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Subject: Re: [PATCH v4 2/2] kernel/trace: Provide default impelentations
 defined in trace_probe_tmpl.h
To:     "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc:     rostedt@goodmis.org, arnd@arndb.de, linux-kernel@vger.kernel.org,
        linux-trace-kernel@vger.kernel.org, linux-arch@vger.kernel.org
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From:   Song Chen <chensong_2000@189.cn>
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Hi,

在 2023/1/3 18:33, Masami Hiramatsu (Google) 写道:
> On Fri, 30 Dec 2022 09:59:31 +0800
> Song Chen <chensong_2000@189.cn> wrote:
> 
>> Hi,
>>
>> 在 2022/12/29 17:30, Masami Hiramatsu (Google) 写道:
>>> On Wed, 28 Dec 2022 15:08:25 +0800
>>> Song Chen <chensong_2000@189.cn> wrote:
>>>
>>>> There are 7 function definitions in trace_probe_tmpl.h, they are:
>>>>
>>>> 1, process_fetch_insn
>>>
>>> Other functions except for this are OK for me.
>>> But I think this function should have different instance for kprobe
>>> and eprobe, because the passed 'void *rec' is completely different.
>>> For the kprobe's process_fetch_insn() will take a 'pt_regs *', on the
>>> other hand, the eprobe's process_fetch_insn() will take a
>>> 'ftrace_event_field *'.
>>> I also, don't want to expose get_event_field() function because
>>> it is only for the eprobes.
>>>
>>> What about making a new common function and call it in default case
>>> from both process_fetch_insn()? Your goal is reducing the redundant
>>> code, then it is enough to share only the common code. :)
>>>
>>> For example, in trace_probe_kernel.h,
>>>
>>> process_common_fetch_insn(struct fetch_insn *code, void *dest, void *base, unsigned long *val)
>>> {
>>> 	switch (code->op) {
>>> 	case FETCH_OP_IMM:
>>> 		*val = code->immediate;
>>> 		break;
>>> 	case FETCH_OP_COMM:
>>> 		*val = (unsigned long)current->comm;
>>> 		break;
>>> 	case FETCH_OP_DATA:
>>> 		*val = (unsigned long)code->data;
>>> 		break;
>>> 	default:
>>> 		return -EILSEQ;
>>> 	}
>>> 	return 0;
>>> }
>>>
>>> For kprobe events:
>>>
>>> process_fetch_insn(struct fetch_insn *code, void *rec, void *dest, void *base)
>>> {
>>> 	while (code->op == FETCH_NOP_SYMBOL)
>>> 		code++;
>>> 	switch (code->op) {
>>> 	case FETCH_OP_REG:
>>> 		val = regs_get_register(regs, code->param);
>>> 		...
>>> 	default:
>>> 		ret = process_common_fetch_insn(code, dest, base, &val);
>>> 		if (ret < 0)
>>> 			return ret;
>>> 	}
>>> 	...
>>> }
>>>
>>> For eprobe events:
>>>
>>> process_fetch_insn(struct fetch_insn *code, void *rec, void *dest, void *base)
>>> {
>>> 	while (code->op == FETCH_NOP_SYMBOL)
>>> 		code++;
>>> 	if (code->op == FETCH_OP_TP_ARG) {
>>> 		val = get_event_field(code, rec);
>>> 	} else {
>>> 		ret = process_common_fetch_insn(code, dest, base, &val);
>>> 		if (ret < 0)
>>> 			return ret;
>>> 	}
>>> 	...
>>> }
>>>
>>> You also don't see the error related to CONFIG_HAVE_REGS_AND_STACK_ACCESS_API. :)
>>>
>>> Thank you,
>>>
>>
>> Thanks a lot for the good idea and so specific demo code, i accept it
>> and will submit a new one based on it.
>>
>> If we think about it further, we can implement process_common_fetch_insn
>> in trace_probe_tmpl.h, uprobe can benefit from it as well, what do you
>> think? i will include it in the next submit and you can have a look.
