Subject: Re: [PATCH v7 23/28] powerpc: Add prefixed instructions to instruction data type

From: Alistair Popple <[email-masked]>
Date: Tue, 05 May 2020 16:04:07 +1000

When reviewing earlier patches in this series I assumed the data type would 
eventually change size (on PPC64 at least) so I was looking for any possible 
side effects this may cause, but I didn't notice any so I think this should be 
ok:

Reviewed-by: Alistair Popple <[email-masked]>

However I haven't dug deeply enough into the optprobes code to fully 
understand/comment on the changes there (although they look correct afaict).

On Friday, 1 May 2020 1:42:15 PM AEST 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 <[email-masked]>
> ---
> 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
> v6:  - Return false instead of 0 in ppc_inst_prefixed()
>      - Fix up types for ppc32 so it compiles
>      - remove ppc_inst_write()
>      - __patching_instruction(): move flush out of condition
> ---
>  arch/powerpc/include/asm/inst.h      | 68 +++++++++++++++++++++++++---
>  arch/powerpc/include/asm/kprobes.h   |  2 +-
>  arch/powerpc/include/asm/uaccess.h   | 32 ++++++++++++-
>  arch/powerpc/include/asm/uprobes.h   |  2 +-
>  arch/powerpc/kernel/optprobes.c      | 42 +++++++++--------
>  arch/powerpc/kernel/optprobes_head.S |  3 ++
>  arch/powerpc/lib/code-patching.c     | 13 ++++--
>  arch/powerpc/lib/feature-fixups.c    |  5 +-
>  arch/powerpc/lib/inst.c              | 40 ++++++++++++++++
>  arch/powerpc/lib/sstep.c             |  4 +-
>  arch/powerpc/xmon/xmon.c             |  4 +-
>  arch/powerpc/xmon/xmon_bpts.S        |  2 +
>  12 files changed, 180 insertions(+), 37 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/inst.h
> b/arch/powerpc/include/asm/inst.h index 2f3c9d5bcf7c..1e743635c214 100644
> --- a/arch/powerpc/include/asm/inst.h
> +++ b/arch/powerpc/include/asm/inst.h
> @@ -8,23 +8,72 @@
> 
>  struct ppc_inst {
>  	u32 val;
> +#ifdef __powerpc64__
> +	u32 suffix;
> +#endif /* __powerpc64__ */
>  } __packed;
> 
> -#define ppc_inst(x) ((struct ppc_inst){ .val = x })
> -
>  static inline u32 ppc_inst_val(struct ppc_inst x)
>  {
>  	return x.val;
>  }
> 
> -static inline int ppc_inst_len(struct ppc_inst x)
> +static inline int ppc_inst_primary_opcode(struct ppc_inst x)
>  {
> -	return sizeof(struct ppc_inst);
> +	return ppc_inst_val(x) >> 26;
>  }
> 
> -static inline int ppc_inst_primary_opcode(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 ppc_inst_val(x) >> 26;
> +	return x.suffix;
> +}
> +
> +static inline bool ppc_inst_prefixed(struct ppc_inst x)
> +{
> +	return (ppc_inst_primary_opcode(x) == 1) && ppc_inst_suffix(x) != 0xff;
> +}
> +
> +static inline struct ppc_inst ppc_inst_swab(struct ppc_inst x)
> +{
> +	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;
> +
> +	val = *(u32 *)ptr;
> +	if ((val >> 26) == 1) {
> +		suffix = *((u32 *)ptr + 1);
> +		return ppc_inst_prefix(val, suffix);
> +	} else {
> +		return ppc_inst(val);
> +	}
> +}
> +
> +static inline bool ppc_inst_equal(struct ppc_inst x, struct ppc_inst y)
> +{
> +	return *(u64 *)&x == *(u64 *)&y;
> +}
> +
> +#else
> +
> +#define ppc_inst(x) ((struct ppc_inst){ .val = x })
> +
> +static inline bool ppc_inst_prefixed(struct ppc_inst x)
> +{
> +	return false;
> +}
> +
> +static inline u32 ppc_inst_suffix(struct ppc_inst x)
> +{
> +	return 0;
>  }
> 
>  static inline struct ppc_inst ppc_inst_swab(struct ppc_inst x)
> @@ -42,6 +91,13 @@ static inline bool ppc_inst_equal(struct ppc_inst x,
> struct ppc_inst y) return ppc_inst_val(x) == ppc_inst_val(y);
>  }
> 
> +#endif /* __powerpc64__ */
> +
> +static inline int ppc_inst_len(struct ppc_inst x)
> +{
> +	return (ppc_inst_prefixed(x)) ? 8  : 4;
> +}
> +
>  int probe_user_read_inst(struct ppc_inst *inst,
