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Add support for lockless ringbuffer

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Release crash-7.2.9-2

Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
This commit is contained in:
Lianbo Jiang 2020-12-11 19:18:45 +08:00
parent cd525b14e6
commit 724c99dde0
3 changed files with 550 additions and 1 deletions
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9
crash.spec
View File

@ -4,7 +4,7 @@
Summary: Kernel analysis utility for live systems, netdump, diskdump, kdump, LKCD or mcore dumpfiles
Name: crash
Version: 7.2.9
Release: 1%{?dist}
Release: 2%{?dist}
License: GPLv3
Source0: https://github.com/crash-utility/crash/archive/crash-%{version}.tar.gz
Source1: http://ftp.gnu.org/gnu/gdb/gdb-7.6.tar.gz
@ -18,6 +18,8 @@ Provides: bundled(libiberty)
Provides: bundled(gdb) = 7.6
Patch0: lzo_snappy.patch
Patch1: use_system_readline_v3.patch
Patch2: printk-add-support-for-lockless-ringbuffer.patch
Patch3: printk-use-committed-finalized-state-values.patch
%description
The core analysis suite is a self-contained tool that can be used to
@ -39,6 +41,8 @@ offered by Mission Critical Linux, or the LKCD kernel patch.
%setup -n %{name}-%{version} -q
%patch0 -p1 -b lzo_snappy.patch
%patch1 -p1 -b use_system_readline_v3.patch
%patch2 -p1 -b printk-add-support-for-lockless-ringbuffer.patch
%patch3 -p1 -b printk-use-committed-finalized-state-values.patch
%build
# This package has an internal copy of GDB which has broken configure code for
@ -70,6 +74,9 @@ cp -p defs.h %{buildroot}%{_includedir}/crash
%{_includedir}/*
%changelog
* Fri Dec 11 2020 Lianbo Jiang <lijiang@redhat.com> - 7.2.9-2
- Add support for lockless ringbuffer
* Wed Nov 25 2020 Lianbo Jiang <lijiang@redhat.com> - 7.2.9-1
- Update to latest upstream release

442
printk-add-support-for-lockless-ringbuffer.patch Normal file
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@ -0,0 +1,442 @@
From a5531b24750e7949c35640d996ea14c0587938bc Mon Sep 17 00:00:00 2001
From: John Ogness <john.ogness@linutronix.de>
Date: Fri, 20 Nov 2020 05:56:59 +0000
Subject: [PATCH 1/2] printk: add support for lockless ringbuffer
Linux 5.10 introduces a new lockless ringbuffer. The new ringbuffer
is structured completely different to the previous iterations.
Add support for dumping the ringbuffer with the "log" command.
The new ringbuffer is detected based on the availability of
the "prb" symbol.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
---
Makefile | 5 ++
defs.h | 30 +++++++
kernel.c | 7 +-
printk.c | 256 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
symbols.c | 27 ++++++
5 files changed, 324 insertions(+), 1 deletion(-)
create mode 100644 printk.c
diff --git a/Makefile b/Makefile
index d1857190c2fb..f66eba7418d1 100644
--- a/Makefile
+++ b/Makefile
@@ -61,6 +61,7 @@ VMWARE_HFILES=vmware_vmss.h
CFILES=main.c tools.c global_data.c memory.c filesys.c help.c task.c \
kernel.c test.c gdb_interface.c configure.c net.c dev.c bpf.c \
+ printk.c \
alpha.c x86.c ppc.c ia64.c s390.c s390x.c s390dbf.c ppc64.c x86_64.c \
arm.c arm64.c mips.c sparc64.c \
extensions.c remote.c va_server.c va_server_v1.c symbols.c cmdline.c \
@@ -80,6 +81,7 @@ SOURCE_FILES=${CFILES} ${GENERIC_HFILES} ${MCORE_HFILES} \