> 
> Agreed. It sounds good to me. :)
> 
> Thank you!
> 

That's so kind, many thanks :)

Song

>>
>> Thanks again.
>>
>> Song
>>
>>>> 2, fetch_store_strlen
>>>> 3, fetch_store_string
>>>> 4, fetch_store_strlen_user
>>>> 5, fetch_store_string_user
>>>> 6, probe_mem_read
>>>> 7, probe_mem_read_user
>>>>
>>>> Every C file which includes trace_probe_tmpl.h has to implement them,
>>>> otherwise it gets warnings and errors. However, some of them are identical,
>>>> like kprobe and eprobe, as a result, there is a lot redundant code in those
>>>> 2 files.
>>>>
>>>> This patch would like to provide default behaviors for those functions
>>>> which kprobe and eprobe can share by just including trace_probe_kernel.h
>>>> with trace_probe_tmpl.h together.
>>>>
>>>> It removes redundant code, increases readability, and more importantly,
>>>> makes it easier to introduce a new feature based on trace probe
>>>> (it's possible).
>>>>
>>>> Signed-off-by: Song Chen <chensong_2000@189.cn>
>>>> Reported-by: kernel test robot <lkp@intel.com>
>>>>
>>>> ---
>>>> v2:
>>>> 1, reorganize patchset
>>>>
>>>> v3:
>>>> 1, mark nokprobe_inline for get_event_field
>>>> 2, remove warnings reported from kernel test robot
>>>> 3, fix errors reported from kernel test robot
>>>>
>>>> v4:
>>>> 1, reset changes in v3(2) and v3(3), they are not reasonable fix.
>>>> 2, I intended to introduce a new header file to exclude
>>>> trace_events_synth.c out of the patch. However, after looking
>>>> further, i found the errors in [1] are introduced by this patch,
>>>> but the warning in [1] are not. The errors can be fixed by adding
>>>> "#ifdef CONFIG_HAVE_REGS_AND_STACK_ACCESS_API".
>>>>
>>>> [1]:https://lore.kernel.org/lkml/202211301946.pkLE4PDp-lkp@intel.com/
>>>> ---
>>>>    kernel/trace/trace_eprobe.c       | 144 ------------------------------
>>>>    kernel/trace/trace_events_synth.c |   7 +-
>>>>    kernel/trace/trace_kprobe.c       | 102 ---------------------
>>>>    kernel/trace/trace_probe_kernel.h | 143 +++++++++++++++++++++++++++--
>>>>    4 files changed, 141 insertions(+), 255 deletions(-)
>>>>
>>>> diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
>>>> index bdb26eee7a0c..60ced4a7a25d 100644
>>>> --- a/kernel/trace/trace_eprobe.c
>>>> +++ b/kernel/trace/trace_eprobe.c
>>>> @@ -319,64 +319,6 @@ print_eprobe_event(struct trace_iterator *iter, int flags,
>>>>    	return trace_handle_return(s);
>>>>    }
>>>>    
>>>> -static unsigned long get_event_field(struct fetch_insn *code, void *rec)
>>>> -{
>>>> -	struct ftrace_event_field *field = code->data;
>>>> -	unsigned long val;
>>>> -	void *addr;
>>>> -
>>>> -	addr = rec + field->offset;
>>>> -
>>>> -	if (is_string_field(field)) {
>>>> -		switch (field->filter_type) {
>>>> -		case FILTER_DYN_STRING:
>>>> -			val = (unsigned long)(rec + (*(unsigned int *)addr & 0xffff));
>>>> -			break;
>>>> -		case FILTER_RDYN_STRING:
>>>> -			val = (unsigned long)(addr + (*(unsigned int *)addr & 0xffff));
>>>> -			break;
