix, (unsigned int __user
> *)ptr + 1);	\
> +		(x) = ppc_inst_prefix(prefix, suffix);	\
> +	} else {					\
> +		(x) = ppc_inst(prefix);			\
> +	}						\
> +	__gui_ret;					\
> +})
>  
> -#define __get_user_instr_inatomic(x, ptr) \
> -	__get_user_nosleep((x).val, (u32 *)(ptr), sizeof(u32))
>  extern long __put_user_bad(void);
>  
>  /*
> diff --git a/arch/powerpc/include/asm/uprobes.h
> b/arch/powerpc/include/asm/uprobes.h
> index 7e3b329ba2d3..5bf65f5d44a9 100644
> --- a/arch/powerpc/include/asm/uprobes.h
> +++ b/arch/powerpc/include/asm/uprobes.h
> @@ -15,7 +15,7 @@
>  
>  typedef ppc_opcode_t uprobe_opcode_t;
>  
> -#define MAX_UINSN_BYTES		4
> +#define MAX_UINSN_BYTES		8
>  #define UPROBE_XOL_SLOT_BYTES	(MAX_UINSN_BYTES)
>  
>  /* The following alias is needed for reference from arch-agnostic code */
> diff --git a/arch/powerpc/kernel/optprobes.c
> b/arch/powerpc/kernel/optprobes.c
> index 684640b8fa2e..689daf430161 100644
> --- a/arch/powerpc/kernel/optprobes.c
> +++ b/arch/powerpc/kernel/optprobes.c
> @@ -159,38 +159,38 @@ void patch_imm32_load_insns(unsigned int val,
> kprobe_opcode_t *addr)
>  
>  /*
>   * Generate instructions to load provided immediate 64-bit value
> - * to register 'r3' and patch these instructions at 'addr'.
> + * to register 'reg' and patch these instructions at 'addr'.
>   */
> -void patch_imm64_load_insns(unsigned long val, kprobe_opcode_t *addr)
> +void patch_imm64_load_insns(unsigned long val, int reg, kprobe_opcode_t
> *addr)
>  {
> -	/* lis r3,(op)@highest */
> -	patch_instruction((struct ppc_inst *)addr, ppc_inst(PPC_INST_ADDIS |
> ___PPC_RT(3) |
> +	/* lis reg,(op)@highest */
> +	patch_instruction((struct ppc_inst *)addr, ppc_inst(PPC_INST_ADDIS |
> ___PPC_RT(reg) |
>  			  ((val >> 48) & 0xffff)));
>  	addr++;
>  
> -	/* ori r3,r3,(op)@higher */
> -	patch_instruction((struct ppc_inst *)addr, ppc_inst(PPC_INST_ORI |
> ___PPC_RA(3) |
> -			  ___PPC_RS(3) | ((val >> 32) & 0xffff)));
> +	/* ori reg,reg,(op)@higher */
> +	patch_instruction((struct ppc_inst *)addr, ppc_inst(PPC_INST_ORI |
> ___PPC_RA(reg) |
> +			  ___PPC_RS(reg) | ((val >> 32) & 0xffff)));
>  	addr++;
>  
> -	/* rldicr r3,r3,32,31 */
> -	patch_instruction((struct ppc_inst *)addr, ppc_inst(PPC_INST_RLDICR |
> ___PPC_RA(3) |
> -			  ___PPC_RS(3) | __PPC_SH64(32) | __PPC_ME64(31)));
> +	/* rldicr reg,reg,32,31 */
> +	patch_instruction((struct ppc_inst *)addr, ppc_inst(PPC_INST_RLDICR |
> ___PPC_RA(reg) |
> +			  ___PPC_RS(reg) | __PPC_SH64(32) | __PPC_ME64(31)));
>  	addr++;
>  
> -	/* oris r3,r3,(op)@h */
> -	patch_instruction((struct ppc_inst *)addr, ppc_inst(PPC_INST_ORIS |
> ___PPC_RA(3) |
> -			  ___PPC_RS(3) | ((val >> 16) & 0xffff)));
> +	/* oris reg,reg,(op)@h */
> +	patch_instruction((struct ppc_inst *)addr, ppc_inst(PPC_INST_ORIS |
> ___PPC_RA(reg) |
> +			  ___PPC_RS(reg) | ((val >> 16) & 0xffff)));
>  	addr++;
>  
> -	/* ori r3,r3,(op)@l */
> -	patch_instruction((struct ppc_inst *)addr, ppc_inst(PPC_INST_ORI |
> ___PPC_RA(3) |
> -			  ___PPC_RS(3) | (val & 0xffff)));
> +	/* ori reg,reg,(op)@l */
> +	patch_instruction((struct ppc_inst *)addr, ppc_inst(PPC_INST_ORI |
> ___PPC_RA(reg) |
> +			  ___PPC_RS(reg) | (val & 0xffff)));
>  }
>  
>  int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe
> *p)
>  {
> -	struct ppc_inst branch_op_callback, branch_emulate_step;
> +	struct ppc_inst branch_op_callback, branch_emulate_step, temp;
>  	kprobe_opcode_t *op_callback_addr, *emulate_step_addr, *buff;
>  	long b_offset;
>  	unsigned long nip, size;
> @@ -240,7 +240,7 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe
> *op, struct kprobe *p)
>  	 * Fixup the template with instructions to:
>  	 * 1. load the address of the actual probepoint
>  	 */
> -	patch_imm64_load_insns((unsigned long)op, buff + TMPL_OP_IDX);
> +	patch_imm64_load_insns((unsigned long)op, 3, buff + TMPL_OP_IDX);
>  
>  	/*
>  	 * 2. branch to optimized_callback() and emulate_step()
> @@ -271,7 +271,11 @@ int arch_prepare_optimized_kprobe(struct
> optimized_kprobe *op, struct kprobe *p)
>  	/*
>  	 * 3. load instruction to be emulated into relevant register, and
>  	 */
> -	patch_imm32_load_insns(*p->ainsn.insn, buff + TMPL_INSN_IDX);
> +	temp = ppc_inst_read((struct ppc_inst *)p->ainsn.insn);
> +	patch_imm64_load_insns(ppc_inst_val(temp) |
> +			       ((u64)ppc_inst_suffix(temp) << 32),