OBJECT_FILES=main.o tools.o global_data.o memory.o filesys.o help.o task.o \
build_data.o kernel.o test.o gdb_interface.o net.o dev.o bpf.o \
+ printk.o \
alpha.o x86.o ppc.o ia64.o s390.o s390x.o s390dbf.o ppc64.o x86_64.o \
arm.o arm64.o mips.o sparc64.o \
extensions.o remote.o va_server.o va_server_v1.o symbols.o cmdline.o \
@@ -363,6 +365,9 @@ task.o: ${GENERIC_HFILES} task.c
kernel.o: ${GENERIC_HFILES} kernel.c
${CC} -c ${CRASH_CFLAGS} kernel.c ${WARNING_OPTIONS} ${WARNING_ERROR}
+printk.o: ${GENERIC_HFILES} printk.c
+ ${CC} -c ${CRASH_CFLAGS} printk.c ${WARNING_OPTIONS} ${WARNING_ERROR}
+
gdb_interface.o: ${GENERIC_HFILES} gdb_interface.c
${CC} -c ${CRASH_CFLAGS} gdb_interface.c ${WARNING_OPTIONS} ${WARNING_ERROR}
diff --git a/defs.h b/defs.h
index 95949507cae4..e1a18e9d0b4d 100644
--- a/defs.h
+++ b/defs.h
@@ -2106,6 +2106,28 @@ struct offset_table { /* stash of commonly-used offsets */
long irq_common_data_affinity;
long irq_desc_irq_common_data;
long uts_namespace_name;
+ long printk_info_seq;
+ long printk_info_ts_nsec;
+ long printk_info_text_len;
+ long printk_info_level;
+ long printk_info_caller_id;
+ long printk_info_dev_info;
+ long dev_printk_info_subsystem;
+ long dev_printk_info_device;
+ long prb_desc_ring;
+ long prb_text_data_ring;
+ long prb_desc_ring_count_bits;
+ long prb_desc_ring_descs;
+ long prb_desc_ring_infos;
+ long prb_desc_ring_head_id;
+ long prb_desc_ring_tail_id;
+ long prb_desc_state_var;
+ long prb_desc_text_blk_lpos;
+ long prb_data_blk_lpos_begin;
+ long prb_data_blk_lpos_next;
+ long prb_data_ring_size_bits;
+ long prb_data_ring_data;
+ long atomic_long_t_counter;
};
struct size_table { /* stash of commonly-used sizes */
@@ -2265,6 +2287,9 @@ struct size_table { /* stash of commonly-used sizes */
long xa_node;
long zram_table_entry;
long irq_common_data;
+ long printk_info;
+ long printk_ringbuffer;
+ long prb_desc;
};
struct array_table {
@@ -6696,6 +6721,11 @@ int vmware_guestdump_memory_dump(FILE *);
*/
int calc_kaslr_offset(ulong *, ulong *);
+/*
+ * printk.c
+ */
+void dump_lockless_record_log(int);
+
/*
* gnu_binutils.c
*/
diff --git a/kernel.c b/kernel.c
index 98716372c8be..e722ff941527 100644
--- a/kernel.c
+++ b/kernel.c
@@ -5042,6 +5042,11 @@ dump_log(int msg_flags)
struct syment *nsp;
int log_wrap, loglevel, log_buf_len;
+ if (kernel_symbol_exists("prb")) {
+ dump_lockless_record_log(msg_flags);
+ return;
+ }
+
if (kernel_symbol_exists("log_first_idx") &&
kernel_symbol_exists("log_next_idx")) {
dump_variable_length_record_log(msg_flags);
@@ -5289,7 +5294,7 @@ dump_log_entry(char *logptr, int msg_flags)
}
/*
- * Handle the new variable-length-record log_buf.
+ * Handle the variable-length-record log_buf.
*/
static void
dump_variable_length_record_log(int msg_flags)
diff --git a/printk.c b/printk.c
new file mode 100644
index 000000000000..f6d54ce9d0d8
--- /dev/null
+++ b/printk.c
@@ -0,0 +1,256 @@
+#include "defs.h"
+#include <ctype.h>
+
+#define DESC_SV_BITS (sizeof(unsigned long) * 8)
+#define DESC_COMMITTED_MASK (1UL << (DESC_SV_BITS - 1))
+#define DESC_REUSE_MASK (1UL << (DESC_SV_BITS - 2))
+#define DESC_FLAGS_MASK (DESC_COMMITTED_MASK | DESC_REUSE_MASK)
+#define DESC_ID_MASK (~DESC_FLAGS_MASK)
+
+/* convenience struct for passing many values to helper functions */
+struct prb_map {
+ char *prb;
+
+ char *desc_ring;
