From: Alan Maguire <alan.maguire@oracle.com>
To: ast@kernel.org, daniel@iogearbox.net, bpf@vger.kernel.org
Cc: joe@perches.com, linux@rasmusvillemoes.dk,
arnaldo.melo@gmail.com, yhs@fb.com, kafai@fb.com,
songliubraving@fb.com, andriin@fb.com, john.fastabend@gmail.com,
kpsingh@chromium.org, linux-kernel@vger.kernel.org,
netdev@vger.kernel.org, Alan Maguire <alan.maguire@oracle.com>
Subject: [PATCH v2 bpf-next 6/7] bpf: add support for %pT format specifier for bpf_trace_printk() helper
Date: Tue, 12 May 2020 06:56:44 +0100 [thread overview]
Message-ID: <1589263005-7887-7-git-send-email-alan.maguire@oracle.com> (raw)
In-Reply-To: <1589263005-7887-1-git-send-email-alan.maguire@oracle.com>
Allow %pT[cNx0] format specifier for BTF-based display of data associated
with pointer.
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
---
include/uapi/linux/bpf.h | 27 ++++++++++++++++++++++-----
kernel/trace/bpf_trace.c | 21 ++++++++++++++++++---
tools/include/uapi/linux/bpf.h | 27 ++++++++++++++++++++++-----
3 files changed, 62 insertions(+), 13 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 9d1932e..ab3c86c 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -695,7 +695,12 @@ struct bpf_stack_build_id {
* to file *\/sys/kernel/debug/tracing/trace* from DebugFS, if
* available. It can take up to three additional **u64**
* arguments (as an eBPF helpers, the total number of arguments is
- * limited to five).
+ * limited to five), and also supports %pT (BTF-based type
+ * printing), as long as BPF_READ lockdown is not active.
+ * "%pT" takes a "struct __btf_ptr *" as an argument; it
+ * consists of a pointer value and specified BTF type string or id
+ * used to select the type for display. For more details, see
+ * Documentation/core-api/printk-formats.rst.
*
* Each time the helper is called, it appends a line to the trace.
* Lines are discarded while *\/sys/kernel/debug/tracing/trace* is
@@ -731,10 +736,10 @@ struct bpf_stack_build_id {
* The conversion specifiers supported by *fmt* are similar, but
* more limited than for printk(). They are **%d**, **%i**,
* **%u**, **%x**, **%ld**, **%li**, **%lu**, **%lx**, **%lld**,
- * **%lli**, **%llu**, **%llx**, **%p**, **%s**. No modifier (size
- * of field, padding with zeroes, etc.) is available, and the
- * helper will return **-EINVAL** (but print nothing) if it
- * encounters an unknown specifier.
+ * **%lli**, **%llu**, **%llx**, **%p**, **%pT[cNx0], **%s**.
+ * Only %pT supports modifiers, and the helper will return
+ * **-EINVAL** (but print nothing) if it encouters an unknown
+ * specifier.
*
* Also, note that **bpf_trace_printk**\ () is slow, and should
* only be used for debugging purposes. For this reason, a notice
@@ -4058,4 +4063,16 @@ struct bpf_pidns_info {
__u32 pid;
__u32 tgid;
};
+
+/*
+ * struct __btf_ptr is used for %pT (typed pointer) display; the
+ * additional type string/BTF id are used to render the pointer
+ * data as the appropriate type.
+ */
+struct __btf_ptr {
+ void *ptr;
+ const char *type;
+ __u32 id;
+};
+
#endif /* _UAPI__LINUX_BPF_H__ */
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index d961428..c032c58 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -321,9 +321,12 @@ static const struct bpf_func_proto *bpf_get_probe_write_proto(void)
return &bpf_probe_write_user_proto;
}
+#define isbtffmt(c) \
+ (c == 'T' || c == 'c' || c == 'N' || c == 'x' || c == '0')
+
/*
* Only limited trace_printk() conversion specifiers allowed:
- * %d %i %u %x %ld %li %lu %lx %lld %lli %llu %llx %p %s
+ * %d %i %u %x %ld %li %lu %lx %lld %lli %llu %llx %p %pT %s
*/
BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,
u64, arg2, u64, arg3)
@@ -361,8 +364,20 @@ static const struct bpf_func_proto *bpf_get_probe_write_proto(void)
i++;
} else if (fmt[i] == 'p' || fmt[i] == 's') {
mod[fmt_cnt]++;
- /* disallow any further format extensions */
- if (fmt[i + 1] != 0 &&
+ /*
+ * allow BTF type-based printing, and disallow any
+ * further format extensions.
