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This commit fixes a set of issues related to the use of the SQL functions in this module when the caller is able to pass down raw page data as input argument: - The page size check was fuzzy in a couple of places, sometimes looking after only a sub-range, but what we are looking for is an exact match on BLCKSZ. After considering a few options here, I have settled down to do a generalization of get_page_from_raw(). Most of the SQL functions already used that, and this is not strictly required if not accessing an 8-byte-wide value from a raw page, but this feels safer in the long run for alignment-picky environment, particularly if a code path begins to access such values. This also reduces the number of strings that need to be translated. - The BRIN function brin_page_items() uses a Relation but it did not check the access method of the opened index, potentially leading to crashes. All the other functions in need of a Relation already did that. - Some code paths could fail on elog(), but we should to use ereport() for failures that can be triggered by the user. Tests are added to stress all the cases that are fixed as of this commit, with some junk raw pages (\set VERBOSITY ensures that this works across all page sizes) and unexpected index types when functions open relations. Author: Michael Paquier, Justin Prysby Discussion: https://postgr.es/m/20220218030020.GA1137@telsasoft.com Backpatch-through: 10
301 lines
7.7 KiB
C
301 lines
7.7 KiB
C
/*-------------------------------------------------------------------------
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*
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* rawpage.c
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* Functions to extract a raw page as bytea and inspect it
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*
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* Access-method specific inspection functions are in separate files.
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*
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* Copyright (c) 2007-2018, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* contrib/pageinspect/rawpage.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "pageinspect.h"
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#include "access/htup_details.h"
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#include "catalog/namespace.h"
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#include "catalog/pg_type.h"
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#include "funcapi.h"
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#include "miscadmin.h"
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#include "storage/bufmgr.h"
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#include "storage/checksum.h"
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#include "utils/builtins.h"
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#include "utils/pg_lsn.h"
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#include "utils/rel.h"
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#include "utils/varlena.h"
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PG_MODULE_MAGIC;
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static bytea *get_raw_page_internal(text *relname, ForkNumber forknum,
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BlockNumber blkno);
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/*
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* get_raw_page
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*
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* Returns a copy of a page from shared buffers as a bytea
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*/
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PG_FUNCTION_INFO_V1(get_raw_page);
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Datum
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get_raw_page(PG_FUNCTION_ARGS)
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{
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text *relname = PG_GETARG_TEXT_PP(0);
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uint32 blkno = PG_GETARG_UINT32(1);
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bytea *raw_page;
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/*
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* We don't normally bother to check the number of arguments to a C
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* function, but here it's needed for safety because early 8.4 beta
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* releases mistakenly redefined get_raw_page() as taking three arguments.
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*/
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if (PG_NARGS() != 2)
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ereport(ERROR,
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(errmsg("wrong number of arguments to get_raw_page()"),
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errhint("Run the updated pageinspect.sql script.")));
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raw_page = get_raw_page_internal(relname, MAIN_FORKNUM, blkno);
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PG_RETURN_BYTEA_P(raw_page);
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}
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/*
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* get_raw_page_fork
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*
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* Same, for any fork
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*/
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PG_FUNCTION_INFO_V1(get_raw_page_fork);
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Datum
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get_raw_page_fork(PG_FUNCTION_ARGS)
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{
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text *relname = PG_GETARG_TEXT_PP(0);
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text *forkname = PG_GETARG_TEXT_PP(1);
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uint32 blkno = PG_GETARG_UINT32(2);
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bytea *raw_page;
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ForkNumber forknum;
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forknum = forkname_to_number(text_to_cstring(forkname));
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raw_page = get_raw_page_internal(relname, forknum, blkno);
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PG_RETURN_BYTEA_P(raw_page);
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}
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/*
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* workhorse
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*/
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static bytea *
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get_raw_page_internal(text *relname, ForkNumber forknum, BlockNumber blkno)
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{
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bytea *raw_page;
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RangeVar *relrv;
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Relation rel;
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char *raw_page_data;
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Buffer buf;
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if (!superuser())
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ereport(ERROR,
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(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
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(errmsg("must be superuser to use raw functions"))));
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relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
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rel = relation_openrv(relrv, AccessShareLock);
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/* Check that this relation has storage */
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if (rel->rd_rel->relkind == RELKIND_VIEW)
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ereport(ERROR,
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(errcode(ERRCODE_WRONG_OBJECT_TYPE),
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errmsg("cannot get raw page from view \"%s\"",
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RelationGetRelationName(rel))));
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if (rel->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
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ereport(ERROR,
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(errcode(ERRCODE_WRONG_OBJECT_TYPE),
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errmsg("cannot get raw page from composite type \"%s\"",
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RelationGetRelationName(rel))));
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if (rel->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
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ereport(ERROR,
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(errcode(ERRCODE_WRONG_OBJECT_TYPE),
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errmsg("cannot get raw page from foreign table \"%s\"",
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RelationGetRelationName(rel))));
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if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
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ereport(ERROR,
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(errcode(ERRCODE_WRONG_OBJECT_TYPE),
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errmsg("cannot get raw page from partitioned table \"%s\"",
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RelationGetRelationName(rel))));
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if (rel->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
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ereport(ERROR,
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(errcode(ERRCODE_WRONG_OBJECT_TYPE),
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errmsg("cannot get raw page from partitioned index \"%s\"",
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RelationGetRelationName(rel))));
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/*
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* Reject attempts to read non-local temporary relations; we would be
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* likely to get wrong data since we have no visibility into the owning
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* session's local buffers.