>>>> -		case FILTER_STATIC_STRING:
>>>> -			val = (unsigned long)addr;
>>>> -			break;
>>>> -		case FILTER_PTR_STRING:
>>>> -			val = (unsigned long)(*(char *)addr);
>>>> -			break;
>>>> -		default:
>>>> -			WARN_ON_ONCE(1);
>>>> -			return 0;
>>>> -		}
>>>> -		return val;
>>>> -	}
>>>> -
>>>> -	switch (field->size) {
>>>> -	case 1:
>>>> -		if (field->is_signed)
>>>> -			val = *(char *)addr;
>>>> -		else
>>>> -			val = *(unsigned char *)addr;
>>>> -		break;
>>>> -	case 2:
>>>> -		if (field->is_signed)
>>>> -			val = *(short *)addr;
>>>> -		else
>>>> -			val = *(unsigned short *)addr;
>>>> -		break;
>>>> -	case 4:
>>>> -		if (field->is_signed)
>>>> -			val = *(int *)addr;
>>>> -		else
>>>> -			val = *(unsigned int *)addr;
>>>> -		break;
>>>> -	default:
>>>> -		if (field->is_signed)
>>>> -			val = *(long *)addr;
>>>> -		else
>>>> -			val = *(unsigned long *)addr;
>>>> -		break;
>>>> -	}
>>>> -	return val;
>>>> -}
>>>> -
>>>>    static int get_eprobe_size(struct trace_probe *tp, void *rec)
>>>>    {
>>>>    	struct fetch_insn *code;
>>>> @@ -419,92 +361,6 @@ static int get_eprobe_size(struct trace_probe *tp, void *rec)
>>>>    	return ret;
>>>>    }
>>>>    
>>>> -/* Kprobe specific fetch functions */
>>>> -
>>>> -/* Note that we don't verify it, since the code does not come from user space */
>>>> -static int
>>>> -process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
>>>> -		   void *base)
>>>> -{
>>>> -	unsigned long val;
>>>> -
>>>> - retry:
>>>> -	switch (code->op) {
>>>> -	case FETCH_OP_TP_ARG:
>>>> -		val = get_event_field(code, rec);
>>>> -		break;
>>>> -	case FETCH_OP_IMM:
>>>> -		val = code->immediate;
>>>> -		break;
>>>> -	case FETCH_OP_COMM:
>>>> -		val = (unsigned long)current->comm;
>>>> -		break;
>>>> -	case FETCH_OP_DATA:
>>>> -		val = (unsigned long)code->data;
>>>> -		break;
>>>> -	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
>>>> -		code++;
>>>> -		goto retry;
>>>> -	default:
>>>> -		return -EILSEQ;
>>>> -	}
>>>> -	code++;
>>>> -	return process_fetch_insn_bottom(code, val, dest, base);
>>>> -}
>>>> -NOKPROBE_SYMBOL(process_fetch_insn)
>>>> -
>>>> -/* Return the length of string -- including null terminal byte */
>>>> -static nokprobe_inline int
>>>> -fetch_store_strlen_user(unsigned long addr)
>>>> -{
>>>> -	return kern_fetch_store_strlen_user(addr);
>>>> -}
>>>> -
>>>> -/* Return the length of string -- including null terminal byte */
>>>> -static nokprobe_inline int
>>>> -fetch_store_strlen(unsigned long addr)
>>>> -{
>>>> -	return kern_fetch_store_strlen(addr);
>>>> -}
>>>> -
>>>> -/*
>>>> - * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf
>>>> - * with max length and relative data location.
>>>> - */
>>>> -static nokprobe_inline int
>>>> -fetch_store_string_user(unsigned long addr, void *dest, void *base)
>>>> -{
>>>> -	return kern_fetch_store_string_user(addr, dest, base);
>>>> -}
>>>> -
>>>> -/*
>>>> - * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max
>>>> - * length and relative data location.
