Re: [PATCH v4 2/2] kernel/trace: Provide default impelentations defined in trace_probe_tmpl.h

From: Google
Date: Thu Dec 29 2022 - 04:30:40 EST

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In reply to: Song Chen: "[PATCH v4 2/2] kernel/trace: Provide default impelentations defined in trace_probe_tmpl.h"
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On Wed, 28 Dec 2022 15:08:25 +0800
Song Chen <chensong_2000@xxxxxx> 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,

> 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@xxxxxx>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
>
> ---
> 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@xxxxxxxxx/
> ---
> 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@xxxxxxxxxx>

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