[PATCH 1/3] tracing/probes: support '%pd' type for print struct dentry's name

[Ye Bin]

Similar to '%pd' for printk, use 'pd' for print struct dentry's name.

Signed-off-by: Ye Bin <yebi...@huawei.com>
---
 kernel/trace/trace_probe.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 4dc74d73fc1d..460f98b85b1c 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -11,6 +11,7 @@
  */
 #define pr_fmt(fmt)    "trace_probe: " fmt
 
+#include <linux/dcache.h>
 #include <linux/bpf.h>
 #include "trace_btf.h"
 
@@ -86,6 +87,8 @@ static const struct fetch_type probe_fetch_types[] = {
                            "__data_loc char[]"),
        __ASSIGN_FETCH_TYPE("symstr", string, string, sizeof(u32), 1, 1,
                            "__data_loc char[]"),
+       __ASSIGN_FETCH_TYPE("pd", string, string, sizeof(u32), 1, 1,
+                           "__data_loc char[]"),
        /* Basic types */
        ASSIGN_FETCH_TYPE(u8,  u8,  0),
        ASSIGN_FETCH_TYPE(u16, u16, 0),
@@ -1090,6 +1093,25 @@ static int __parse_bitfield_probe_arg(const char *bf,
        return (BYTES_TO_BITS(t->size) < (bw + bo)) ? -EINVAL : 0;
 }
 
+static char* traceprobe_expand_dentry(const char *argv)
+{
+       #define DENTRY_EXPAND_LEN 7  /* +0xXX() */
+       char *new_argv;
+       int len = strlen(argv) + 1 + DENTRY_EXPAND_LEN;
+
+       new_argv = kmalloc(len, GFP_KERNEL);
+       if (!new_argv)
+               return NULL;
+
+       if (snprintf(new_argv, len, "+0x%lx(%s)",
+                    offsetof(struct dentry, d_name.name), argv) >= len) {
+               kfree(new_argv);
+               return NULL;
+       }
+
+       return new_argv;
+}
+
 /* String length checking wrapper */
 static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size,
                                           struct probe_arg *parg,
@@ -1099,6 +1121,7 @@ static int traceprobe_parse_probe_arg_body(const char 
*argv, ssize_t *size,
        char *t, *t2, *t3;
        int ret, len;
        char *arg;
+       char *org_arg = NULL;
 
        arg = kstrdup(argv, GFP_KERNEL);
        if (!arg)
@@ -1182,6 +1205,16 @@ static int traceprobe_parse_probe_arg_body(const char 
*argv, ssize_t *size,
                         parg->count);
        }
 
+       if (!strcmp("pd", parg->type->name)) {
+               char *temp;
+
+               temp = traceprobe_expand_dentry(arg);
+               if (!temp)
+                       goto out;
+               org_arg = arg;
+               arg = temp;
+       }
+
        code = tmp = kcalloc(FETCH_INSN_MAX, sizeof(*code), GFP_KERNEL);
        if (!code)
                goto out;
@@ -1243,6 +1276,10 @@ static int traceprobe_parse_probe_arg_body(const char 
*argv, ssize_t *size,
                                goto fail;
                        }
                }
+
+               if (!strcmp(parg->type->name, "pd"))
+                       code++;
+
                /* If op == DEREF, replace it with STRING */
                if (!strcmp(parg->type->name, "ustring") ||
                    code->op == FETCH_OP_UDEREF)
@@ -1321,6 +1358,7 @@ static int traceprobe_parse_probe_arg_body(const char 
*argv, ssize_t *size,
        kfree(tmp);
 out:
        kfree(arg);
+       kfree(org_arg);
 
        return ret;
 }
-- 
2.31.1