>>>> - */
>>>> -static nokprobe_inline int
>>>> -fetch_store_string(unsigned long addr, void *dest, void *base)
>>>> -{
>>>> -	return kern_fetch_store_string(addr, dest, base);
>>>> -}
>>>> -
>>>> -static nokprobe_inline int
>>>> -probe_mem_read_user(void *dest, void *src, size_t size)
>>>> -{
>>>> -	const void __user *uaddr =  (__force const void __user *)src;
>>>> -
>>>> -	return copy_from_user_nofault(dest, uaddr, size);
>>>> -}
>>>> -
>>>> -static nokprobe_inline int
>>>> -probe_mem_read(void *dest, void *src, size_t size)
>>>> -{
>>>> -#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>>>> -	if ((unsigned long)src < TASK_SIZE)
>>>> -		return probe_mem_read_user(dest, src, size);
>>>> -#endif
>>>> -	return copy_from_kernel_nofault(dest, src, size);
>>>> -}
>>>> -
>>>>    /* eprobe handler */
>>>>    static inline void
>>>>    __eprobe_trace_func(struct eprobe_data *edata, void *rec)
>>>> diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
>>>> index e310052dc83c..7460f18ba973 100644
>>>> --- a/kernel/trace/trace_events_synth.c
>>>> +++ b/kernel/trace/trace_events_synth.c
>>>> @@ -18,6 +18,7 @@
>>>>    #include <linux/trace_events.h>
>>>>    #include <trace/events/mmflags.h>
>>>>    #include "trace_probe.h"
>>>> +#include "trace_probe_tmpl.h"
>>>>    #include "trace_probe_kernel.h"
>>>>    
>>>>    #include "trace_synth.h"
>>>> @@ -420,12 +421,12 @@ static unsigned int trace_string(struct synth_trace_event *entry,
>>>>    		data_offset += event->n_u64 * sizeof(u64);
>>>>    		data_offset += data_size;
>>>>    
>>>> -		len = kern_fetch_store_strlen((unsigned long)str_val);
>>>> +		len = fetch_store_strlen((unsigned long)str_val);
>>>>    
>>>>    		data_offset |= len << 16;
>>>>    		*(u32 *)&entry->fields[*n_u64] = data_offset;
>>>>    
>>>> -		ret = kern_fetch_store_string((unsigned long)str_val, &entry->fields[*n_u64], entry);
>>>> +		ret = fetch_store_string((unsigned long)str_val, &entry->fields[*n_u64], entry);
>>>>    
>>>>    		(*n_u64)++;
>>>>    	} else {
>>>> @@ -473,7 +474,7 @@ static notrace void trace_event_raw_event_synth(void *__data,
>>>>    		val_idx = var_ref_idx[field_pos];
>>>>    		str_val = (char *)(long)var_ref_vals[val_idx];
>>>>    
>>>> -		len = kern_fetch_store_strlen((unsigned long)str_val);
>>>> +		len = fetch_store_strlen((unsigned long)str_val);
>>>>    
>>>>    		fields_size += len;
>>>>    	}
>>>> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
>>>> index a4ffa864dbb7..c2e0b741ae82 100644
>>>> --- a/kernel/trace/trace_kprobe.c
>>>> +++ b/kernel/trace/trace_kprobe.c
>>>> @@ -1218,108 +1218,6 @@ static const struct file_operations kprobe_profile_ops = {
>>>>    	.release        = seq_release,
>>>>    };
>>>>    
>>>> -/* Kprobe specific fetch functions */
>>>> -
>>>> -/* Return the length of string -- including null terminal byte */
>>>> -static nokprobe_inline int
>>>> -fetch_store_strlen_user(unsigned long addr)
>>>> -{
>>>> -	return kern_fetch_store_strlen_user(addr);
>>>> -}
>>>> -
>>>> -/* Return the length of string -- including null terminal byte */
>>>> -static nokprobe_inline int
>>>> -fetch_store_strlen(unsigned long addr)
>>>> -{
>>>> -	return kern_fetch_store_strlen(addr);
>>>> -}
>>>> -
>>>> -/*
>>>> - * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf
>>>> - * with max length and relative data location.
