[DTrace-devel] [PATCH v2] btf: support compilation in older environments
Kris Van Hees
kris.van.hees at oracle.com
Wed Nov 29 21:07:05 UTC 2023
Include a btf.h from a recent enough kernel to support all the type
kinds that the BTF-to-CTF convertor provides code for.
Note that the BTF-to-CTF convertor requires libctf. This patch also
ensures that the BTF-to-CTF convertor is not used when CTF is provided
by libdtrace-ctf (which is deprecated).
Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
---
include/linux/btf.h | 200 ++++++++++++++++++++++++++++++++++++++++++
libdtrace/Build | 5 +-
libdtrace/dt_btf.c | 6 +-
libdtrace/dt_btf.h | 1 -
libdtrace/dt_module.c | 15 +++-
5 files changed, 221 insertions(+), 6 deletions(-)
create mode 100644 include/linux/btf.h
diff --git a/include/linux/btf.h b/include/linux/btf.h
new file mode 100644
index 00000000..ec1798b6
--- /dev/null
+++ b/include/linux/btf.h
@@ -0,0 +1,200 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/* Copyright (c) 2018 Facebook */
+#ifndef _UAPI__LINUX_BTF_H__
+#define _UAPI__LINUX_BTF_H__
+
+#include <linux/types.h>
+
+#define BTF_MAGIC 0xeB9F
+#define BTF_VERSION 1
+
+struct btf_header {
+ __u16 magic;
+ __u8 version;
+ __u8 flags;
+ __u32 hdr_len;
+
+ /* All offsets are in bytes relative to the end of this header */
+ __u32 type_off; /* offset of type section */
+ __u32 type_len; /* length of type section */
+ __u32 str_off; /* offset of string section */
+ __u32 str_len; /* length of string section */
+};
+
+/* Max # of type identifier */
+#define BTF_MAX_TYPE 0x000fffff
+/* Max offset into the string section */
+#define BTF_MAX_NAME_OFFSET 0x00ffffff
+/* Max # of struct/union/enum members or func args */
+#define BTF_MAX_VLEN 0xffff
+
+struct btf_type {
+ __u32 name_off;
+ /* "info" bits arrangement
+ * bits 0-15: vlen (e.g. # of struct's members)
+ * bits 16-23: unused
+ * bits 24-28: kind (e.g. int, ptr, array...etc)
+ * bits 29-30: unused
+ * bit 31: kind_flag, currently used by
+ * struct, union, enum, fwd and enum64
+ */
+ __u32 info;
+ /* "size" is used by INT, ENUM, STRUCT, UNION, DATASEC and ENUM64.
+ * "size" tells the size of the type it is describing.
+ *
+ * "type" is used by PTR, TYPEDEF, VOLATILE, CONST, RESTRICT,
+ * FUNC, FUNC_PROTO, VAR, DECL_TAG and TYPE_TAG.
+ * "type" is a type_id referring to another type.
+ */
+ union {
+ __u32 size;
+ __u32 type;
+ };
+};
+
+#define BTF_INFO_KIND(info) (((info) >> 24) & 0x1f)
+#define BTF_INFO_VLEN(info) ((info) & 0xffff)
+#define BTF_INFO_KFLAG(info) ((info) >> 31)
+
+enum {
+ BTF_KIND_UNKN = 0, /* Unknown */
+ BTF_KIND_INT = 1, /* Integer */
+ BTF_KIND_PTR = 2, /* Pointer */
+ BTF_KIND_ARRAY = 3, /* Array */
+ BTF_KIND_STRUCT = 4, /* Struct */
+ BTF_KIND_UNION = 5, /* Union */
+ BTF_KIND_ENUM = 6, /* Enumeration up to 32-bit values */
+ BTF_KIND_FWD = 7, /* Forward */
+ BTF_KIND_TYPEDEF = 8, /* Typedef */
+ BTF_KIND_VOLATILE = 9, /* Volatile */
+ BTF_KIND_CONST = 10, /* Const */
+ BTF_KIND_RESTRICT = 11, /* Restrict */
+ BTF_KIND_FUNC = 12, /* Function */
+ BTF_KIND_FUNC_PROTO = 13, /* Function Proto */
+ BTF_KIND_VAR = 14, /* Variable */
+ BTF_KIND_DATASEC = 15, /* Section */
+ BTF_KIND_FLOAT = 16, /* Floating point */
+ BTF_KIND_DECL_TAG = 17, /* Decl Tag */
+ BTF_KIND_TYPE_TAG = 18, /* Type Tag */
+ BTF_KIND_ENUM64 = 19, /* Enumeration up to 64-bit values */
+
+ NR_BTF_KINDS,
+ BTF_KIND_MAX = NR_BTF_KINDS - 1,
+};
+
+/* For some specific BTF_KIND, "struct btf_type" is immediately
+ * followed by extra data.
