libbpf-tools: Make tools independent of vmlinux.h

Kernel structs vary in different versions. Let's define all relying
structs in core_fixes.bpf.h so that we can update vmlinux.h independently.
This is a preparaton for the RISC-V support.

Signed-off-by: Hengqi Chen <[email protected]>

Author: chenhengqi

libbpf-tools/biolatency.bpf.c

@@ -6,6 +6,7 @@
 #include <bpf/bpf_tracing.h>
 #include "biolatency.h"
 #include "bits.bpf.h"
+#include "core_fixes.bpf.h"
 
 #define MAX_ENTRIES	10240
 
@@ -19,10 +20,6 @@ const volatile bool targ_ms = false;
 const volatile bool filter_dev = false;
 const volatile __u32 targ_dev = 0;
 
-struct request_queue___x {
-	struct gendisk *disk;
-} __attribute__((preserve_access_index));
-
 struct {
 	__uint(type, BPF_MAP_TYPE_CGROUP_ARRAY);
 	__type(key, u32);
@@ -55,15 +52,9 @@ int trace_rq_start(struct request *rq, int issue)
 	u64 ts = bpf_ktime_get_ns();
 
 	if (filter_dev) {
-		struct request_queue___x *q = (void *)BPF_CORE_READ(rq, q);
-		struct gendisk *disk;
+		struct gendisk *disk = get_disk(rq);
 		u32 dev;
 
-		if (bpf_core_field_exists(q->disk))
-			disk = BPF_CORE_READ(q, disk);
-		else
-			disk = BPF_CORE_READ(rq, rq_disk);
-
 		dev = disk ? MKDEV(BPF_CORE_READ(disk, major),
 				BPF_CORE_READ(disk, first_minor)) : 0;
 		if (targ_dev != dev)
@@ -127,13 +118,7 @@ int BPF_PROG(block_rq_complete, struct request *rq, int error,
 		goto cleanup;
 
 	if (targ_per_disk) {
-		struct request_queue___x *q = (void *)BPF_CORE_READ(rq, q);
-		struct gendisk *disk;
-
-		if (bpf_core_field_exists(q->disk))
-			disk = BPF_CORE_READ(q, disk);
-		else
-			disk = BPF_CORE_READ(rq, rq_disk);
+		struct gendisk *disk = get_disk(rq);
 
 		hkey.dev = disk ? MKDEV(BPF_CORE_READ(disk, major),
 					BPF_CORE_READ(disk, first_minor)) : 0;

libbpf-tools/biopattern.bpf.c

@@ -31,7 +31,7 @@ int handle__block_rq_complete(void *args)
 		nr_sector = BPF_CORE_READ(ctx, nr_sector);
 		dev = BPF_CORE_READ(ctx, dev);
 	} else {
-		struct trace_event_raw_block_rq_complete *ctx = args;
+		struct trace_event_raw_block_rq_complete___x *ctx = args;
 		sector = BPF_CORE_READ(ctx, sector);
 		nr_sector = BPF_CORE_READ(ctx, nr_sector);
 		dev = BPF_CORE_READ(ctx, dev);

libbpf-tools/biosnoop.bpf.c

@@ -5,6 +5,7 @@
 #include <bpf/bpf_core_read.h>
 #include <bpf/bpf_tracing.h>
 #include "biosnoop.h"
+#include "core_fixes.bpf.h"
 
 #define MAX_ENTRIES	10240
 
@@ -15,10 +16,6 @@ const volatile __u32 targ_dev = 0;
 
 extern __u32 LINUX_KERNEL_VERSION __kconfig;
 
-struct request_queue___x {
-	struct gendisk *disk;
-} __attribute__((preserve_access_index));
-
 struct {
 	__uint(type, BPF_MAP_TYPE_CGROUP_ARRAY);
 	__type(key, u32);
@@ -95,13 +92,7 @@ int trace_rq_start(struct request *rq, bool insert)
 
 	stagep = bpf_map_lookup_elem(&start, &rq);
 	if (!stagep) {
-		struct request_queue___x *q = (void *)BPF_CORE_READ(rq, q);
-		struct gendisk *disk;
-
-		if (bpf_core_field_exists(q->disk))
-			disk = BPF_CORE_READ(q, disk);
-		else
-			disk = BPF_CORE_READ(rq, rq_disk);
+		struct gendisk *disk = get_disk(rq);
 
 		stage.dev = disk ? MKDEV(BPF_CORE_READ(disk, major),
 				BPF_CORE_READ(disk, first_minor)) : 0;

libbpf-tools/biostacks.bpf.c

@@ -7,17 +7,14 @@
 #include "biostacks.h"
 #include "bits.bpf.h"
 #include "maps.bpf.h"
+#include "core_fixes.bpf.h"
 
 #define MAX_ENTRIES	10240
 
 const volatile bool targ_ms = false;
 const volatile bool filter_dev = false;
 const volatile __u32 targ_dev = -1;
 
-struct request_queue___x {
-	struct gendisk *disk;
-} __attribute__((preserve_access_index));
-
 struct internal_rqinfo {
 	u64 start_ts;
 	struct rqinfo rqinfo;
@@ -43,15 +40,9 @@ static __always_inline
 int trace_start(void *ctx, struct request *rq, bool merge_bio)
 {
 	struct internal_rqinfo *i_rqinfop = NULL, i_rqinfo = {};
-	struct request_queue___x *q = (void *)BPF_CORE_READ(rq, q);
-	struct gendisk *disk;
+	struct gendisk *disk = get_disk(rq);
 	u32 dev;
 