>>>> - */
>>>> -static nokprobe_inline int
>>>> -fetch_store_string_user(unsigned long addr, void *dest, void *base)
>>>> -{
>>>> -	return kern_fetch_store_string_user(addr, dest, base);
>>>> -}
>>>> -
>>>> -/*
>>>> - * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max
>>>> - * length and relative data location.
>>>> - */
>>>> -static nokprobe_inline int
>>>> -fetch_store_string(unsigned long addr, void *dest, void *base)
>>>> -{
>>>> -	return kern_fetch_store_string(addr, dest, base);
>>>> -}
>>>> -
>>>> -static nokprobe_inline int
>>>> -probe_mem_read_user(void *dest, void *src, size_t size)
>>>> -{
>>>> -	const void __user *uaddr =  (__force const void __user *)src;
>>>> -
>>>> -	return copy_from_user_nofault(dest, uaddr, size);
>>>> -}
>>>> -
>>>> -static nokprobe_inline int
>>>> -probe_mem_read(void *dest, void *src, size_t size)
>>>> -{
>>>> -#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>>>> -	if ((unsigned long)src < TASK_SIZE)
>>>> -		return probe_mem_read_user(dest, src, size);
>>>> -#endif
>>>> -	return copy_from_kernel_nofault(dest, src, size);
>>>> -}
>>>> -
>>>> -/* Note that we don't verify it, since the code does not come from user space */
>>>> -static int
>>>> -process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
>>>> -		   void *base)
>>>> -{
>>>> -	struct pt_regs *regs = rec;
>>>> -	unsigned long val;
>>>> -
>>>> -retry:
>>>> -	/* 1st stage: get value from context */
>>>> -	switch (code->op) {
>>>> -	case FETCH_OP_REG:
>>>> -		val = regs_get_register(regs, code->param);
>>>> -		break;
>>>> -	case FETCH_OP_STACK:
>>>> -		val = regs_get_kernel_stack_nth(regs, code->param);
>>>> -		break;
>>>> -	case FETCH_OP_STACKP:
>>>> -		val = kernel_stack_pointer(regs);
>>>> -		break;
>>>> -	case FETCH_OP_RETVAL:
>>>> -		val = regs_return_value(regs);
>>>> -		break;
>>>> -	case FETCH_OP_IMM:
>>>> -		val = code->immediate;
>>>> -		break;
>>>> -	case FETCH_OP_COMM:
>>>> -		val = (unsigned long)current->comm;
>>>> -		break;
>>>> -	case FETCH_OP_DATA:
>>>> -		val = (unsigned long)code->data;
>>>> -		break;
>>>> -#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
>>>> -	case FETCH_OP_ARG:
>>>> -		val = regs_get_kernel_argument(regs, code->param);
>>>> -		break;
>>>> -#endif
>>>> -	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
>>>> -		code++;
>>>> -		goto retry;
>>>> -	default:
>>>> -		return -EILSEQ;
>>>> -	}
>>>> -	code++;
>>>> -
>>>> -	return process_fetch_insn_bottom(code, val, dest, base);
>>>> -}
>>>> -NOKPROBE_SYMBOL(process_fetch_insn)
>>>>    
>>>>    /* Kprobe handler */
>>>>    static nokprobe_inline void
>>>> diff --git a/kernel/trace/trace_probe_kernel.h b/kernel/trace/trace_probe_kernel.h
>>>> index 77dbd9ff9782..39f44513ec4e 100644
>>>> --- a/kernel/trace/trace_probe_kernel.h
>>>> +++ b/kernel/trace/trace_probe_kernel.h
>>>> @@ -12,7 +12,7 @@
>>>>     */
>>>>    /* Return the length of string -- including null terminal byte */
>>>>    static nokprobe_inline int
>>>> -kern_fetch_store_strlen_user(unsigned long addr)
>>>> +fetch_store_strlen_user(unsigned long addr)
>>>>    {
>>>>    	const void __user *uaddr =  (__force const void __user *)addr;
>>>>    	int ret;
>>>> @@ -29,14 +29,14 @@ kern_fetch_store_strlen_user(unsigned long addr)
>>>>    
>>>>    /* Return the length of string -- including null terminal byte */
>>>>    static nokprobe_inline int
>>>> -kern_fetch_store_strlen(unsigned long addr)
>>>> +fetch_store_strlen(unsigned long addr)
>>>>    {
>>>>    	int ret, len = 0;
>>>>    	u8 c;
>>>>    
>>>>    #ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>>>>    	if (addr < TASK_SIZE)
>>>> -		return kern_fetch_store_strlen_user(addr);
>>>> +		return fetch_store_strlen_user(addr);
>>>>    #endif
>>>>    
>>>>    	do {
>>>> @@ -63,7 +63,7 @@ static nokprobe_inline void set_data_loc(int ret, void *dest, void *__dest, void
>>>>     * with max length and relative data location.