+ */
+
+/* BTF_KIND_INT is followed by a u32 and the following
+ * is the 32 bits arrangement:
+ */
+#define BTF_INT_ENCODING(VAL) (((VAL) & 0x0f000000) >> 24)
+#define BTF_INT_OFFSET(VAL) (((VAL) & 0x00ff0000) >> 16)
+#define BTF_INT_BITS(VAL) ((VAL) & 0x000000ff)
+
+/* Attributes stored in the BTF_INT_ENCODING */
+#define BTF_INT_SIGNED (1 << 0)
+#define BTF_INT_CHAR (1 << 1)
+#define BTF_INT_BOOL (1 << 2)
+
+/* BTF_KIND_ENUM is followed by multiple "struct btf_enum".
+ * The exact number of btf_enum is stored in the vlen (of the
+ * info in "struct btf_type").
+ */
+struct btf_enum {
+ __u32 name_off;
+ __s32 val;
+};
+
+/* BTF_KIND_ARRAY is followed by one "struct btf_array" */
+struct btf_array {
+ __u32 type;
+ __u32 index_type;
+ __u32 nelems;
+};
+
+/* BTF_KIND_STRUCT and BTF_KIND_UNION are followed
+ * by multiple "struct btf_member". The exact number
+ * of btf_member is stored in the vlen (of the info in
+ * "struct btf_type").
+ */
+struct btf_member {
+ __u32 name_off;
+ __u32 type;
+ /* If the type info kind_flag is set, the btf_member offset
+ * contains both member bitfield size and bit offset. The
+ * bitfield size is set for bitfield members. If the type
+ * info kind_flag is not set, the offset contains only bit
+ * offset.
+ */
+ __u32 offset;
+};
+
+/* If the struct/union type info kind_flag is set, the
+ * following two macros are used to access bitfield_size
+ * and bit_offset from btf_member.offset.
+ */
+#define BTF_MEMBER_BITFIELD_SIZE(val) ((val) >> 24)
+#define BTF_MEMBER_BIT_OFFSET(val) ((val) & 0xffffff)
+
+/* BTF_KIND_FUNC_PROTO is followed by multiple "struct btf_param".
+ * The exact number of btf_param is stored in the vlen (of the
+ * info in "struct btf_type").
+ */
+struct btf_param {
+ __u32 name_off;
+ __u32 type;
+};
+
+enum {
+ BTF_VAR_STATIC = 0,
+ BTF_VAR_GLOBAL_ALLOCATED = 1,
+ BTF_VAR_GLOBAL_EXTERN = 2,
+};
+
+enum btf_func_linkage {
+ BTF_FUNC_STATIC = 0,
+ BTF_FUNC_GLOBAL = 1,
+ BTF_FUNC_EXTERN = 2,
+};
+
+/* BTF_KIND_VAR is followed by a single "struct btf_var" to describe
+ * additional information related to the variable such as its linkage.
+ */
+struct btf_var {
+ __u32 linkage;
+};
+
+/* BTF_KIND_DATASEC is followed by multiple "struct btf_var_secinfo"
+ * to describe all BTF_KIND_VAR types it contains along with it's
+ * in-section offset as well as size.
+ */
+struct btf_var_secinfo {
+ __u32 type;
+ __u32 offset;
+ __u32 size;
+};
+
+/* BTF_KIND_DECL_TAG is followed by a single "struct btf_decl_tag" to describe
+ * additional information related to the tag applied location.
+ * If component_idx == -1, the tag is applied to a struct, union,
+ * variable or function. Otherwise, it is applied to a struct/union
+ * member or a func argument, and component_idx indicates which member
+ * or argument (0 ... vlen-1).
+ */
+struct btf_decl_tag {
+ __s32 component_idx;
+};
+
+/* BTF_KIND_ENUM64 is followed by multiple "struct btf_enum64".
+ * The exact number of btf_enum64 is stored in the vlen (of the
+ * info in "struct btf_type").