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*/
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if (RELATION_IS_OTHER_TEMP(rel))
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ereport(ERROR,
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(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
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errmsg("cannot access temporary tables of other sessions")));
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if (blkno >= RelationGetNumberOfBlocksInFork(rel, forknum))
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ereport(ERROR,
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(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
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errmsg("block number %u is out of range for relation \"%s\"",
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blkno, RelationGetRelationName(rel))));
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/* Initialize buffer to copy to */
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raw_page = (bytea *) palloc(BLCKSZ + VARHDRSZ);
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SET_VARSIZE(raw_page, BLCKSZ + VARHDRSZ);
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raw_page_data = VARDATA(raw_page);
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/* Take a verbatim copy of the page */
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buf = ReadBufferExtended(rel, forknum, blkno, RBM_NORMAL, NULL);
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LockBuffer(buf, BUFFER_LOCK_SHARE);
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memcpy(raw_page_data, BufferGetPage(buf), BLCKSZ);
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LockBuffer(buf, BUFFER_LOCK_UNLOCK);
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ReleaseBuffer(buf);
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relation_close(rel, AccessShareLock);
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return raw_page;
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}
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/*
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* get_page_from_raw
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*
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* Get a palloc'd, maxalign'ed page image from the result of get_raw_page()
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*
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* On machines with MAXALIGN = 8, the payload of a bytea is not maxaligned,
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* since it will start 4 bytes into a palloc'd value. On alignment-picky
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* machines, this will cause failures in accesses to 8-byte-wide values
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* within the page. We don't need to worry if accessing only 4-byte or
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* smaller fields, but when examining a struct that contains 8-byte fields,
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* use this function for safety.
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*/
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Page
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get_page_from_raw(bytea *raw_page)
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{
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Page page;
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int raw_page_size;
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raw_page_size = VARSIZE_ANY_EXHDR(raw_page);
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if (raw_page_size != BLCKSZ)
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ereport(ERROR,
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(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
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errmsg("invalid page size"),
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errdetail("Expected %d bytes, got %d.",
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BLCKSZ, raw_page_size)));
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page = palloc(raw_page_size);
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memcpy(page, VARDATA_ANY(raw_page), raw_page_size);
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return page;
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}
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/*
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* page_header
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*
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* Allows inspection of page header fields of a raw page
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*/
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PG_FUNCTION_INFO_V1(page_header);
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Datum
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page_header(PG_FUNCTION_ARGS)
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{
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bytea *raw_page = PG_GETARG_BYTEA_P(0);
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TupleDesc tupdesc;
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Datum result;
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HeapTuple tuple;
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Datum values[9];
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bool nulls[9];
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PageHeader page;
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XLogRecPtr lsn;
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if (!superuser())
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ereport(ERROR,
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(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
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(errmsg("must be superuser to use raw page functions"))));
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page = (PageHeader) get_page_from_raw(raw_page);
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/* Build a tuple descriptor for our result type */
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if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
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elog(ERROR, "return type must be a row type");
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/* Extract information from the page header */
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lsn = PageGetLSN(page);
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/* pageinspect >= 1.2 uses pg_lsn instead of text for the LSN field. */
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if (TupleDescAttr(tupdesc, 0)->atttypid == TEXTOID)
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{
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char lsnchar[64];
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snprintf(lsnchar, sizeof(lsnchar), "%X/%X",
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(uint32) (lsn >> 32), (uint32) lsn);
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values[0] = CStringGetTextDatum(lsnchar);
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}
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else
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values[0] = LSNGetDatum(lsn);
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values[1] = UInt16GetDatum(page->pd_checksum);
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values[2] = UInt16GetDatum(page->pd_flags);
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values[3] = UInt16GetDatum(page->pd_lower);
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values[4] = UInt16GetDatum(page->pd_upper);
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values[5] = UInt16GetDatum(page->pd_special);
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values[6] = UInt16GetDatum(PageGetPageSize(page));
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values[7] = UInt16GetDatum(PageGetPageLayoutVersion(page));
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values[8] = TransactionIdGetDatum(page->pd_prune_xid);
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/* Build and return the tuple. */
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memset(nulls, 0, sizeof(nulls));
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tuple = heap_form_tuple(tupdesc, values, nulls);
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result = HeapTupleGetDatum(tuple);
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PG_RETURN_DATUM(result);
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}
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/*
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* page_checksum
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*
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* Compute checksum of a raw page
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*/
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PG_FUNCTION_INFO_V1(page_checksum);
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Datum
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page_checksum(PG_FUNCTION_ARGS)
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{
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bytea *raw_page = PG_GETARG_BYTEA_P(0);
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uint32 blkno = PG_GETARG_INT32(1);
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Page page;
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if (!superuser())
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ereport(ERROR,
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(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
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(errmsg("must be superuser to use raw page functions"))));
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page = get_page_from_raw(raw_page);
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PG_RETURN_INT16(pg_checksum_page((char *) page, blkno));
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}
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