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

To: openldap-its@OpenLDAP.org
Subject: Re: (ITS#7713) Segmentation fault if the pagesize of the Operating system is not equal to 4096.
From: sumantk2@linux.vnet.ibm.com
Date: Tue, 1 Oct 2013 08:26:58 GMT
Auto-submitted: auto-generated (OpenLDAP-ITS)
On 10/01/2013 12:46 PM, Howard Chu wrote:
> 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.
>
Yes i have tried changing MDB_PAGESIZE to 65536 before reporting this 
and the segmentation fault still occured.
> 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.
>
Will try changing datatype and see ..But not sure whether it affects 
some other part of the code.
>>
>> 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
>>
>>
>
>
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