102 lines
3.7 KiB
Diff
102 lines
3.7 KiB
Diff
From FEDORA_PATCHES Mon Sep 17 00:00:00 2001
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From: Andrew Burgess <aburgess@redhat.com>
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Date: Mon, 27 Nov 2023 13:19:39 +0000
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Subject: gdb-rhbz-2232086-generate-dwarf-5-index-consistently.patch
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;; Back-port upstream commit 3644f41dc80 as part of a fix for
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;; non-deterministic gdb-index generation (RH BZ 2232086).
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gdb: generate dwarf-5 index identically as worker-thread count changes
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Similar to the previous commit, this commit ensures that the dwarf-5
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index files are generated identically as the number of worker-threads
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changes.
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Building the dwarf-5 index makes use of a closed hash table, the
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bucket_hash local within debug_names::build(). Entries are added to
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bucket_hash from m_name_to_value_set, which, in turn, is populated
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by calls to debug_names::insert() in write_debug_names. The insert
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calls are ordered based on the entries within the cooked_index, and
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the ordering within cooked_index depends on the number of worker
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threads that GDB is using.
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My proposal is to sort each chain within the bucket_hash closed hash
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table prior to using this to build the dwarf-5 index.
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The buckets within bucket_hash will always have the same ordering (for
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a given GDB build with a given executable), and by sorting the chains
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within each bucket, we can be sure that GDB will see each entry in a
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deterministic order.
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I've extended the index creation test to cover this case.
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Approved-By: Tom Tromey <tom@tromey.com>
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diff --git a/gdb/dwarf2/index-write.c b/gdb/dwarf2/index-write.c
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--- a/gdb/dwarf2/index-write.c
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+++ b/gdb/dwarf2/index-write.c
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@@ -452,6 +452,11 @@ class c_str_view
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return strcmp (m_cstr, other.m_cstr) == 0;
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}
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+ bool operator< (const c_str_view &other) const
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+ {
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+ return strcmp (m_cstr, other.m_cstr) < 0;
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+ }
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+
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/* Return the underlying C string. Note, the returned string is
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only a reference with lifetime of this object. */
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const char *c_str () const
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@@ -771,10 +776,18 @@ class debug_names
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}
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for (size_t bucket_ix = 0; bucket_ix < bucket_hash.size (); ++bucket_ix)
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{
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- const std::forward_list<hash_it_pair> &hashitlist
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- = bucket_hash[bucket_ix];
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+ std::forward_list<hash_it_pair> &hashitlist = bucket_hash[bucket_ix];
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if (hashitlist.empty ())
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continue;
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+
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+ /* Sort the items within each bucket. This ensures that the
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+ generated index files will be the same no matter the order in
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+ which symbols were added into the index. */
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+ hashitlist.sort ([] (const hash_it_pair &a, const hash_it_pair &b)
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+ {
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+ return a.it->first < b.it->first;
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+ });
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+
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uint32_t &bucket_slot = m_bucket_table[bucket_ix];
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/* The hashes array is indexed starting at 1. */
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store_unsigned_integer (reinterpret_cast<gdb_byte *> (&bucket_slot),
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diff --git a/gdb/testsuite/gdb.gdb/index-file.exp b/gdb/testsuite/gdb.gdb/index-file.exp
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--- a/gdb/testsuite/gdb.gdb/index-file.exp
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+++ b/gdb/testsuite/gdb.gdb/index-file.exp
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@@ -47,6 +47,9 @@ remote_exec host "mkdir -p ${dir1}"
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with_timeout_factor $timeout_factor {
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gdb_test_no_output "save gdb-index $dir1" \
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"create gdb-index file"
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+
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+ gdb_test_no_output "save gdb-index -dwarf-5 $dir1" \
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+ "create dwarf-index files"
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}
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# Close GDB.
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@@ -143,13 +146,16 @@ if { $worker_threads > 1 } {
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with_timeout_factor $timeout_factor {
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gdb_test_no_output "save gdb-index $dir2" \
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"create second gdb-index file"
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+
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+ gdb_test_no_output "save gdb-index -dwarf-5 $dir2" \
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+ "create second dwarf-index files"
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}
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# Close GDB.
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gdb_exit
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# Now check that the index files are identical.
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- foreach suffix { gdb-index } {
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+ foreach suffix { gdb-index debug_names debug_str } {
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set result \
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[remote_exec host \
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"cmp -s \"$dir1/${index_filename_base}.${suffix}\" \"$dir2/${index_filename_base}.${suffix}\""]
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