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<p>Hi, Sergey,</p>
<p>thanks for the patch! Please see my comments below.</p>
<p>Sergey<br>
</p>
<div class="moz-cite-prefix">On 6/12/25 12:36, Sergey Kaplun wrote:<br>
</div>
<blockquote type="cite"
cite="mid:20250612093651.7552-1-skaplun@tarantool.org">
<pre wrap="" class="moz-quote-pre">From: Mike Pall <mike>
Reported by caohongqing.
Fix contributed by Peter Cawley.
(cherry picked from commit 8fbd576fb9414a5fa70dfa6069733d3416a78269)
`asm_hrefk()` uses the check for the offset for the corresponding node
structure. However, the target load is performed from its inner `key`
field with the offset 8. In the case of a huge table, it is possible
that the offset of the node (4095 * 8) is less than 4096 * 8 and can be
emitted via the corresponding instruction as an immediate offset, but
the offset of the `key` field is not. This leads to the corresponding
assertion failure in `emit_lso()`.</pre>
</blockquote>
<p>The issue [1] contains yet another fix in the same place [2]. We
decided to backport the patch</p>
<p>separately. But please mention this in commit message.<br>
</p>
<p><br>
</p>
<p>1. <a class="moz-txt-link-freetext" href="https://github.com/LuaJIT/LuaJIT/issues/1026">https://github.com/LuaJIT/LuaJIT/issues/1026</a><br>
</p>
<p>2.
<a class="moz-txt-link-freetext" href="https://github.com/LuaJIT/LuaJIT/commit/93ce12ee15abf28ef4cb24ae7e4b8a5b73d75c85">https://github.com/LuaJIT/LuaJIT/commit/93ce12ee15abf28ef4cb24ae7e4b8a5b73d75c85</a></p>
<p><br>
</p>
<blockquote type="cite"
cite="mid:20250612093651.7552-1-skaplun@tarantool.org">
<pre wrap="" class="moz-quote-pre">
This patch fixes this behaviour by the correct check.
Sergey Kaplun:
* added the description and the test for the problem
Part of tarantool/tarantool#11278
---
Related issues:
* <a class="moz-txt-link-freetext" href="https://github.com/LuaJIT/LuaJIT/issues/1026">https://github.com/LuaJIT/LuaJIT/issues/1026</a>
* <a class="moz-txt-link-freetext" href="https://github.com/tarantool/tarantool/issues/11278">https://github.com/tarantool/tarantool/issues/11278</a>
Branch: <a class="moz-txt-link-freetext" href="https://github.com/tarantool/luajit/tree/skaplun/lj-1026-arm64-invalid-hrefk-offset-check">https://github.com/tarantool/luajit/tree/skaplun/lj-1026-arm64-invalid-hrefk-offset-check</a>
src/lj_asm_arm64.h | 2 +-
...-arm64-invalid-hrefk-offset-check.test.lua | 48 +++++++++++++++++++
2 files changed, 49 insertions(+), 1 deletion(-)
create mode 100644 test/tarantool-tests/lj-1026-arm64-invalid-hrefk-offset-check.test.lua
diff --git a/src/lj_asm_arm64.h b/src/lj_asm_arm64.h
index 6c7b011f..a7f059a2 100644
--- a/src/lj_asm_arm64.h
+++ b/src/lj_asm_arm64.h
@@ -885,7 +885,7 @@ static void asm_hrefk(ASMState *as, IRIns *ir)
IRIns *irkey = IR(kslot->op1);
int32_t ofs = (int32_t)(kslot->op2 * sizeof(Node));
int32_t kofs = ofs + (int32_t)offsetof(Node, key);
- int bigofs = !emit_checkofs(A64I_LDRx, ofs);
+ int bigofs = !emit_checkofs(A64I_LDRx, kofs);
Reg dest = (ra_used(ir) || bigofs) ? ra_dest(as, ir, RSET_GPR) : RID_NONE;
Reg node = ra_alloc1(as, ir->op1, RSET_GPR);
Reg key, idx = node;
diff --git a/test/tarantool-tests/lj-1026-arm64-invalid-hrefk-offset-check.test.lua b/test/tarantool-tests/lj-1026-arm64-invalid-hrefk-offset-check.test.lua
new file mode 100644
index 00000000..de243814
--- /dev/null
+++ b/test/tarantool-tests/lj-1026-arm64-invalid-hrefk-offset-check.test.lua
@@ -0,0 +1,48 @@
+local tap = require('tap')
+
+-- Test file to demonstrate LuaJIT misbehaviour when assembling
+-- HREFK instruction on arm64 with the huge offset.
+-- See also: <a class="moz-txt-link-freetext" href="https://github.com/LuaJIT/LuaJIT/issues/1026">https://github.com/LuaJIT/LuaJIT/issues/1026</a>.
+local test = tap.test('lj-1026-arm64-invalid-hrefk-offset-check'):skipcond({
+ ['Test requires JIT enabled'] = not jit.status(),</pre>
</blockquote>
It is an ARM-specific patch, should we add a condition for ARM here?<br>
<blockquote type="cite"
cite="mid:20250612093651.7552-1-skaplun@tarantool.org">
<pre wrap="" class="moz-quote-pre">
+})
+
+test:plan(1)
+
+-- The assertion fails since in HREFK we are checking the offset
+-- from the hslots of the table of the Node structure itself</pre>
</blockquote>
s/Node/`Node`/<br>
<blockquote type="cite"
cite="mid:20250612093651.7552-1-skaplun@tarantool.org">
<pre wrap="" class="moz-quote-pre">
+-- instead of its inner field `key` (with additional 8 bytes).
+-- So to test this, we generate a big table with constant keys
+-- and compile a trace for each HREFK possible.
+
+local big_tab = {}
+-- The map of the characters to generate constant string keys.
+-- The offset of the node should be 4096 * 8. It takes at least
+-- 1365 keys to hit this value. The maximum possible slots in the
+-- hash part is 2048, so to fill it with the maximum density (with
+-- the way below), we need 45 * 45 = 2025 keys.
+local chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRS'
+for c1 in <a class="moz-txt-link-freetext" href="chars:gmatch('.')">chars:gmatch('.')</a> do
+ for c2 in <a class="moz-txt-link-freetext" href="chars:gmatch('.')">chars:gmatch('.')</a> do
+ big_tab[c1 .. c2] = 1
+ end
+end
+
+jit.opt.start('hotloop=1')
+
+-- Generate bunch of traces.
+for c1 in <a class="moz-txt-link-freetext" href="chars:gmatch('.')">chars:gmatch('.')</a> do
+ for c2 in <a class="moz-txt-link-freetext" href="chars:gmatch('.')">chars:gmatch('.')</a> do
+ loadstring([=[
+ local t = ...
+ for i = 1, 4 do
+ -- HREFK generation.
+ t[ ']=] .. c1 .. c2 .. [=[' ] = i
+ end
+ ]=])(big_tab)
+ end
+end
+
+test:ok(true, 'no assertion failed')</pre>
</blockquote>
<p>I would replace testcase description to something like "emitted
assembly is correct".</p>
<p>Feel free to ignore.<br>
</p>
<blockquote type="cite"
cite="mid:20250612093651.7552-1-skaplun@tarantool.org">
<pre wrap="" class="moz-quote-pre">
+
+test:done(true)
</pre>
</blockquote>
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