The probe can dump the registers or memory, but it is not possible
to dump, say, current->pid. This patch adds the pseudo regs table,
currently it has only two methods to get current/smp_processor_id
but it can be trivially extended.
The syntax is '$cpu' and '$current', we overload FETCH_MTD_reg just
to avoid the new fetch method(s).
Test-case: 452 == offsetof(task_struct, pid), 39 == __NR_getpid,
# perf probe 'sys_getpid%return ret=$retval:s32 pid=+452($current):s32'
# perf record -e probe:sys_getpid perl -e 'syscall 39'
# perf --no-pager script | tail -1
perl 586 [001] 753.102549: probe:sys_getpid: \
(ffffffff81052c00 <- ffffffff8134d012) ret=586 pid=586
Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
kernel/trace/trace_probe.c | 61 +++++++++++++++++++++++++++++++++++++++++---
1 files changed, 57 insertions(+), 4 deletions(-)
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 412e959..b066e9d 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -109,13 +109,14 @@ DEFINE_FETCH_##method(u64)
(FETCH_FUNC_NAME(method, string_size) == fn)) \
&& (fn != NULL))
+static unsigned long probe_get_register(struct pt_regs *, unsigned long);
+
/* Data fetch function templates */
#define DEFINE_FETCH_reg(type) \
static __kprobes void FETCH_FUNC_NAME(reg, type)(struct pt_regs *regs, \
void *offset, void *dest) \
{ \
- *(type *)dest = (type)regs_get_register(regs, \
- (unsigned int)((unsigned long)offset)); \
+ *(type *)dest = (type)probe_get_register(regs, (long)offset); \
}
DEFINE_BASIC_FETCH_FUNCS(reg)
/* No string on the register */
@@ -513,6 +514,52 @@ int traceprobe_split_symbol_offset(char *symbol, unsigned
long *offset)
return 0;
}
+static unsigned long pseudo_reg_cpu(void)
+{
+ return (unsigned long)raw_smp_processor_id();
+}
+
+static unsigned long pseudo_reg_current(void)
+{
+ return (unsigned long)current;
+}
+
+static struct {
+ const char *name;
+ unsigned long (*fetch)(void);
+}
+const pseudo_reg_table[] = {
+ {
+ .name = "cpu",
+ .fetch = pseudo_reg_cpu,
+ },
+ {
+ .name = "current",
+ .fetch = pseudo_reg_current,
+ },
+};
+
+#define PSEUDO_REG_OFFSET 4096 /* arbitrary value > MAX_REG_OFFSET */
+
+static unsigned long probe_get_register(struct pt_regs *regs, unsigned long
offset)
+{
+ if (offset < PSEUDO_REG_OFFSET)
+ return regs_get_register(regs, offset);
+
+ return pseudo_reg_table[offset - PSEUDO_REG_OFFSET].fetch();
+}
+
+static int pseudo_reg_query_offset(const char *name)
+{
+ int nr;
+
+ for (nr = 0; nr < ARRAY_SIZE(pseudo_reg_table); ++nr)
+ if (strcmp(pseudo_reg_table[nr].name, name) == 0)
+ return PSEUDO_REG_OFFSET + nr;
+
+ return -EINVAL;
+}
+
#define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long))
static int parse_probe_vars(char *arg, const struct fetch_type *t,
@@ -542,8 +589,14 @@ static int parse_probe_vars(char *arg, const struct
fetch_type *t,
}
} else
ret = -EINVAL;
- } else
- ret = -EINVAL;
+ } else {
+ ret = pseudo_reg_query_offset(arg);
+ if (ret >= 0) {
+ f->fn = t->fetch[FETCH_MTD_reg];
+ f->data = (void *)(unsigned long)ret;
+ ret = 0;
+ }
+ }
return ret;
}
--
1.5.5.1
--
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