>  			 struct ppc_inst *nip);
>  int probe_kernel_read_inst(struct ppc_inst *inst,
> 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..12e52aa179b6
> 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -105,11 +105,41 @@ 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)))
> 
> +#ifdef __powerpc64__
> +#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;					\
> +})
> +#else
>  #define __get_user_instr(x, ptr) \
>  	__get_user_nocheck((x).val, (u32 *)(ptr), sizeof(u32), true)
> -
>  #define __get_user_instr_inatomic(x, ptr) \
>  	__get_user_nosleep((x).val, (u32 *)(ptr), sizeof(u32))
> +#endif
> +
>  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 d704f9598f48..a67c5288cf50 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),
> +			       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/lib/code-patching.c
> b/arch/powerpc/lib/code-patching.c index 5b2f66d06b1e..b32fa707725e 100644
> --- a/arch/powerpc/lib/code-patching.c
> +++ b/arch/powerpc/lib/code-patching.c
> @@ -24,13 +24,18 @@ 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;
> +	if (!ppc_inst_prefixed(instr)) {
> +		__put_user_asm(ppc_inst_val(instr), patch_addr, err, "stw");
> +		if (err)
> +			return err;
> +	} 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));
> -
>  	return 0;
>  }
> 
> diff --git a/arch/powerpc/lib/feature-fixups.c
> b/arch/powerpc/lib/feature-fixups.c index f4845e740338..243011f85287 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/inst.c b/arch/powerpc/lib/inst.c
> index 08dedd927268..71101791edcc 100644
> --- a/arch/powerpc/lib/inst.c
> +++ b/arch/powerpc/lib/inst.c
> @@ -6,6 +6,45 @@
>  #include <linux/uaccess.h>
>  #include <asm/inst.h>
> 
> +#ifdef __powerpc64__
> +int probe_user_read_inst(struct ppc_inst *inst,
> +			 struct ppc_inst *nip)
> +{
> +	unsigned int val, suffix;
> +	int err;
> +
> +	err = probe_user_read(&val, nip, sizeof(val));
> +	if (err)
> +		return err;
> +	if ((val >> 26) == 1) {
> +		err = probe_user_read(&suffix, (void *)nip+4,
> +				      sizeof(unsigned int));
> +		*inst = ppc_inst_prefix(val, suffix);
> +	} else {
> +		*inst = ppc_inst(val);
> +	}
> +	return err;
> +}
> +
> +int probe_kernel_read_inst(struct ppc_inst *inst,
> +			   struct ppc_inst *src)
> +{
> +	unsigned int val, suffix;
> +	int err;
> +
> +	err = probe_kernel_read(&val, src, sizeof(val));
> +	if (err)
> +		return err;
> +	if ((val >> 26) == 1) {
> +		err = probe_kernel_read(&suffix, (void *)src+4,
> +				      sizeof(unsigned int));
> +		*inst = ppc_inst_prefix(val, suffix);
> +	} else {
> +		*inst = ppc_inst(val);
> +	}
> +	return err;
> +}
> +#else
>  int probe_user_read_inst(struct ppc_inst *inst,
>  			 struct ppc_inst *nip)
>  {
> @@ -27,3 +66,4 @@ int probe_kernel_read_inst(struct ppc_inst *inst,
>  	*inst = ppc_inst(val);
>  	return err;
>  }
> +#endif /* __powerpc64__ */
> diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
> index 95a56bb1ba3f..ecd756c346fd 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);
> +
>  	op->type = COMPUTE;
> 
>  	opcode = ppc_inst_primary_opcode(instr);
> diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
> index fb2563079046..1d6e66eb2dab 100644
> --- a/arch/powerpc/xmon/xmon.c
> +++ b/arch/powerpc/xmon/xmon.c
> @@ -758,8 +758,8 @@ 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;
>  	}
> diff --git a/arch/powerpc/xmon/xmon_bpts.S b/arch/powerpc/xmon/xmon_bpts.S
> index f3ad0ab50854..69726814cd27 100644
> --- a/arch/powerpc/xmon/xmon_bpts.S
> +++ b/arch/powerpc/xmon/xmon_bpts.S
> @@ -4,6 +4,8 @@
>  #include <asm/asm-offsets.h>
>  #include "xmon_bpts.h"
> 
> +/* Prefixed instructions can not cross 64 byte boundaries */
> +.align 6
>  .global bpt_table
>  bpt_table:
>  	.space NBPTS * BPT_SIZE