+ unsigned long desc_ring_count;
+ char *descs;
+ char *infos;
+
+ char *text_data_ring;
+ unsigned long text_data_ring_size;
+ char *text_data;
+};
+
+static void
+init_offsets(void)
+{
+ char *n;
+
+ n = "printk_info";
+ STRUCT_SIZE_INIT(printk_info, n);
+ MEMBER_OFFSET_INIT(printk_info_seq, n, "seq");
+ MEMBER_OFFSET_INIT(printk_info_ts_nsec, n, "ts_nsec");
+ MEMBER_OFFSET_INIT(printk_info_text_len, n, "text_len");
+ MEMBER_OFFSET_INIT(printk_info_level, n, "level");
+ MEMBER_OFFSET_INIT(printk_info_caller_id, n, "caller_id");
+ MEMBER_OFFSET_INIT(printk_info_dev_info, n, "dev_info");
+
+ n = "dev_printk_info";
+ MEMBER_OFFSET_INIT(dev_printk_info_subsystem, n, "subsystem");
+ MEMBER_OFFSET_INIT(dev_printk_info_device, n, "device");
+
+ n = "printk_ringbuffer";
+ STRUCT_SIZE_INIT(printk_ringbuffer, n);
+ MEMBER_OFFSET_INIT(prb_desc_ring, n, "desc_ring");
+ MEMBER_OFFSET_INIT(prb_text_data_ring, n, "text_data_ring");
+
+ n = "prb_desc_ring";
+ MEMBER_OFFSET_INIT(prb_desc_ring_count_bits, n, "count_bits");
+ MEMBER_OFFSET_INIT(prb_desc_ring_descs, n, "descs");
+ MEMBER_OFFSET_INIT(prb_desc_ring_infos, n, "infos");
+ MEMBER_OFFSET_INIT(prb_desc_ring_head_id, n, "head_id");
+ MEMBER_OFFSET_INIT(prb_desc_ring_tail_id, n, "tail_id");
+
+ n = "prb_desc";
+ STRUCT_SIZE_INIT(prb_desc, n);
+ MEMBER_OFFSET_INIT(prb_desc_state_var, n, "state_var");
+ MEMBER_OFFSET_INIT(prb_desc_text_blk_lpos, n, "text_blk_lpos");
+
+ n = "prb_data_blk_lpos";
+ MEMBER_OFFSET_INIT(prb_data_blk_lpos_begin, n, "begin");
+ MEMBER_OFFSET_INIT(prb_data_blk_lpos_next, n, "next");
+
+ n = "prb_data_ring";
+ MEMBER_OFFSET_INIT(prb_data_ring_size_bits, n, "size_bits");
+ MEMBER_OFFSET_INIT(prb_data_ring_data, n, "data");
+
+ n = "atomic_long_t";
+ MEMBER_OFFSET_INIT(atomic_long_t_counter, n, "counter");
+}
+
+static void
+dump_record(struct prb_map *m, unsigned long id, int msg_flags)
+{
+ unsigned short text_len;
+ unsigned long state_var;
+ unsigned int caller_id;
+ unsigned char level;
+ unsigned long begin;
+ unsigned long next;
+ char buf[BUFSIZE];
+ uint64_t ts_nsec;
+ ulonglong nanos;
+ ulonglong seq;
+ int ilen = 0, i;
+ char *desc, *info, *text, *p;
+ ulong rem;
+
+ desc = m->descs + ((id % m->desc_ring_count) * SIZE(prb_desc));
+
+ /* skip non-committed record */
+ state_var = ULONG(desc + OFFSET(prb_desc_state_var) +
+ OFFSET(atomic_long_t_counter));
+ if ((state_var & DESC_FLAGS_MASK) != DESC_COMMITTED_MASK)
+ return;
+
+ info = m->infos + ((id % m->desc_ring_count) * SIZE(printk_info));
+
+ seq = ULONGLONG(info + OFFSET(printk_info_seq));
+ caller_id = UINT(info + OFFSET(printk_info_caller_id));
+ if (CRASHDEBUG(1))
+ fprintf(fp, "seq: %llu caller_id: %x (%s: %u)\n", seq, caller_id,
+ caller_id & 0x80000000 ? "cpu" : "pid", caller_id & ~0x80000000);
+
+ text_len = USHORT(info + OFFSET(printk_info_text_len));
+
+ begin = ULONG(desc + OFFSET(prb_desc_text_blk_lpos) +
+ OFFSET(prb_data_blk_lpos_begin)) %
+ m->text_data_ring_size;
+ next = ULONG(desc + OFFSET(prb_desc_text_blk_lpos) +
+ OFFSET(prb_data_blk_lpos_next)) %
+ m->text_data_ring_size;
+
+ /* skip data-less text blocks */
+ if (begin == next)
+ goto out;
+
+ if ((msg_flags & SHOW_LOG_TEXT) == 0) {
+ ts_nsec = ULONGLONG(info + OFFSET(printk_info_ts_nsec));
+ nanos = (ulonglong)ts_nsec / (ulonglong)1000000000;