did we check building for ppc32 ?

I doubt we might hit build failure as `ppc_inst_suffix()` macro is not defined.


> +			       4,
> +			       buff + TMPL_INSN_IDX);
>  
>  	/*
>  	 * 4. branch back from trampoline
> diff --git a/arch/powerpc/kernel/optprobes_head.S
> b/arch/powerpc/kernel/optprobes_head.S
> index cf383520843f..ff8ba4d3824d 100644
> --- a/arch/powerpc/kernel/optprobes_head.S
> +++ b/arch/powerpc/kernel/optprobes_head.S
> @@ -94,6 +94,9 @@ optprobe_template_insn:
>  	/* 2, Pass instruction to be emulated in r4 */
>  	nop
>  	nop
> +	nop
> +	nop
> +	nop
>  
>  	.global optprobe_template_call_emulate
>  optprobe_template_call_emulate:
> diff --git a/arch/powerpc/kernel/trace/ftrace.c
> b/arch/powerpc/kernel/trace/ftrace.c
> index e78742613b36..16041a5c86d5 100644
> --- a/arch/powerpc/kernel/trace/ftrace.c
> +++ b/arch/powerpc/kernel/trace/ftrace.c
> @@ -41,11 +41,35 @@
>  #define	NUM_FTRACE_TRAMPS	8
>  static unsigned long ftrace_tramps[NUM_FTRACE_TRAMPS];
>  
> +#ifdef __powerpc64__
>  static long
>  probe_kernel_read_inst(struct ppc_inst *inst, const void *src)
>  {
> -	return probe_kernel_read((void *)inst, src, MCOUNT_INSN_SIZE);
> +	u32 val, suffix = 0;


don't we need to initialize suffix with 0xff ?


> +	long err;
> +
> +	err = probe_kernel_read((void *)&val,
> +				src, sizeof(val));
> +	if (err)
> +		return err;
> +
> +	if ((val >> 26) == 1)
> +		err = probe_kernel_read((void *)&suffix,
> +					src + 4, MCOUNT_INSN_SIZE);
> +	if (err)
> +		return err;
> +
> +	*inst = ppc_inst_prefix(val, suffix);
> +
> +	return 0;
>  }
> +#else
> +static long
> +probe_kernel_read_inst(struct ppc_inst *inst, const void *src)
> +{
> +	return probe_kernel_read((void *)inst, src, MCOUNT_INSN_SIZE)
> +}
> +#endif
>  
>  static struct ppc_inst
>  ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
> diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-
> patching.c
> index c329ad657302..b4007e03d8fa 100644
> --- a/arch/powerpc/lib/code-patching.c
> +++ b/arch/powerpc/lib/code-patching.c
> @@ -24,12 +24,19 @@ static int __patch_instruction(struct ppc_inst
> *exec_addr, struct ppc_inst instr
>  {
>  	int err = 0;
>  
> -	__put_user_asm(ppc_inst_val(instr), patch_addr, err, "stw");
> -	if (err)
> -		return err;
> -
> -	asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r" (patch_addr),
> -							    "r" (exec_addr));
> +	if (!ppc_inst_prefixed(instr)) {
> +		__put_user_asm(ppc_inst_val(instr), patch_addr, err, "stw");
> +		if (err)
> +			return err;
> +		asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r"
> (patch_addr),
> +								    "r"
> (exec_addr));
> +	} else {
> +		__put_user_asm((u64)ppc_inst_suffix(instr) << 32 |
> ppc_inst_val(instr), patch_addr, err, "std");
> +		if (err)
> +			return err;
> +		asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r"
> (patch_addr),
> +								    "r"
> (exec_addr));
> +	}


