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Date:   Tue, 3 Jan 2023 19:33:38 +0900
From:   Masami Hiramatsu (Google) <mhiramat@kernel.org>
To:     Song Chen <chensong_2000@189.cn>
Cc:     rostedt@goodmis.org, arnd@arndb.de, linux-kernel@vger.kernel.org,
        linux-trace-kernel@vger.kernel.org, linux-arch@vger.kernel.org
Subject: Re: [PATCH v4 2/2] kernel/trace: Provide default impelentations
 defined in trace_probe_tmpl.h
Message-Id: <20230103193338.e1dc0aa0716b97619ff8d31b@kernel.org>
In-Reply-To: <fa2a0142-9b14-d74b-6fb7-9746cdc00a10@189.cn>
References: <1672211305-31482-1-git-send-email-chensong_2000@189.cn>
        <20221229183027.6f2c75ba0b2924a2bfd0499d@kernel.org>
        <fa2a0142-9b14-d74b-6fb7-9746cdc00a10@189.cn>
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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!

> 
> 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
> >>
> > 
> > 


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>