+ rem = (ulonglong)ts_nsec % (ulonglong)1000000000;
+ if (msg_flags & SHOW_LOG_CTIME) {
+ time_t t = kt->boot_date.tv_sec + nanos;
+ sprintf(buf, "[%s] ", ctime_tz(&t));
+ } else
+ sprintf(buf, "[%5lld.%06ld] ", nanos, rem/1000);
+
+ ilen += strlen(buf);
+ fprintf(fp, "%s", buf);
+ }
+
+ if (msg_flags & SHOW_LOG_LEVEL) {
+ level = UCHAR(info + OFFSET(printk_info_level)) >> 5;
+ sprintf(buf, "<%x>", level);
+ ilen += strlen(buf);
+ fprintf(fp, "%s", buf);
+ }
+
+ /* handle wrapping data block */
+ if (begin > next)
+ begin = 0;
+
+ /* skip over descriptor ID */
+ begin += sizeof(unsigned long);
+
+ /* handle truncated messages */
+ if (next - begin < text_len)
+ text_len = next - begin;
+
+ text = m->text_data + begin;
+
+ for (i = 0, p = text; i < text_len; i++, p++) {
+ if (*p == '\n')
+ fprintf(fp, "\n%s", space(ilen));
+ else if (isprint(*p) || isspace(*p))
+ fputc(*p, fp);
+ else
+ fputc('.', fp);
+ }
+
+ if (msg_flags & SHOW_LOG_DICT) {
+ text = info + OFFSET(printk_info_dev_info) +
+ OFFSET(dev_printk_info_subsystem);
+ if (strlen(text))
+ fprintf(fp, "\n%sSUBSYSTEM=%s", space(ilen), text);
+
+ text = info + OFFSET(printk_info_dev_info) +
+ OFFSET(dev_printk_info_device);
+ if (strlen(text))
+ fprintf(fp, "\n%sDEVICE=%s", space(ilen), text);
+ }
+out:
+ fprintf(fp, "\n");
+}
+
+/*
+ * Handle the lockless printk_ringbuffer.
+ */
+void
+dump_lockless_record_log(int msg_flags)
+{
+ unsigned long head_id;
+ unsigned long tail_id;
+ unsigned long kaddr;
+ unsigned long id;
+ struct prb_map m;
+
+ if (INVALID_SIZE(printk_info))
+ init_offsets();
+
+ /* setup printk_ringbuffer */
+ get_symbol_data("prb", sizeof(char *), &kaddr);
+ m.prb = GETBUF(SIZE(printk_ringbuffer));
+ if (!readmem(kaddr, KVADDR, m.prb, SIZE(printk_ringbuffer),
+ "printk_ringbuffer contents", RETURN_ON_ERROR|QUIET)) {
+ error(WARNING, "\ncannot read printk_ringbuffer contents\n");
+ goto out_prb;
+ }
+
+ /* setup descriptor ring */
+ m.desc_ring = m.prb + OFFSET(prb_desc_ring);
+ m.desc_ring_count = 1 << UINT(m.desc_ring + OFFSET(prb_desc_ring_count_bits));
+
+ kaddr = ULONG(m.desc_ring + OFFSET(prb_desc_ring_descs));
+ m.descs = GETBUF(SIZE(prb_desc) * m.desc_ring_count);
+ if (!readmem(kaddr, KVADDR, m.descs, SIZE(prb_desc) * m.desc_ring_count,
+ "prb_desc_ring contents", RETURN_ON_ERROR|QUIET)) {
+ error(WARNING, "\ncannot read prb_desc_ring contents\n");
+ goto out_descs;
+ }
+
+ kaddr = ULONG(m.desc_ring + OFFSET(prb_desc_ring_infos));
+ m.infos = GETBUF(SIZE(printk_info) * m.desc_ring_count);
+ if (!readmem(kaddr, KVADDR, m.infos, SIZE(printk_info) * m.desc_ring_count,
+ "prb_info_ring contents", RETURN_ON_ERROR|QUIET)) {
+ error(WARNING, "\ncannot read prb_info_ring contents\n");
+ goto out_infos;
+ }
+
+ /* setup text data ring */
+ m.text_data_ring = m.prb + OFFSET(prb_text_data_ring);
+ m.text_data_ring_size = 1 << UINT(m.text_data_ring + OFFSET(prb_data_ring_size_bits));
+
+ kaddr = ULONG(m.text_data_ring + OFFSET(prb_data_ring_data));
+ m.text_data = GETBUF(m.text_data_ring_size);
+ if (!readmem(kaddr, KVADDR, m.text_data, m.text_data_ring_size,
+ "prb_text_data_ring contents", RETURN_ON_ERROR|QUIET)) {
+ error(WARNING, "\ncannot read prb_text_data_ring contents\n");
+ goto out_text_data;
+ }
+
+ /* ready to go */
+
+ tail_id = ULONG(m.desc_ring + OFFSET(prb_desc_ring_tail_id) +
