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tracing: probeevent: Introduce new argument fetching code
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Replace {k,u}probe event argument fetching framework with switch-case based.
Currently that is implemented with structures, macros and chain of
function-pointers, which is more complicated than necessary and may get a
performance penalty by retpoline.

This simplify that with an array of "fetch_insn" (opcode and oprands), and
make process_fetch_insn() just interprets it. No function pointers are used.

Link: http://lkml.kernel.org/r/152465868340.26224.2551120475197839464.stgit@devbox

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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Masami Hiramatsu authored and Steven Rostedt (VMware) committed Oct 11, 2018
1 parent 7bfbc63 commit 5330592
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Showing 5 changed files with 491 additions and 678 deletions.
291 changes: 131 additions & 160 deletions kernel/trace/trace_kprobe.c
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@

#include "trace_kprobe_selftest.h"
#include "trace_probe.h"
#include "trace_probe_tmpl.h"

#define KPROBE_EVENT_SYSTEM "kprobes"
#define KRETPROBE_MAXACTIVE_MAX 4096
Expand Down Expand Up @@ -120,160 +121,6 @@ static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs);
static int kretprobe_dispatcher(struct kretprobe_instance *ri,
struct pt_regs *regs);

/* Memory fetching by symbol */
struct symbol_cache {
char *symbol;
long offset;
unsigned long addr;
};

unsigned long update_symbol_cache(struct symbol_cache *sc)
{
sc->addr = (unsigned long)kallsyms_lookup_name(sc->symbol);

if (sc->addr)
sc->addr += sc->offset;

return sc->addr;
}

void free_symbol_cache(struct symbol_cache *sc)
{
kfree(sc->symbol);
kfree(sc);
}

struct symbol_cache *alloc_symbol_cache(const char *sym, long offset)
{
struct symbol_cache *sc;

if (!sym || strlen(sym) == 0)
return NULL;

sc = kzalloc(sizeof(struct symbol_cache), GFP_KERNEL);
if (!sc)
return NULL;

sc->symbol = kstrdup(sym, GFP_KERNEL);
if (!sc->symbol) {
kfree(sc);
return NULL;
}
sc->offset = offset;
update_symbol_cache(sc);

return sc;
}

/*
* Kprobes-specific fetch functions
*/
#define DEFINE_FETCH_stack(type) \
static void FETCH_FUNC_NAME(stack, type)(struct pt_regs *regs, \
void *offset, void *dest) \
{ \
*(type *)dest = (type)regs_get_kernel_stack_nth(regs, \
(unsigned int)((unsigned long)offset)); \
} \
NOKPROBE_SYMBOL(FETCH_FUNC_NAME(stack, type));

DEFINE_BASIC_FETCH_FUNCS(stack)
/* No string on the stack entry */
#define fetch_stack_string NULL
#define fetch_stack_string_size NULL

#define DEFINE_FETCH_memory(type) \
static void FETCH_FUNC_NAME(memory, type)(struct pt_regs *regs, \
void *addr, void *dest) \
{ \
type retval; \
if (probe_kernel_address(addr, retval)) \
*(type *)dest = 0; \
else \
*(type *)dest = retval; \
} \
NOKPROBE_SYMBOL(FETCH_FUNC_NAME(memory, type));

DEFINE_BASIC_FETCH_FUNCS(memory)
/*
* Fetch a null-terminated string. Caller MUST set *(u32 *)dest with max
* length and relative data location.
*/
static void FETCH_FUNC_NAME(memory, string)(struct pt_regs *regs,
void *addr, void *dest)
{
int maxlen = get_rloc_len(*(u32 *)dest);
u8 *dst = get_rloc_data(dest);
long ret;

if (!maxlen)
return;

/*
* Try to get string again, since the string can be changed while
* probing.
*/
ret = strncpy_from_unsafe(dst, addr, maxlen);

if (ret < 0) { /* Failed to fetch string */
dst[0] = '\0';
*(u32 *)dest = make_data_rloc(0, get_rloc_offs(*(u32 *)dest));
} else {
*(u32 *)dest = make_data_rloc(ret, get_rloc_offs(*(u32 *)dest));
}
}
NOKPROBE_SYMBOL(FETCH_FUNC_NAME(memory, string));

/* Return the length of string -- including null terminal byte */
static void FETCH_FUNC_NAME(memory, string_size)(struct pt_regs *regs,
void *addr, void *dest)
{
mm_segment_t old_fs;
int ret, len = 0;
u8 c;

old_fs = get_fs();
set_fs(KERNEL_DS);
pagefault_disable();

do {
ret = __copy_from_user_inatomic(&c, (u8 *)addr + len, 1);
len++;
} while (c && ret == 0 && len < MAX_STRING_SIZE);

pagefault_enable();
set_fs(old_fs);

if (ret < 0) /* Failed to check the length */
*(u32 *)dest = 0;
else
*(u32 *)dest = len;
}
NOKPROBE_SYMBOL(FETCH_FUNC_NAME(memory, string_size));

