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tracing/probes: support '%pD' type for print struct file's name

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As like '%pd' type, this patch supports print type '%pD' for print file's
name. For example "name=$arg1:%pD" casts the `$arg1` as (struct file*),
dereferences the "file.f_path.dentry.d_name.name" field and stores it to
"name" argument as a kernel string.
Here is an example:
[tracing]# echo 'p:testprobe vfs_read name=$arg1:%pD' > kprobe_event
[tracing]# echo 1 > events/kprobes/testprobe/enable
[tracing]# grep -q "1" events/kprobes/testprobe/enable
[tracing]# echo 0 > events/kprobes/testprobe/enable
[tracing]# grep "vfs_read" trace | grep "enable"
            grep-15108   [003] .....  5228.328609: testprobe: (vfs_read+0x4/0xbb0) name="enable"

Note that this expects the given argument (e.g. $arg1) is an address of struct
file. User must ensure it.

Link: https://lore.kernel.org/all/20240322064308.284457-3-yebin10@huawei.com/
[Masami: replaced "previous patch" with '%pd' type]

Signed-off-by: Ye Bin <yebin10@huawei.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
This commit is contained in:
Ye Bin
2024-03-22 14:43:05 +08:00
committed by Masami Hiramatsu (Google)
parent d9b15224dd
commit 20fe4d07bd
2 changed files with 35 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
kernel/trace/trace.c
View File

@@ -5540,7 +5540,7 @@ static const char readme_msg[] =
"\t kernel return probes support: $retval, $arg<N>, $comm\n"
"\t type: s8/16/32/64, u8/16/32/64, x8/16/32/64, char, string, symbol,\n"
"\t b<bit-width>@<bit-offset>/<container-size>, ustring,\n"
"\t symstr, %pd, <type>\\[<array-size>\\]\n"
"\t symstr, %pd/%pD, <type>\\[<array-size>\\]\n"
#ifdef CONFIG_HIST_TRIGGERS
"\t field: <stype> <name>;\n"
"\t stype: u8/u16/u32/u64, s8/s16/s32/s64, pid_t,\n"

55
kernel/trace/trace_probe.c
View File

@@ -12,6 +12,7 @@
#define pr_fmt(fmt) "trace_probe: " fmt
#include <linux/bpf.h>
#include <linux/fs.h>
#include "trace_btf.h"
#include "trace_probe.h"
@@ -1751,35 +1752,47 @@ int traceprobe_expand_dentry_args(int argc, const char *argv[], char **buf)
used = 0;
for (i = 0; i < argc; i++) {
if (glob_match("*:%pd", argv[i])) {
char *tmp;
char *equal;
char *tmp;
char *equal;
size_t arg_len;
if (!tmpbuf) {
tmpbuf = kmalloc(bufsize, GFP_KERNEL);
if (!tmpbuf)
return -ENOMEM;
}
if (!glob_match("*:%p[dD]", argv[i]))
continue;
tmp = kstrdup(argv[i], GFP_KERNEL);
if (!tmp)
goto nomem;
if (!tmpbuf) {
tmpbuf = kmalloc(bufsize, GFP_KERNEL);
if (!tmpbuf)
return -ENOMEM;
}
equal = strchr(tmp, '=');
if (equal)
*equal = '\0';
tmp[strlen(argv[i]) - 4] = '\0';
tmp = kstrdup(argv[i], GFP_KERNEL);
if (!tmp)
goto nomem;
equal = strchr(tmp, '=');
if (equal)
*equal = '\0';
arg_len = strlen(argv[i]);
tmp[arg_len - 4] = '\0';
if (argv[i][arg_len - 1] == 'd')
ret = snprintf(tmpbuf + used, bufsize - used,
"%s%s+0x0(+0x%zx(%s)):string",
equal ? tmp : "", equal ? "=" : "",
offsetof(struct dentry, d_name.name),
equal ? equal + 1 : tmp);
kfree(tmp);
if (ret >= bufsize - used)
goto nomem;
argv[i] = tmpbuf + used;
used += ret + 1;
}
else
ret = snprintf(tmpbuf + used, bufsize - used,
"%s%s+0x0(+0x%zx(+0x%zx(%s))):string",
equal ? tmp : "", equal ? "=" : "",
offsetof(struct dentry, d_name.name),
offsetof(struct file, f_path.dentry),
equal ? equal + 1 : tmp);
kfree(tmp);
if (ret >= bufsize - used)
goto nomem;
argv[i] = tmpbuf + used;
used += ret + 1;
}
*buf = tmpbuf;