+ */
+ if (fmt[i] == 'p' && fmt[i + 1] == 'T') {
+ int ret;
+
+ ret = security_locked_down(LOCKDOWN_BPF_READ);
+ if (unlikely(ret < 0))
+ return ret;
+ i++;
+ while (isbtffmt(fmt[i]))
+ i++;
+ } else if (fmt[i + 1] != 0 &&
!isspace(fmt[i + 1]) &&
!ispunct(fmt[i + 1]))
return -EINVAL;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 9d1932e..ab3c86c 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -695,7 +695,12 @@ struct bpf_stack_build_id {
* to file *\/sys/kernel/debug/tracing/trace* from DebugFS, if
* available. It can take up to three additional **u64**
* arguments (as an eBPF helpers, the total number of arguments is
- * limited to five).
+ * limited to five), and also supports %pT (BTF-based type
+ * printing), as long as BPF_READ lockdown is not active.
+ * "%pT" takes a "struct __btf_ptr *" as an argument; it
+ * consists of a pointer value and specified BTF type string or id
+ * used to select the type for display. For more details, see
+ * Documentation/core-api/printk-formats.rst.
*
* Each time the helper is called, it appends a line to the trace.
* Lines are discarded while *\/sys/kernel/debug/tracing/trace* is
@@ -731,10 +736,10 @@ struct bpf_stack_build_id {
* The conversion specifiers supported by *fmt* are similar, but
* more limited than for printk(). They are **%d**, **%i**,
* **%u**, **%x**, **%ld**, **%li**, **%lu**, **%lx**, **%lld**,
- * **%lli**, **%llu**, **%llx**, **%p**, **%s**. No modifier (size
- * of field, padding with zeroes, etc.) is available, and the
- * helper will return **-EINVAL** (but print nothing) if it
- * encounters an unknown specifier.
+ * **%lli**, **%llu**, **%llx**, **%p**, **%pT[cNx0], **%s**.
+ * Only %pT supports modifiers, and the helper will return
+ * **-EINVAL** (but print nothing) if it encouters an unknown
+ * specifier.
*
* Also, note that **bpf_trace_printk**\ () is slow, and should
* only be used for debugging purposes. For this reason, a notice
@@ -4058,4 +4063,16 @@ struct bpf_pidns_info {
__u32 pid;
__u32 tgid;
};
+
+/*
+ * struct __btf_ptr is used for %pT (typed pointer) display; the
+ * additional type string/BTF id are used to render the pointer
+ * data as the appropriate type.
+ */
+struct __btf_ptr {
+ void *ptr;
+ const char *type;
+ __u32 id;
+};
+
#endif /* _UAPI__LINUX_BPF_H__ */
--
1.8.3.1
next prev parent reply other threads:[~2020-05-12 5:57 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-12 5:56 [PATCH v2 bpf-next 0/7] bpf, printk: add BTF-based type printing Alan Maguire
2020-05-12 5:56 ` [PATCH v2 bpf-next 1/7] bpf: provide function to get vmlinux BTF information Alan Maguire
2020-05-12 5:56 ` [PATCH v2 bpf-next 2/7] bpf: move to generic BTF show support, apply it to seq files/strings Alan Maguire
2020-05-13 23:04 ` Yonghong Song
2020-05-18 9:46 ` Alan Maguire
2020-05-19 6:21 ` Yonghong Song
2020-05-12 5:56 ` [PATCH v2 bpf-next 3/7] checkpatch: add new BTF pointer format specifier Alan Maguire
2020-05-12 5:56 ` [PATCH v2 bpf-next 4/7] printk: add type-printing %pT format specifier which uses BTF Alan Maguire
2020-05-13 23:05 ` Joe Perches
2020-05-13 23:07 ` Alexei Starovoitov
2020-05-13 23:22 ` Joe Perches
2020-05-14 23:43 ` Joe Perches
2020-05-15 0:09 ` Alexei Starovoitov
2020-05-15 0:21 ` Joe Perches
2020-05-14 0:45 ` Yonghong Song
2020-05-14 22:37 ` Alan Maguire
2020-05-15 0:39 ` Yonghong Song
2020-05-12 5:56 ` [PATCH v2 bpf-next 5/7] printk: extend test_printf to test %pT BTF-based format specifier Alan Maguire
2020-05-12 5:56 ` Alan Maguire [this message]
2020-05-14 0:53 ` [PATCH v2 bpf-next 6/7] bpf: add support for %pT format specifier for bpf_trace_printk() helper Yonghong Song
2020-05-18 9:10 ` Alan Maguire
2020-05-18 14:47 ` Yonghong Song
2020-05-12 5:56 ` [PATCH v2 bpf-next 7/7] bpf: add tests for %pT format specifier Alan Maguire
2020-05-15 0:21 ` Andrii Nakryiko
2020-05-13 22:24 ` [PATCH v2 bpf-next 0/7] bpf, printk: add BTF-based type printing Alexei Starovoitov
2020-05-13 22:48 ` Joe Perches
2020-05-13 22:50 ` Alexei Starovoitov
2020-05-13 23:23 ` Joe Perches
2020-05-14 17:46 ` Alan Maguire
2020-05-15 18:59 ` Yonghong Song
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