Re: (ITS#7713) Segmentation fault if the pagesize of the Operating system is not equal to 4096.

[hyc@symas.com]

sumantk2@linux.vnet.ibm.com wrote:
> Full_Name: sumanth k
> Version: 2.4.35 to any recent version with mdb support
> OS: Linux - ppc64
> URL: ftp://ftp.openldap.org/incoming/
> Submission from: (NULL) (122.248.161.59)
>
>
> The pagesize of Linux for x86 and s390x architecture is 4096. Whereas in Powerpc
> <ppc64> , the pagesize is by default 65536. So when the pagesize is not equal to
> 4096, the segmentation fault occurs. So tried to compile the powerpc64 kernel
> with page size of 4096 and the problem disappears and runs smoothly. But by
> default the powerpc64 architecture runs with 65536 pagesize . So there is some
> problem in mdb_env_open2() function in mdb.c when the pagesize is not equal to
> 4096.

Thanks for the report. I believe you should be able to instead change the 
definition of MDB_PAGESIZE to 65536, instead of forcing your machine to use 
4096 byte pages.

There are other problems though; we use an unsigned short for page offsets. 
I'm not sure the assert that you tripped will succeed in this case.

>
> These are my observations :
>
>
> Compiled the source with -O0 optimization .
> /home/openldap-2.4.36/tests/../servers/slapd/slapd -s0 -f
> /home/openldap-2.4.36/tests/testrun/slapd.1.conf -h ldap://localhost:9011/ -d
> 0x4105
>
> ./scripts/test000-rootdse: line 31: 19059 Aborted                 (core dumped)
> $SLAPD -f $CONF1 -h $URI1 -d $LVL $TIMING > $LOG1 2>&1
>
> Core file :
> bash-4.2# cat .gdbinit
> b mdb_db_open
> b mdb_env_open
> b mdb_env_open2
> b mdb_txn_begin
> b mdb_txn_renew0
> b mdb_dbi_open
> b mdb_cursor_init
> b mdb_cursor_set
> b mdb_page_search
> b mdb_page_get
> b mdb_page_search_root
> r -s0 -f /home/openldap-2.4.36/tests/testrun/slapd.1.conf -h
> ldap://localhost:9011/ -d 0x4105
>
>
> # Core was generated by `/home/openldap-2.4.36/tests/../servers/slapd/slapd -s0
> -f /home/openldap-2.4.36'.
> Program terminated with signal 6, Aborted.
> #0  0x00001fffff7adb70 in .raise () from /lib64/libc.so.6
> Missing separate debuginfos, use: debuginfo-install
> cyrus-sasl-lib-2.1.26-8.mcp8_0.2.ppc64 cyrus-sasl-md5-2.1.26-8.mcp8_0.2.ppc64
> glibc-2.17-4.mcp8_0.6.ppc64 keyutils-libs-1.5.5-4.mcp8_0.2.ppc64
> krb5-libs-1.11.3-1.mcp8_0.2.ppc64 libcom_err-1.42.7-2.mcp8_0.1.ppc64
> libdb-5.3.21-8.mcp8_0.4.ppc64 libselinux-2.1.13-15.mcp8_0.3.ppc64
> nss-softokn-freebl-3.14.3-1.mcp8_0.2.ppc64 openssl-libs-1.0.1e-4.mcp8_0.1.ppc64
> pcre-8.32-7.mcp8_0.2.ppc64 zlib-1.2.7-10.mcp8_0.1.ppc64
> (gdb) where
> #0  0x00001fffff7adb70 in .raise () from /lib64/libc.so.6
> #1  0x00001fffff7afb64 in .abort () from /lib64/libc.so.6
> #2  0x00001fffff7a455c in .__assert_fail_base () from /lib64/libc.so.6
> #3  0x00001fffff7a464c in .__assert_fail () from /lib64/libc.so.6
> #4  0x00000000101498cc in mdb_node_add (mc=0x3fffe89a7d40, indx=0,
> key=0x3fffe89a7d20, data=0x3fffe89a7d30, pgno=0, flags=2) at
> ./../../../libraries/liblmdb/mdb.c:6160
> #5  0x000000001014882c in mdb_cursor_put (mc=0x3fffe89a7d40, key=0x3fffe89a7d20,
> data=0x3fffe89a7d30, flags=2) at ./../../../libraries/liblmdb/mdb.c:5877
> #6  0x00000000101516a8 in mdb_dbi_open (txn=0x1000f675980, name=0x1027b9c8
> "ad2i", flags=262152, dbi=0x1fffff0800a0) at
> ./../../../libraries/liblmdb/mdb.c:7902
> #7  0x0000000010139cd4 in mdb_db_open (be=0x1000f4f83a0, cr=0x3fffe89a81c0) at
> init.c:207
> #8  0x0000000010050e34 in backend_startup_one (be=0x1000f4f83a0,
> cr=0x3fffe89a81c0) at backend.c:224
> #9  0x0000000010051588 in backend_startup (be=0x1000f4f83a0) at backend.c:325
