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Message-Id: <20221122131831.9395fe8db1c0d12147a2369e@kernel.org>
Date: Tue, 22 Nov 2022 13:18:31 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Song Chen <chensong_2000@....cn>
Cc: rostedt@...dmis.org, linux-kernel@...r.kernel.org,
linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] kernel/trace: Introduce new APIs to process probe
arguments
On Tue, 22 Nov 2022 10:05:07 +0800
Song Chen <chensong_2000@....cn> wrote:
> Hi,
>
> 在 2022/11/22 06:16, Masami Hiramatsu (Google) 写道:
> > On Wed, 16 Nov 2022 20:25:07 +0800
> > Song Chen <chensong_2000@....cn> wrote:
> >
> >> Introduce 3 new APIs:
> >> 1. trace_probe_get_data_size: get arguments' data size
> >> 2. trace_probe_store_args: store aruguments into ring buffer
> >> 3. trace_probe_print_args: print arguments into trace file
> >>
> >> Those APIs are going to merge similar implementations respectively
> >> in kprobe/uprobe/eprobe.
> >>
> >> Signed-off-by: Song Chen <chensong_2000@....cn>
> >> ---
> >> kernel/trace/trace_probe.c | 305 ++++++++++++++++++++++++++++++
> >> kernel/trace/trace_probe.h | 5 +
> >> kernel/trace/trace_probe_common.h | 69 +++++++
> >> kernel/trace/trace_probe_user.h | 95 ++++++++++
> >> 4 files changed, 474 insertions(+)
> >> create mode 100644 kernel/trace/trace_probe_common.h
> >> create mode 100644 kernel/trace/trace_probe_user.h
> >>
> >> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> >> index 36dff277de46..303f057bd2f7 100644
> >> --- a/kernel/trace/trace_probe.c
> >> +++ b/kernel/trace/trace_probe.c
> >> @@ -12,6 +12,9 @@
> >> #define pr_fmt(fmt) "trace_probe: " fmt
> >>
> >> #include "trace_probe.h"
> >> +#include "trace_probe_kernel.h"
> >> +#include "trace_probe_user.h"
> >> +#include "trace_probe_common.h"
> >>
> >> #undef C
> >> #define C(a, b) b
> >> @@ -1218,3 +1221,305 @@ int trace_probe_create(const char *raw_command, int (*createfn)(int, const char
> >>
> >> return ret;
> >> }
> >> +
> >> +/* From the 2nd stage, routine is same */
> >> +static nokprobe_inline int
> >> +process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,
> >> + void *dest, void *base, int flags)
> >> +{
> >> + struct fetch_insn *s3 = NULL;
> >> + int total = 0, ret = 0, i = 0;
> >> + u32 loc = 0;
> >> + unsigned long lval = val;
> >> + int is_uprobe = flags & TRACE_EVENT_FL_UPROBE;
> >> +
> >> +stage2:
> >> + /* 2nd stage: dereference memory if needed */
> >> + do {
> >> + if (code->op == FETCH_OP_DEREF) {
> >> + lval = val;
> >> + ret = probe_mem_read(&val, (void *)val + code->offset,
> >> + sizeof(val));
> >> + } else if (code->op == FETCH_OP_UDEREF) {
> >> + lval = val;
> >> + ret = probe_mem_read_user(&val,
> >> + (void *)val + code->offset, sizeof(val));
> >> + } else
> >> + break;
> >> + if (ret)
> >> + return ret;
> >> + code++;
> >> + } while (1);
> >> +
> >> + s3 = code;
> >> +stage3:
> >> + /* 3rd stage: store value to buffer */
> >> + if (unlikely(!dest)) {
> >> + if (code->op == FETCH_OP_ST_STRING) {
> >> + if (is_uprobe)
> >> + ret = user_fetch_store_strlen(val + code->offset);
> >> + else
> >> + ret = kern_fetch_store_strlen(val + code->offset);
> >> + code++;
> >> + goto array;
> >> + } else if (code->op == FETCH_OP_ST_USTRING) {
> >> + if (is_uprobe)
> >> + ret += user_fetch_store_strlen_user(val + code->offset);
> >> + else
> >> + ret += kern_fetch_store_strlen_user(val + code->offset);
> >
> > Also, I would not like to see this "is_uprobe" check in the code. That is useless
> > when running this in the kernel. This is why I did this in trace_probe_tmpl.h as
> > an inlined function.
> >
>
> one of the intention is to merge process_fetch_insn*, that's why
> is_uprobe is introduced here, otherwise, process_fetch_insn* doesn't
> know which kind of probe it's dealing with.
>
> > So, sorting print_args function is OK for me, but the process_fetch_insn* should be
> > kept as inlined. Maybe some common code can be move to the trace_probe_tmpl.h as
> > inlined functions?
