diff --git a/crash.spec b/crash.spec index 088fc33..d410cf3 100644 --- a/crash.spec +++ b/crash.spec @@ -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 - 7.2.9-2 +- Add support for lockless ringbuffer + * Wed Nov 25 2020 Lianbo Jiang - 7.2.9-1 - Update to latest upstream release diff --git a/printk-add-support-for-lockless-ringbuffer.patch b/printk-add-support-for-lockless-ringbuffer.patch new file mode 100644 index 0000000..bdfb0ef --- /dev/null +++ b/printk-add-support-for-lockless-ringbuffer.patch @@ -0,0 +1,442 @@ +From a5531b24750e7949c35640d996ea14c0587938bc Mon Sep 17 00:00:00 2001 +From: John Ogness +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 +Signed-off-by: Kazuhito Hagio +--- + 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 ++ ++#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 + diff --git a/printk-use-committed-finalized-state-values.patch b/printk-use-committed-finalized-state-values.patch new file mode 100644 index 0000000..d89b866 --- /dev/null +++ b/printk-use-committed-finalized-state-values.patch @@ -0,0 +1,100 @@ +From 71e159c64000467e94e08aefc144f5e1cdaa4aa0 Mon Sep 17 00:00:00 2001 +From: John Ogness +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 +Signed-off-by: Nikolay Borisov +--- + 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 + +-#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 +