+ OFFSET(atomic_long_t_counter));
+ head_id = ULONG(m.desc_ring + OFFSET(prb_desc_ring_head_id) +
+ OFFSET(atomic_long_t_counter));
+
+ hq_open();
+
+ for (id = tail_id; id != head_id; id = (id + 1) & DESC_ID_MASK)
+ dump_record(&m, id, msg_flags);
+
+ /* dump head record */
+ dump_record(&m, id, msg_flags);
+
+ hq_close();
+
+out_text_data:
+ FREEBUF(m.text_data);
+out_infos:
+ FREEBUF(m.infos);
+out_descs:
+ FREEBUF(m.descs);
+out_prb:
+ FREEBUF(m.prb);
+}
diff --git a/symbols.c b/symbols.c
index b2f4eb5402d1..a51078d58e6b 100644
--- a/symbols.c
+++ b/symbols.c
@@ -10426,6 +10426,30 @@ dump_offset_table(char *spec, ulong makestruct)
OFFSET(log_level));
fprintf(fp, " log_flags_level: %ld\n",
OFFSET(log_flags_level));
+
+ fprintf(fp, " printk_info_seq: %ld\n", OFFSET(printk_info_seq));
+ fprintf(fp, " printk_info_ts_nseq: %ld\n", OFFSET(printk_info_ts_nsec));
+ fprintf(fp, " printk_info_text_len: %ld\n", OFFSET(printk_info_text_len));
+ fprintf(fp, " printk_info_level: %ld\n", OFFSET(printk_info_level));
+ fprintf(fp, " printk_info_caller_id: %ld\n", OFFSET(printk_info_caller_id));
+ fprintf(fp, " printk_info_dev_info: %ld\n", OFFSET(printk_info_dev_info));
+ fprintf(fp, " dev_printk_info_subsystem: %ld\n", OFFSET(dev_printk_info_subsystem));
+ fprintf(fp, " dev_printk_info_device: %ld\n", OFFSET(dev_printk_info_device));
+ fprintf(fp, " prb_desc_ring: %ld\n", OFFSET(prb_desc_ring));
+ fprintf(fp, " prb_text_data_ring: %ld\n", OFFSET(prb_text_data_ring));
+ fprintf(fp, " prb_desc_ring_count_bits: %ld\n", OFFSET(prb_desc_ring_count_bits));
+ fprintf(fp, " prb_desc_ring_descs: %ld\n", OFFSET(prb_desc_ring_descs));
+ fprintf(fp, " prb_desc_ring_infos: %ld\n", OFFSET(prb_desc_ring_infos));
+ fprintf(fp, " prb_desc_ring_head_id: %ld\n", OFFSET(prb_desc_ring_head_id));
+ fprintf(fp, " prb_desc_ring_tail_id: %ld\n", OFFSET(prb_desc_ring_tail_id));
+ fprintf(fp, " prb_desc_state_var: %ld\n", OFFSET(prb_desc_state_var));
+ fprintf(fp, " prb_desc_text_blk_lpos: %ld\n", OFFSET(prb_desc_text_blk_lpos));
+ fprintf(fp, " prb_data_blk_lpos_begin: %ld\n", OFFSET(prb_data_blk_lpos_begin));
+ fprintf(fp, " prb_data_blk_lpos_next: %ld\n", OFFSET(prb_data_blk_lpos_next));
+ fprintf(fp, " prb_data_ring_size_bits: %ld\n", OFFSET(prb_data_ring_size_bits));
+ fprintf(fp, " prb_data_ring_data: %ld\n", OFFSET(prb_data_ring_data));
+ fprintf(fp, " atomit_long_t_counter: %ld\n", OFFSET(atomic_long_t_counter));
+
fprintf(fp, " sched_rt_entity_my_q: %ld\n",
OFFSET(sched_rt_entity_my_q));
fprintf(fp, " task_group_parent: %ld\n",
@@ -10850,6 +10874,9 @@ dump_offset_table(char *spec, ulong makestruct)
SIZE(xarray));
fprintf(fp, " xa_node: %ld\n",
SIZE(xa_node));
+ fprintf(fp, " printk_info: %ld\n", SIZE(printk_info));
+ fprintf(fp, " printk_ringbuffer: %ld\n", SIZE(printk_ringbuffer));
+ fprintf(fp, " prb_desc: %ld\n", SIZE(prb_desc));
fprintf(fp, "\n array_table:\n");
--
2.17.1

100
printk-use-committed-finalized-state-values.patch Normal file
View File

@ -0,0 +1,100 @@
From 71e159c64000467e94e08aefc144f5e1cdaa4aa0 Mon Sep 17 00:00:00 2001
From: John Ogness <john.ogness@linutronix.de>
Date: Wed, 25 Nov 2020 05:27:53 +0106
Subject: [PATCH 2/2] printk: use committed/finalized state values
An addendum to the previous crash commit a5531b24750e.