> >
>
> if i understand you correctly, you would like to remain
> process_fetch_insn* as the way they are, no change.
Yeah, that's the point. Maybe we can put more things in trace_probe_tmpl.h but
not completely make it a big function.
Thank you,
>
> Maybe i went too far, i will submit a new patchset to restore.
>
> /Song
>
> >
> >> + code++;
> >> + goto array;
> >> + } else
> >> + return -EILSEQ;
> >> + }
> >> +
> >> + switch (code->op) {
> >> + case FETCH_OP_ST_RAW:
> >> + fetch_store_raw(val, code, dest);
> >> + break;
> >> + case FETCH_OP_ST_MEM:
> >> + probe_mem_read(dest, (void *)val + code->offset, code->size);
> >> + break;
> >> + case FETCH_OP_ST_UMEM:
> >> + probe_mem_read_user(dest, (void *)val + code->offset, code->size);
> >> + break;
> >> + case FETCH_OP_ST_STRING:
> >> + loc = *(u32 *)dest;
> >> + if (is_uprobe)
> >> + ret = user_fetch_store_string(val + code->offset, dest, base);
> >> + else
> >> + ret = kern_fetch_store_string(val + code->offset, dest, base);
> >> + break;
> >> + case FETCH_OP_ST_USTRING:
> >> + loc = *(u32 *)dest;
> >> + if (is_uprobe)
> >> + ret = user_fetch_store_string_user(val + code->offset, dest, base);
> >> + else
> >> + ret = kern_fetch_store_string_user(val + code->offset, dest, base);
> >> + break;
> >> + default:
> >> + return -EILSEQ;
> >> + }
> >> + code++;
> >> +
> >> + /* 4th stage: modify stored value if needed */
> >> + if (code->op == FETCH_OP_MOD_BF) {
> >> + fetch_apply_bitfield(code, dest);
> >> + code++;
> >> + }
> >> +
> >> +array:
> >> + /* the last stage: Loop on array */
> >> + if (code->op == FETCH_OP_LP_ARRAY) {
> >> + total += ret;
> >> + if (++i < code->param) {
> >> + code = s3;
> >> + if (s3->op != FETCH_OP_ST_STRING &&
> >> + s3->op != FETCH_OP_ST_USTRING) {
> >> + dest += s3->size;
> >> + val += s3->size;
> >> + goto stage3;
> >> + }
> >> + code--;
> >> + val = lval + sizeof(char *);
> >> + if (dest) {
> >> + dest += sizeof(u32);
> >> + *(u32 *)dest = update_data_loc(loc, ret);
> >> + }
> >> + goto stage2;
> >> + }
> >> + code++;
> >> + ret = total;
> >> + }
> >> +
> >> + return code->op == FETCH_OP_END ? ret : -EILSEQ;
> >> +}
> >> +
> >> +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;
> >> +}
> >> +
> >> +/* 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, int flags)
> >> +{
> >> + struct pt_regs *regs = rec;
> >> + unsigned long val;
> >> + int is_uprobe = flags & TRACE_EVENT_FL_UPROBE;
> >> +
> >> +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:
> >> + if (is_uprobe)
> >> + val = get_user_stack_nth(regs, code->param);
> >> + else
> >> + val = regs_get_kernel_stack_nth(regs, code->param);
> >> + break;
> >
> > Ditto.
>
> will do.