>>>>     */
>>>>    static nokprobe_inline int
>>>> -kern_fetch_store_string_user(unsigned long addr, void *dest, void *base)
>>>> +fetch_store_string_user(unsigned long addr, void *dest, void *base)
>>>>    {
>>>>    	const void __user *uaddr =  (__force const void __user *)addr;
>>>>    	int maxlen = get_loc_len(*(u32 *)dest);
>>>> @@ -86,7 +86,7 @@ kern_fetch_store_string_user(unsigned long addr, void *dest, void *base)
>>>>     * length and relative data location.
>>>>     */
>>>>    static nokprobe_inline int
>>>> -kern_fetch_store_string(unsigned long addr, void *dest, void *base)
>>>> +fetch_store_string(unsigned long addr, void *dest, void *base)
>>>>    {
>>>>    	int maxlen = get_loc_len(*(u32 *)dest);
>>>>    	void *__dest;
>>>> @@ -94,7 +94,7 @@ kern_fetch_store_string(unsigned long addr, void *dest, void *base)
>>>>    
>>>>    #ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>>>>    	if ((unsigned long)addr < TASK_SIZE)
>>>> -		return kern_fetch_store_string_user(addr, dest, base);
>>>> +		return fetch_store_string_user(addr, dest, base);
>>>>    #endif
>>>>    
>>>>    	if (unlikely(!maxlen))
>>>> @@ -112,4 +112,135 @@ kern_fetch_store_string(unsigned long addr, void *dest, void *base)
>>>>    	return ret;
>>>>    }
>>>>    
>>>> +static nokprobe_inline int
>>>> +probe_mem_read_user(void *dest, void *src, size_t size)
>>>> +{
>>>> +	const void __user *uaddr =  (__force const void __user *)src;
>>>> +
>>>> +	return copy_from_user_nofault(dest, uaddr, size);
>>>> +}
>>>> +
>>>> +static nokprobe_inline int
>>>> +probe_mem_read(void *dest, void *src, size_t size)
>>>> +{
>>>> +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>>>> +	if ((unsigned long)src < TASK_SIZE)
>>>> +		return probe_mem_read_user(dest, src, size);
>>>> +#endif
>>>> +	return copy_from_kernel_nofault(dest, src, size);
>>>> +}
>>>> +
>>>> +static nokprobe_inline unsigned long
>>>> +get_event_field(struct fetch_insn *code, void *rec)
>>>> +{
>>>> +	struct ftrace_event_field *field = code->data;
>>>> +	unsigned long val;
>>>> +	void *addr;
>>>> +
>>>> +	addr = rec + field->offset;
>>>> +
>>>> +	if (is_string_field(field)) {
>>>> +		switch (field->filter_type) {
>>>> +		case FILTER_DYN_STRING:
>>>> +			val = (unsigned long)(rec + (*(unsigned int *)addr & 0xffff));
>>>> +			break;
>>>> +		case FILTER_RDYN_STRING:
>>>> +			val = (unsigned long)(addr + (*(unsigned int *)addr & 0xffff));
>>>> +			break;
>>>> +		case FILTER_STATIC_STRING:
>>>> +			val = (unsigned long)addr;
>>>> +			break;