#define DEFINE_FETCH_symbol(type) \
void FETCH_FUNC_NAME(symbol, type)(struct pt_regs *regs, void *data, void *dest)\
{ \
struct symbol_cache *sc = data; \
if (sc->addr) \
fetch_memory_##type(regs, (void *)sc->addr, dest); \
else \
*(type *)dest = 0; \
} \
NOKPROBE_SYMBOL(FETCH_FUNC_NAME(symbol, type));

DEFINE_BASIC_FETCH_FUNCS(symbol)
DEFINE_FETCH_symbol(string)
DEFINE_FETCH_symbol(string_size)

/* kprobes don't support file_offset fetch methods */
#define fetch_file_offset_u8 NULL
#define fetch_file_offset_u16 NULL
#define fetch_file_offset_u32 NULL
#define fetch_file_offset_u64 NULL
#define fetch_file_offset_string NULL
#define fetch_file_offset_string_size NULL

/* Fetch type information table */
static const struct fetch_type kprobes_fetch_type_table[] = {
/* Special types */
Expand Down Expand Up @@ -529,7 +376,7 @@ static bool within_notrace_func(struct trace_kprobe *tk)
/* Internal register function - just handle k*probes and flags */
static int __register_trace_kprobe(struct trace_kprobe *tk)
{
int i, ret;
int ret;

if (trace_probe_is_registered(&tk->tp))
return -EINVAL;
Expand All @@ -540,9 +387,6 @@ static int __register_trace_kprobe(struct trace_kprobe *tk)
return -EINVAL;
}

for (i = 0; i < tk->tp.nr_args; i++)
traceprobe_update_arg(&tk->tp.args[i]);

/* Set/clear disabled flag according to tp->flag */
if (trace_probe_is_enabled(&tk->tp))
tk->rp.kp.flags &= ~KPROBE_FLAG_DISABLED;
Expand Down Expand Up @@ -876,8 +720,8 @@ static int create_trace_kprobe(int argc, char **argv)

/* Parse fetch argument */
ret = traceprobe_parse_probe_arg(arg, &tk->tp.size, parg,
is_return, true,
kprobes_fetch_type_table);
is_return, true,
kprobes_fetch_type_table);
if (ret) {
pr_info("Parse error at argument[%d]. (%d)\n", i, ret);
goto error;
Expand Down Expand Up @@ -1031,6 +875,133 @@ 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 void
fetch_store_strlen(unsigned long addr, void *dest)
{
mm_segment_t old_fs;
int ret, len = 0;
u8 c;

old_fs = get_fs();
set_fs(KERNEL_DS);
pagefault_disable();

do {
ret = __copy_from_user_inatomic(&c, (u8 *)addr + len, 1);
len++;
} while (c && ret == 0 && len < MAX_STRING_SIZE);

pagefault_enable();
set_fs(old_fs);

if (ret < 0) /* Failed to check the length */
*(u32 *)dest = 0;
else
*(u32 *)dest = len;
}

/*
* Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max
* length and relative data location.
*/
static nokprobe_inline void
fetch_store_string(unsigned long addr, void *dest)
{
int maxlen = get_rloc_len(*(u32 *)dest);
u8 *dst = get_rloc_data(dest);
long ret;

if (!maxlen)
return;

/*
* Try to get string again, since the string can be changed while
* probing.
*/
ret = strncpy_from_unsafe(dst, (void *)addr, maxlen);

if (ret < 0) { /* Failed to fetch string */
dst[0] = '\0';
*(u32 *)dest = make_data_rloc(0, get_rloc_offs(*(u32 *)dest));
} else {
*(u32 *)dest = make_data_rloc(ret, get_rloc_offs(*(u32 *)dest));
}
}

/* 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, struct pt_regs *regs, void *dest,
bool pre)
{
unsigned long val;
int ret;

/* 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;
default:
return -EILSEQ;
}
code++;

/* 2nd stage: dereference memory if needed */
while (code->op == FETCH_OP_DEREF) {
ret = probe_kernel_read(&val, (void *)val + code->offset,
sizeof(val));
if (ret)
return ret;
code++;
}

/* 3rd stage: store value to buffer */
switch (code->op) {
case FETCH_OP_ST_RAW:
fetch_store_raw(val, code, dest);
break;
case FETCH_OP_ST_MEM:
probe_kernel_read(dest, (void *)val + code->offset, code->size);
break;
case FETCH_OP_ST_STRING:
if (pre)
fetch_store_strlen(val + code->offset, dest);
else
fetch_store_string(val + code->offset, dest);
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++;
}

return code->op == FETCH_OP_END ? 0 : -EILSEQ;
}
NOKPROBE_SYMBOL(process_fetch_insn)

/* Kprobe handler */
static nokprobe_inline void
__kprobe_trace_func(struct trace_kprobe *tk, struct pt_regs *regs,
Expand Down
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