>
> /Song
>
> >
> >> + case FETCH_OP_STACKP:
> >> + if (is_uprobe)
> >> + val = user_stack_pointer(regs);
> >> + else
> >> + 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;
> >> + 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, flags);
> >> +}
> >> +NOKPROBE_SYMBOL(process_fetch_insn)
> >> +
> >> +/* Sum up total data length for dynamic arrays (strings) */
> >> +int trace_probe_get_data_size(struct trace_probe *tp, struct pt_regs *regs)
> >> +{
> >> + struct probe_arg *arg;
> >> + int i, len, ret = 0;
> >> + struct trace_event_call *call = trace_probe_event_call(tp);
> >> +
> >> + for (i = 0; i < tp->nr_args; i++) {
> >> + arg = tp->args + i;
> >> + if (unlikely(arg->dynamic)) {
> >> + len = process_fetch_insn(arg->code, regs, NULL, NULL, call->flags);
> >> + if (len > 0)
> >> + ret += len;
> >> + }
> >> + }
> >> +
> >> + return ret;
> >> +}
> >> +
> >> +void trace_probe_store_args(void *data, struct trace_probe *tp, void *rec,
> >> + int header_size, int maxlen)
> >> +{
> >> + struct probe_arg *arg;
> >> + void *base = data - header_size;
> >> + void *dyndata = data + tp->size;
> >> + u32 *dl; /* Data location */
> >> + int ret, i;
> >> + struct trace_event_call *call = trace_probe_event_call(tp);
> >> +
> >> + for (i = 0; i < tp->nr_args; i++) {
> >> + arg = tp->args + i;
> >> + dl = data + arg->offset;
> >> + /* Point the dynamic data area if needed */
> >> + if (unlikely(arg->dynamic))
> >> + *dl = make_data_loc(maxlen, dyndata - base);
> >> + ret = process_fetch_insn(arg->code, rec, dl, base, call->flags);
> >> + if (unlikely(ret < 0 && arg->dynamic)) {
> >> + *dl = make_data_loc(0, dyndata - base);
> >> + } else {
> >> + dyndata += ret;
> >> + maxlen -= ret;
> >> + }
> >> + }
> >> +}
> >> +
> >> +int trace_probe_print_args(struct trace_seq *s, struct probe_arg *args, int nr_args,
> >> + u8 *data, void *field)
> >> +{
> >> + void *p;
> >> + int i, j;
> >> +
> >> + for (i = 0; i < nr_args; i++) {
> >> + struct probe_arg *a = args + i;
> >> +
> >> + trace_seq_printf(s, " %s=", a->name);
> >> + if (likely(!a->count)) {
> >> + if (!a->type->print(s, data + a->offset, field))
> >> + return -ENOMEM;
> >> + continue;
> >> + }
> >> + trace_seq_putc(s, '{');
> >> + p = data + a->offset;
> >> + for (j = 0; j < a->count; j++) {
> >> + if (!a->type->print(s, p, field))
> >> + return -ENOMEM;
> >> + trace_seq_putc(s, j == a->count - 1 ? '}' : ',');
> >> + p += a->type->size;
> >> + }
> >> + }
> >> + return 0;
> >> +}
> >> diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
> >> index de38f1c03776..4f044047b748 100644
> >> --- a/kernel/trace/trace_probe.h
> >> +++ b/kernel/trace/trace_probe.h
> >> @@ -343,6 +343,11 @@ int trace_probe_compare_arg_type(struct trace_probe *a, struct trace_probe *b);
> >> bool trace_probe_match_command_args(struct trace_probe *tp,
> >> int argc, const char **argv);
> >> int trace_probe_create(const char *raw_command, int (*createfn)(int, const char **));
> >> +int trace_probe_get_data_size(struct trace_probe *tp, struct pt_regs *regs);
> >> +void trace_probe_store_args(void *data, struct trace_probe *tp, void *rec,
> >> + int header_size, int maxlen);
> >> +int trace_probe_print_args(struct trace_seq *s, struct probe_arg *args, int nr_args,
> >> + u8 *data, void *field);
> >>
> >> #define trace_probe_for_each_link(pos, tp) \
> >> list_for_each_entry(pos, &(tp)->event->files, list)
> >> diff --git a/kernel/trace/trace_probe_common.h b/kernel/trace/trace_probe_common.h
> >> new file mode 100644
> >> index 000000000000..b8d77447fe0c
> >> --- /dev/null
> >> +++ b/kernel/trace/trace_probe_common.h
> >
> > Please do not add an internal header file only just for 1 file.
>
> Will remove.
>
> /Song
>
> >
> >> @@ -0,0 +1,69 @@
> >> +/* SPDX-License-Identifier: GPL-2.0 */
> >> +#ifndef __TRACE_PROBE_COMMON_H_
> >> +#define __TRACE_PROBE_COMMON_H_
> >> +
> >> +#define FAULT_STRING "(fault)"
> >> +
> >> +static nokprobe_inline void
> >> +fetch_store_raw(unsigned long val, struct fetch_insn *code, void *buf)
> >> +{
> >> + switch (code->size) {
> >> + case 1:
> >> + *(u8 *)buf = (u8)val;
> >> + break;
> >> + case 2:
> >> + *(u16 *)buf = (u16)val;
> >> + break;
> >> + case 4:
> >> + *(u32 *)buf = (u32)val;
> >> + break;
> >> + case 8:
> >> + //TBD: 32bit signed
> >> + *(u64 *)buf = (u64)val;
> >> + break;
> >> + default:
> >> + *(unsigned long *)buf = val;
> >> + }
> >> +}
> >> +
> >> +static nokprobe_inline void
> >> +fetch_apply_bitfield(struct fetch_insn *code, void *buf)
> >> +{
> >> + switch (code->basesize) {
> >> + case 1:
> >> + *(u8 *)buf <<= code->lshift;
> >> + *(u8 *)buf >>= code->rshift;
> >> + break;
> >> + case 2:
> >> + *(u16 *)buf <<= code->lshift;
> >> + *(u16 *)buf >>= code->rshift;
> >> + break;
> >> + case 4:
> >> + *(u32 *)buf <<= code->lshift;
> >> + *(u32 *)buf >>= code->rshift;
> >> + break;
> >> + case 8:
> >> + *(u64 *)buf <<= code->lshift;
> >> + *(u64 *)buf >>= code->rshift;
> >> + break;
> >> + }
> >> +}
> >> +
> >> +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);
> >> +}
> >> +#endif /* __TRACE_PROBE_COMMON_H_ */
> >> diff --git a/kernel/trace/trace_probe_user.h b/kernel/trace/trace_probe_user.h
> >> new file mode 100644
> >> index 000000000000..2104ccb44d56
> >> --- /dev/null
> >> +++ b/kernel/trace/trace_probe_user.h
> >
> > Ditto.