+ */
+struct btf_enum64 {
+ __u32 name_off;
+ __u32 val_lo32;
+ __u32 val_hi32;
+};
+
+#endif /* _UAPI__LINUX_BTF_H__ */
diff --git a/libdtrace/Build b/libdtrace/Build
index 76fd32e4..cbeefe44 100644
--- a/libdtrace/Build
+++ b/libdtrace/Build
@@ -13,7 +13,6 @@ libdtrace-build_DIR := $(current-dir)
libdtrace-build_SOURCES = dt_aggregate.c \
dt_as.c \
dt_bpf.c \
- dt_btf.c \
dt_buf.c \
dt_cc.c \
dt_cg.c \
@@ -71,6 +70,10 @@ libdtrace-build_SOURCES = dt_aggregate.c \
dt_work.c \
dt_xlator.c
+ifdef HAVE_LIBCTF
+libdtrace-build_SOURCES += dt_btf.c
+endif
+
libdtrace-build_SRCDEPS := dt_grammar.h $(objdir)/dt_git_version.h
SHLIBS += libdtrace
diff --git a/libdtrace/dt_btf.c b/libdtrace/dt_btf.c
index 2cb26aa5..01630b9c 100644
--- a/libdtrace/dt_btf.c
+++ b/libdtrace/dt_btf.c
@@ -7,7 +7,6 @@
#include <assert.h>
#include <byteswap.h>
-#include <ctf.h>
#include <errno.h>
#include <stdio.h>
#include <sys/mman.h>
@@ -147,6 +146,8 @@ dt_btf_type_size(const char *ptr)
return size + vlen * sizeof(btf_var_secinfo_t);
case BTF_KIND_DECL_TAG:
return size + sizeof(btf_decl_tag_t);
+ case BTF_KIND_TYPE_TAG:
+ return size;
case BTF_KIND_ENUM64:
return size + vlen * sizeof(btf_enum64_t);
case BTF_KIND_PTR:
@@ -157,7 +158,6 @@ dt_btf_type_size(const char *ptr)
case BTF_KIND_RESTRICT:
case BTF_KIND_FUNC:
case BTF_KIND_FLOAT:
- case BTF_KIND_TYPE_TAG:
return size;
default:
return -EINVAL;
@@ -658,8 +658,8 @@ dt_btf_add_to_ctf(dtrace_hdl_t *dtp, dt_btf_t *btf, ctf_dict_t *ctf,
case BTF_KIND_DATASEC:
case BTF_KIND_DECL_TAG:
case BTF_KIND_TYPE_TAG:
- case BTF_KIND_FUNC:
case BTF_KIND_ENUM64:
+ case BTF_KIND_FUNC:
return btf->ctfids[0]; /* Ignored for CTF */
default:
return dt_ctf_error(dtp, ctf);
diff --git a/libdtrace/dt_btf.h b/libdtrace/dt_btf.h
index 3db4203a..863fa470 100644
--- a/libdtrace/dt_btf.h
+++ b/libdtrace/dt_btf.h
@@ -8,7 +8,6 @@
#ifndef _DT_BTF_H
#define _DT_BTF_H
-#include <ctf.h>
#include <dt_impl.h>
#ifdef __cplusplus
diff --git a/libdtrace/dt_module.c b/libdtrace/dt_module.c
index 41c5083e..1e730426 100644
--- a/libdtrace/dt_module.c
+++ b/libdtrace/dt_module.c
@@ -26,9 +26,12 @@
#include <dt_kernel_module.h>
#include <dt_module.h>
#include <dt_impl.h>
-#include <dt_btf.h>
#include <dt_string.h>
+#ifdef HAVE_LIBCTF
+# include <dt_btf.h>
+#endif
+
#define KSYM_NAME_MAX 128 /* from kernel/scripts/kallsyms.c */
#define GZCHUNKSIZE (1024*512) /* gzip uncompression chunk size */
@@ -827,6 +830,7 @@ dt_kern_module_init(dtrace_hdl_t *dtp, dt_module_t *dmp)
return 0;
}
+#ifdef HAVE_LIBCTF
static void
dt_kern_module_ctf_from_btf(dtrace_hdl_t *dtp, dt_module_t *dmp)
{
@@ -848,6 +852,7 @@ dt_kern_module_ctf_from_btf(dtrace_hdl_t *dtp, dt_module_t *dmp)
else
dmp->dm_flags |= DT_DM_CTF_ARCHIVED;
}
+#endif
/*
* Determine the location of a kernel module's CTF data.
@@ -867,6 +872,7 @@ dt_kern_module_find_ctf(dtrace_hdl_t *dtp, dt_module_t *dmp)
dt_kern_module_init(dtp, dmp);
}
+#ifdef HAVE_LIBCTF
/*
* If we already know that our CTF data is derived from BTF data (i.e.
* there is no CTF archive for the runtime kernel), there is no point
@@ -876,6 +882,7 @@ dt_kern_module_find_ctf(dtrace_hdl_t *dtp, dt_module_t *dmp)
dt_kern_module_ctf_from_btf(dtp, dmp);
return;
}
+#endif
/*
* Kernel modules' CTF can be in one of two places: the CTF archive or
@@ -923,6 +930,7 @@ dt_kern_module_find_ctf(dtrace_hdl_t *dtp, dt_module_t *dmp)
ctfa_name);
}
} else {
+#ifdef HAVE_LIBCTF
dt_dprintf("Cannot open CTF archive %s: %s; "
"trying BTF.\n",
ctfa_name, ctf_errmsg(dtp->dt_ctferr));
@@ -933,6 +941,11 @@ dt_kern_module_find_ctf(dtrace_hdl_t *dtp, dt_module_t *dmp)
*/
dt_kern_module_ctf_from_btf(dtp,
dt_module_lookup_by_name(dtp, "vmlinux"));
+#else
+ dt_dprintf("Cannot open CTF archive %s: %s; "
+ "looking for in-module CTF instead.\n",
+ ctfa_name, ctf_errmsg(dtp->dt_ctferr));
+#endif
return;
}
--
2.42.0
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