> #10 0x0000000010089a7c in slap_startup (be=0x0) at init.c:219
> #11 0x000000001000a9c8 in main (argc=8, argv=0x3fffe89a8958) at main.c:991
>
>
>
> Here is the error message :
>
> #/home/openldap-2.4.36/tests/../servers/slapd/slapd -s0 -f
> /home/openldap-2.4.36/tests/testrun/slapd.1.conf -h ldap://localhost:9011/ -d
> 0x4105
> (...some messages...)
> 524a2fe1 mdb_db_open: database "o=OpenLDAP Project,l=Internet":
> dbenv_open(/home/openldap-2.4.36/tests/testrun/db.1.a).
> slapd: ./../../../libraries/liblmdb/mdb.c:6160: mdb_node_add: Assertion
> `mp->mp_pb.pb.pb_upper >= mp->mp_pb.pb.pb_lower' failed. < === fails in assert()
> ;
> Aborted (core dumped)
>
>
>
> Some of my observation :
>
> in this file libraries/liblmdb/mdb.c
> in X86 :  rc = mdb_cursor_set(&mc, &key, &data, MDB_SET, &exact); the value of
> rc = MD_SUCCESS, but for ppc64 it is MDB_NOTFOUND. This is due to the fact that
> md_root != 2
>
> The value of md_root=2 for env->me_metas[1]->mm_dbs in X86 , but some huge value
> in ppc64. The value of md_pad = 4096 in x86 and 65536 in ppc64 .
>
> in x86:
>
> Breakpoint 2, mdb_txn_begin (env=0x9c5050, parent=0x0, flags=0,
> ret=0x7fffffffdf98) at ./../../../libraries/liblmdb/mdb.c:2219
> 2219		int rc, size, tsize = sizeof(MDB_txn);
> (gdb) p env->me_metas[1]->mm_dbs
> $1 = {{md_pad = 4096, md_flags = 8, md_depth = 0, md_branch_pages = 0,
> md_leaf_pages = 0, md_overflow_pages = 0, md_entries = 0, md_root =
> 18446744073709551615}, {md_pad = 0, md_flags = 0,
>      md_depth = 1, md_branch_pages = 0, md_leaf_pages = 1, md_overflow_pages = 0,
> md_entries = 4, md_root = 2}}
> (gdb) p env->me_metas[0]->mm_dbs
> $2 = {{md_pad = 4096, md_flags = 8, md_depth = 0, md_branch_pages = 0,
> md_leaf_pages = 0, md_overflow_pages = 0, md_entries = 0, md_root =
> 18446744073709551615}, {md_pad = 0, md_flags = 0,
>      md_depth = 0, md_branch_pages = 0, md_leaf_pages = 0, md_overflow_pages = 0,
> md_entries = 0, md_root = 18446744073709551615}}
>
>
> in ppc64:
>
> Breakpoint 2, mdb_txn_begin (env=0x10493ef0, parent=0x0, flags=0,
> ret=0x3fffffffe590) at ./../../../libraries/liblmdb/mdb.c:2219
> 2219            int rc, size, tsize = sizeof(MDB_txn);
> (gdb) p env->me_metas[0]->mm_dbs
> $1 = {{md_pad = 65536, md_flags = 8, md_depth = 0, md_branch_pages = 0,
> md_leaf_pages = 0, md_overflow_pages = 0, md_entries = 0, md_root =
> 18446744073709551615}, {md_pad = 0, md_flags = 0,
>      md_depth = 0, md_branch_pages = 0, md_leaf_pages = 0, md_overflow_pages = 0,
> md_entries = 0, md_root = 18446744073709551615}}
> (gdb) p env->me_metas[1]->mm_dbs
> $2 = {{md_pad = 65536, md_flags = 8, md_depth = 0, md_branch_pages = 0,
> md_leaf_pages = 0, md_overflow_pages = 0, md_entries = 0, md_root =
> 18446744073709551615}, {md_pad = 0, md_flags = 0,
>      md_depth = 0, md_branch_pages = 0, md_leaf_pages = 0, md_overflow_pages = 0,
> md_entries = 0, md_root = 18446744073709551615}}
>
>
>
>
> # From further investigation , the value of env->me_metas[1] is initialized in
> mdb_env_open2() at :
>
> p = (MDB_page *)env->me_map;
> env->me_metas[0] = METADATA(p);
> env->me_metas[1] = (MDB_meta *)((char *)env->me_metas[0] + meta.mm_psize);
>
> Here the meta.mm_psize in ppc64 is 65536 , hence there is some problem.. If the
> value of meta.mm_psize is 4096 , then everything works fine.
>
>
> As i dont have deep knowledge in openldap ,some help is needed.
>
> Thank you,
> Sumanth K
>
>


-- 
   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
   Chief Architect, OpenLDAP  http://www.openldap.org/project/