> >
> > Thank you,
>
> Ditto, thanks.
>
> /Song
>
> >
> >> @@ -0,0 +1,95 @@
> >> +/* SPDX-License-Identifier: GPL-2.0 */
> >> +#ifndef __TRACE_PROBE_USER_H_
> >> +#define __TRACE_PROBE_USER_H_
> >> +
> >> +#define FAULT_STRING "(fault)"
> >> +
> >> +/*
> >> + * Fetch a null-terminated string. Caller MUST set *(u32 *)dest with max
> >> + * length and relative data location.
> >> + */
> >> +static nokprobe_inline int
> >> +user_fetch_store_string(unsigned long addr, void *dest, void *base)
> >> +{
> >> + long ret;
> >> + u32 loc = *(u32 *)dest;
> >> + int maxlen = get_loc_len(loc);
> >> + u8 *dst = get_loc_data(dest, base);
> >> + void __user *src = (void __force __user *) addr;
> >> +
> >> + if (unlikely(!maxlen))
> >> + return -ENOMEM;
> >> +
> >> + if (addr == FETCH_TOKEN_COMM)
> >> + ret = strlcpy(dst, current->comm, maxlen);
> >> + else
> >> + ret = strncpy_from_user(dst, src, maxlen);
> >> + if (ret >= 0) {
> >> + if (ret == maxlen)
> >> + dst[ret - 1] = '\0';
> >> + else
> >> + /*
> >> + * Include the terminating null byte. In this case it
> >> + * was copied by strncpy_from_user but not accounted
> >> + * for in ret.
> >> + */
> >> + ret++;
> >> + *(u32 *)dest = make_data_loc(ret, (void *)dst - base);
> >> + }
> >> +
> >> + return ret;
> >> +}
> >> +
> >> +static nokprobe_inline int
> >> +user_fetch_store_string_user(unsigned long addr, void *dest, void *base)
> >> +{
> >> + return user_fetch_store_string(addr, dest, base);
> >> +}
> >> +
> >> +/* Return the length of string -- including null terminal byte */
> >> +static nokprobe_inline int
> >> +user_fetch_store_strlen(unsigned long addr)
> >> +{
> >> + int len;
> >> + void __user *vaddr = (void __force __user *) addr;
> >> +
> >> + if (addr == FETCH_TOKEN_COMM)
> >> + len = strlen(current->comm) + 1;
> >> + else
> >> + len = strnlen_user(vaddr, MAX_STRING_SIZE);
> >> +
> >> + return (len > MAX_STRING_SIZE) ? 0 : len;
> >> +}
> >> +
> >> +static nokprobe_inline int
> >> +user_fetch_store_strlen_user(unsigned long addr)
> >> +{
> >> + return user_fetch_store_strlen(addr);
> >> +}
> >> +
> >> +#ifdef CONFIG_STACK_GROWSUP
> >> +static unsigned long adjust_stack_addr(unsigned long addr, unsigned int n)
> >> +{
> >> + return addr - (n * sizeof(long));
> >> +}
> >> +#else
> >> +static unsigned long adjust_stack_addr(unsigned long addr, unsigned int n)
> >> +{
> >> + return addr + (n * sizeof(long));
> >> +}
> >> +#endif
> >> +
> >> +static unsigned long get_user_stack_nth(struct pt_regs *regs, unsigned int n)
> >> +{
> >> + unsigned long ret;
> >> + unsigned long addr = user_stack_pointer(regs);
> >> +
> >> + addr = adjust_stack_addr(addr, n);
> >> +
> >> + if (copy_from_user(&ret, (void __force __user *) addr, sizeof(ret)))
> >> + return 0;
> >> +
> >> + return ret;
> >> +}
> >> +
> >> +#endif /* __TRACE_PROBE_USER_H_ */
> >> --
> >> 2.25.1
> >>
> >
> > Thanks,
> >
--
Masami Hiramatsu (Google) <mhiramat@...nel.org>
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