>>>> +		case FILTER_PTR_STRING:
>>>> +			val = (unsigned long)(*(char *)addr);
>>>> +			break;
>>>> +		default:
>>>> +			WARN_ON_ONCE(1);
>>>> +			return 0;
>>>> +		}
>>>> +		return val;
>>>> +	}
>>>> +
>>>> +	switch (field->size) {
>>>> +	case 1:
>>>> +		if (field->is_signed)
>>>> +			val = *(char *)addr;
>>>> +		else
>>>> +			val = *(unsigned char *)addr;
>>>> +		break;
>>>> +	case 2:
>>>> +		if (field->is_signed)
>>>> +			val = *(short *)addr;
>>>> +		else
>>>> +			val = *(unsigned short *)addr;
>>>> +		break;
>>>> +	case 4:
>>>> +		if (field->is_signed)
>>>> +			val = *(int *)addr;
>>>> +		else
>>>> +			val = *(unsigned int *)addr;
>>>> +		break;
>>>> +	default:
>>>> +		if (field->is_signed)
>>>> +			val = *(long *)addr;
>>>> +		else
>>>> +			val = *(unsigned long *)addr;
>>>> +		break;
>>>> +	}
>>>> +	return val;
>>>> +}
>>>> +
>>>> +/* Note that we don't verify it, since the code does not come from user space */
>>>> +static int
>>>> +process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
>>>> +		   void *base)
>>>> +{
>>>> +	struct pt_regs *regs = rec;
>>>> +	unsigned long val;
>>>> +
>>>> +retry:
>>>> +	/* 1st stage: get value from context */
>>>> +	switch (code->op) {
>>>> +#ifdef CONFIG_HAVE_REGS_AND_STACK_ACCESS_API
>>>> +	case FETCH_OP_REG:
>>>> +		val = regs_get_register(regs, code->param);
>>>> +		break;
>>>> +	case FETCH_OP_STACK:
>>>> +		val = regs_get_kernel_stack_nth(regs, code->param);
>>>> +		break;
>>>> +	case FETCH_OP_STACKP:
>>>> +		val = kernel_stack_pointer(regs);
>>>> +		break;
>>>> +	case FETCH_OP_RETVAL:
>>>> +		val = regs_return_value(regs);
>>>> +		break;
>>>> +#endif
>>>> +	case FETCH_OP_IMM:
>>>> +		val = code->immediate;
>>>> +		break;
>>>> +	case FETCH_OP_COMM:
>>>> +		val = (unsigned long)current->comm;
>>>> +		break;
>>>> +	case FETCH_OP_DATA:
>>>> +		val = (unsigned long)code->data;
>>>> +		break;
>>>> +#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
>>>> +	case FETCH_OP_ARG:
>>>> +		val = regs_get_kernel_argument(regs, code->param);
>>>> +		break;
>>>> +#endif
>>>> +	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
>>>> +		code++;
>>>> +		goto retry;
>>>> +	case FETCH_OP_TP_ARG:
>>>> +		val = get_event_field(code, rec);
>>>> +		break;
>>>> +	default:
>>>> +		return -EILSEQ;
>>>> +	}
>>>> +	code++;
>>>> +
>>>> +	return process_fetch_insn_bottom(code, val, dest, base);
>>>> +}
>>>> +NOKPROBE_SYMBOL(process_fetch_insn)
>>>> +
>>>>    #endif /* __TRACE_PROBE_KERNEL_H_ */
>>>> -- 
>>>> 2.25.1
>>>>
>>>
>>>
> 
>