The ringbuffer entries use 2 state values (committed and finalized)
rather than a single flag to represent being available for reading.
Copy the definitions and state lookup function directly from the
kernel source and use the new states.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
printk.c | 48 +++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 41 insertions(+), 7 deletions(-)
diff --git a/printk.c b/printk.c
index f6d54ce9d0d8..8658016e65bf 100644
--- a/printk.c
+++ b/printk.c
@@ -1,12 +1,6 @@
#include "defs.h"
#include <ctype.h>
-#define DESC_SV_BITS (sizeof(unsigned long) * 8)
-#define DESC_COMMITTED_MASK (1UL << (DESC_SV_BITS - 1))
-#define DESC_REUSE_MASK (1UL << (DESC_SV_BITS - 2))
-#define DESC_FLAGS_MASK (DESC_COMMITTED_MASK | DESC_REUSE_MASK)
-#define DESC_ID_MASK (~DESC_FLAGS_MASK)
-
/* convenience struct for passing many values to helper functions */
struct prb_map {
char *prb;
@@ -21,6 +15,44 @@ struct prb_map {
char *text_data;
};
+/*
+ * desc_state and DESC_* definitions taken from kernel source:
+ *
+ * kernel/printk/printk_ringbuffer.h
+ */
+
+/* The possible responses of a descriptor state-query. */
+enum desc_state {
+ desc_miss = -1, /* ID mismatch (pseudo state) */
+ desc_reserved = 0x0, /* reserved, in use by writer */
+ desc_committed = 0x1, /* committed by writer, could get reopened */
+ desc_finalized = 0x2, /* committed, no further modification allowed */
+ desc_reusable = 0x3, /* free, not yet used by any writer */
+};
+
+#define DESC_SV_BITS (sizeof(unsigned long) * 8)
+#define DESC_FLAGS_SHIFT (DESC_SV_BITS - 2)
+#define DESC_FLAGS_MASK (3UL << DESC_FLAGS_SHIFT)
+#define DESC_STATE(sv) (3UL & (sv >> DESC_FLAGS_SHIFT))
+#define DESC_ID_MASK (~DESC_FLAGS_MASK)
+#define DESC_ID(sv) ((sv) & DESC_ID_MASK)
+
+/*
+ * get_desc_state() taken from kernel source:
+ *
+ * kernel/printk/printk_ringbuffer.c
+ */
+
+/* Query the state of a descriptor. */
+static enum desc_state get_desc_state(unsigned long id,
+ unsigned long state_val)
+{
+ if (id != DESC_ID(state_val))
+ return desc_miss;
+
+ return DESC_STATE(state_val);
+}
+
static void
init_offsets(void)
{
@@ -74,6 +106,7 @@ dump_record(struct prb_map *m, unsigned long id, int msg_flags)
unsigned short text_len;
unsigned long state_var;
unsigned int caller_id;
+ enum desc_state state;
unsigned char level;
unsigned long begin;
unsigned long next;
@@ -90,7 +123,8 @@ dump_record(struct prb_map *m, unsigned long id, int msg_flags)
/* skip non-committed record */
state_var = ULONG(desc + OFFSET(prb_desc_state_var) +
OFFSET(atomic_long_t_counter));
- if ((state_var & DESC_FLAGS_MASK) != DESC_COMMITTED_MASK)
+ state = get_desc_state(id, state_var);
+ if (state != desc_committed && state != desc_finalized)
return;
info = m->infos + ((id % m->desc_ring_count) * SIZE(printk_info));
--
2.17.1