can we keep these 2 lines out of conditions as it remains to be the same ?

if (err)
	return err;
asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r" (patch_addr), "r"
(exec_addr));


>  
>  	return 0;
>  }
> diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-
> fixups.c
> index f00dd13b1c3c..5519cec83cc8 100644
> --- a/arch/powerpc/lib/feature-fixups.c
> +++ b/arch/powerpc/lib/feature-fixups.c
> @@ -84,12 +84,13 @@ static int patch_feature_section(unsigned long value,
> struct fixup_entry *fcur)
>  	src = alt_start;
>  	dest = start;
>  
> -	for (; src < alt_end; src++, dest++) {
> +	for (; src < alt_end; src = (void *)src +
> ppc_inst_len(ppc_inst_read(src)),
> +	     (dest = (void *)dest + ppc_inst_len(ppc_inst_read(dest)))) {
>  		if (patch_alt_instruction(src, dest, alt_start, alt_end))
>  			return 1;
>  	}
>  
> -	for (; dest < end; dest++)
> +	for (; dest < end; dest = (void *)dest +
> ppc_inst_len(ppc_inst(PPC_INST_NOP)))
>  		raw_patch_instruction(dest, ppc_inst(PPC_INST_NOP));
>  
>  	return 0;
> diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
> index 52ddd3122dc8..8b285bf11218 100644
> --- a/arch/powerpc/lib/sstep.c
> +++ b/arch/powerpc/lib/sstep.c
> @@ -1169,10 +1169,12 @@ int analyse_instr(struct instruction_op *op, const
> struct pt_regs *regs,
>  	unsigned long int imm;
>  	unsigned long int val, val2;
>  	unsigned int mb, me, sh;
> -	unsigned int word;
> +	unsigned int word, suffix;
>  	long ival;
>  
>  	word = ppc_inst_val(instr);
> +	suffix = ppc_inst_suffix(instr);


same here, I doubt it might break for ppc32.


-- Bala
> +
>  	op->type = COMPUTE;
>  
>  	opcode = word >> 26;
> diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
> index 6f3bcdcfc9c7..b704aebb099a 100644
> --- a/arch/powerpc/xmon/xmon.c
> +++ b/arch/powerpc/xmon/xmon.c
> @@ -761,8 +761,8 @@ static int xmon_bpt(struct pt_regs *regs)
>  
>  	/* Are we at the trap at bp->instr[1] for some bp? */
>  	bp = in_breakpoint_table(regs->nip, &offset);
> -	if (bp != NULL && offset == 4) {
> -		regs->nip = bp->address + 4;
> +	if (bp != NULL && (offset == 4 || offset == 8)) {
> +		regs->nip = bp->address + offset;
>  		atomic_dec(&bp->ref_count);
>  		return 1;
>  	}
> @@ -863,7 +863,7 @@ static struct bpt *in_breakpoint_table(unsigned long nip,
> unsigned long *offp)
>  	if (off >= sizeof(bpt_table))
>  		return NULL;
>  	*offp = off % BPT_SIZE;
> -	if (*offp != 0 && *offp != 4)
> +	if (*offp != 0 && *offp != 4 && *offp != 8)
>  		return NULL;
>  	return bpts + (off / BPT_SIZE);
>  }
> diff --git a/arch/powerpc/xmon/xmon_bpts.S b/arch/powerpc/xmon/xmon_bpts.S
> index ebb2dbc70ca8..09058eb6abbd 100644
> --- a/arch/powerpc/xmon/xmon_bpts.S
> +++ b/arch/powerpc/xmon/xmon_bpts.S
> @@ -3,6 +3,8 @@
>  #include <asm/asm-compat.h>
>  #include "xmon_bpts.h"
>  
> +/* Prefixed instructions can not cross 64 byte boundaries */
> +.align 6
>  .global bpt_table
>  bpt_table:
> -	.space NBPTS * 8
> +	.space NBPTS * 16