-	if (bpf_core_field_exists(q->disk))
-		disk = BPF_CORE_READ(q, disk);
-	else
-		disk = BPF_CORE_READ(rq, rq_disk);
-
 	dev = disk ? MKDEV(BPF_CORE_READ(disk, major),
 			BPF_CORE_READ(disk, first_minor)) : 0;
 	if (filter_dev && targ_dev != dev)

libbpf-tools/bitesize.bpf.c

@@ -6,17 +6,14 @@
 #include <bpf/bpf_core_read.h>
 #include "bitesize.h"
 #include "bits.bpf.h"
+#include "core_fixes.bpf.h"
 
 const volatile char targ_comm[TASK_COMM_LEN] = {};
 const volatile bool filter_dev = false;
 const volatile __u32 targ_dev = 0;
 
 extern __u32 LINUX_KERNEL_VERSION __kconfig;
 
-struct request_queue___x {
-	struct gendisk *disk;
-} __attribute__((preserve_access_index));
-
 struct {
 	__uint(type, BPF_MAP_TYPE_HASH);
 	__uint(max_entries, 10240);
@@ -44,15 +41,9 @@ static int trace_rq_issue(struct request *rq)
 	u64 slot;
 
 	if (filter_dev) {
-		struct request_queue___x *q = (void *)BPF_CORE_READ(rq, q);
-		struct gendisk *disk;
+		struct gendisk *disk = get_disk(rq);
 		u32 dev;
 
-		if (bpf_core_field_exists(q->disk))
-			disk = BPF_CORE_READ(q, disk);
-		else
-			disk = BPF_CORE_READ(rq, rq_disk);
-
 		dev = disk ? MKDEV(BPF_CORE_READ(disk, major),
 				BPF_CORE_READ(disk, first_minor)) : 0;
 		if (targ_dev != dev)

libbpf-tools/core_fixes.bpf.h

@@ -13,6 +13,10 @@
  * see:
  *     https://github.com/torvalds/linux/commit/2f064a59a1
  */
+struct task_struct___o {
+	volatile long int state;
+} __attribute__((preserve_access_index));
+
 struct task_struct___x {
 	unsigned int __state;
 } __attribute__((preserve_access_index));
@@ -23,7 +27,7 @@ static __always_inline __s64 get_task_state(void *task)
 
 	if (bpf_core_field_exists(t->__state))
 		return BPF_CORE_READ(t, __state);
-	return BPF_CORE_READ((struct task_struct *)task, state);
+	return BPF_CORE_READ((struct task_struct___o *)task, state);
 }
 
 /**
@@ -32,6 +36,10 @@ static __always_inline __s64 get_task_state(void *task)
  * see:
  *     https://github.com/torvalds/linux/commit/309dca309fc3
  */
+struct bio___o {
+	struct gendisk *bi_disk;
+} __attribute__((preserve_access_index));
+
 struct bio___x {
 	struct block_device *bi_bdev;
 } __attribute__((preserve_access_index));
@@ -42,7 +50,7 @@ static __always_inline struct gendisk *get_gendisk(void *bio)
 
 	if (bpf_core_field_exists(b->bi_bdev))
 		return BPF_CORE_READ(b, bi_bdev, bd_disk);
-	return BPF_CORE_READ((struct bio *)bio, bi_disk);
+	return BPF_CORE_READ((struct bio___o *)bio, bi_disk);
 }
 
 /**
@@ -54,6 +62,12 @@ static __always_inline struct gendisk *get_gendisk(void *bio)
  * see:
  *     https://github.com/torvalds/linux/commit/d5869fdc189f
  */
+struct trace_event_raw_block_rq_complete___x {
+	dev_t dev;
+	sector_t sector;
+	unsigned int nr_sector;
+} __attribute__((preserve_access_index));
+
 struct trace_event_raw_block_rq_completion___x {
 	dev_t dev;
 	sector_t sector;
@@ -67,4 +81,32 @@ static __always_inline bool has_block_rq_completion()
 	return false;
 }
 
+/**
+ * commit d152c682f03c ("block: add an explicit ->disk backpointer to the
+ * request_queue") and commit f3fa33acca9f ("block: remove the ->rq_disk
+ * field in struct request") make some changes to `struct request` and
+ * `struct request_queue`. Now, to get the `struct gendisk *` field in a CO-RE
+ * way, we need both `struct request` and `struct request_queue`.
+ * see:
+ *     https://github.com/torvalds/linux/commit/d152c682f03c
+ *     https://github.com/torvalds/linux/commit/f3fa33acca9f
+ */
+struct request_queue___x {
+	struct gendisk *disk;
+} __attribute__((preserve_access_index));
+
+struct request___x {
+	struct request_queue___x *q;
+	struct gendisk *rq_disk;
+} __attribute__((preserve_access_index));
+
+static __always_inline struct gendisk *get_disk(void *request)
+{
+	struct request___x *r = request;
+
+	if (bpf_core_field_exists(r->rq_disk))
+		return BPF_CORE_READ(r, rq_disk);
+	return BPF_CORE_READ(r, q, disk);
+}
+
 #endif /* __CORE_FIXES_BPF_H */