The problem is that we're now generating many more temporaries
than before, and running out of the statically allocated amount.
Changing a debug assert to a full assert will change the SEGV
into an ABRT.  :-)

diff --git a/tcg/tcg.c b/tcg/tcg.c
index 8f8badb61c..c376afe56a 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -1207,7 +1207,7 @@ void tcg_func_start(TCGContext *s)
 static inline TCGTemp *tcg_temp_alloc(TCGContext *s)
 {
     int n = s->nb_temps++;
-    tcg_debug_assert(n < TCG_MAX_TEMPS);
+    g_assert(n < TCG_MAX_TEMPS);
     return memset(&s->temps[n], 0, sizeof(TCGTemp));
 }
 

The problem can be worked around temporarily by increasing the
number of temporaries:

diff --git a/include/tcg/tcg.h b/include/tcg/tcg.h
index 504c5e9bb0..8fe32bb03c 100644
--- a/include/tcg/tcg.h
+++ b/include/tcg/tcg.h
@@ -275,7 +275,7 @@ typedef struct TCGPool {
 
 #define TCG_POOL_CHUNK_SIZE 32768
 
-#define TCG_MAX_TEMPS 512
+#define TCG_MAX_TEMPS 2048
 #define TCG_MAX_INSNS 512
 
 /* when the size of the arguments of a called function is smaller than


But a proper solution is to dynamically allocate the temps.

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1912065

Title:
  Segfaults in tcg/optimize.c:212 after commit
  7c79721606be11b5bc556449e5bcbc331ef6867d

Status in QEMU:
  In Progress

Bug description:
  QEMU segfaults to NULL dereference in tcg/optimize.c:212 semi-randomly
  after commit 7c79721606be11b5bc556449e5bcbc331ef6867d

  Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
  Exception Codes:       KERN_INVALID_ADDRESS at 0x0000000000000020
  Exception Note:        EXC_CORPSE_NOTIFY

  ...

  Thread 4 Crashed:
  0   qemu-system-ppc               	0x0000000109cd26d2 tcg_opt_gen_mov + 178 (optimize.c:212)
  1   qemu-system-ppc               	0x0000000109ccf838 tcg_optimize + 5656
  2   qemu-system-ppc               	0x0000000109c27600 tcg_gen_code + 64 (tcg.c:4490)
  3   qemu-system-ppc               	0x0000000109c17b6d tb_gen_code + 493 (translate-all.c:1952)
  4   qemu-system-ppc               	0x0000000109c16085 tb_find + 41 (cpu-exec.c:454) [inlined]
  5   qemu-system-ppc               	0x0000000109c16085 cpu_exec + 2117 (cpu-exec.c:810)
  6   qemu-system-ppc               	0x0000000109c09ac3 tcg_cpus_exec + 35 (tcg-cpus.c:57)
  7   qemu-system-ppc               	0x0000000109c75edd rr_cpu_thread_fn + 445 (tcg-cpus-rr.c:217)
  8   qemu-system-ppc               	0x0000000109e41fae qemu_thread_start + 126 (qemu-thread-posix.c:521)
  9   libsystem_pthread.dylib       	0x00007fff2038e950 _pthread_start + 224
  10  libsystem_pthread.dylib       	0x00007fff2038a47b thread_start + 15

  Here the crash is in tcg/optimize.c line 212:

    mask = si->mask;

  "si" is NULL. The NULL value arises from tcg/optimize.c line 198:

   si = ts_info(src_ts);

  I did not attempt to determine the root cause of this issue, however.
  It clearly is related to the "tcg/optimize" changes in this commit.
  The previous commit c0dd6654f207810b16a75b673258f5ce2ceffbf0 doesn't
  crash.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1912065/+subscriptions

Patchew URL: https://patchew.org/QEMU/161099084144.30067.897245088295398204.malone@chaenomeles.canonical.com/



Hi,

This series seems to have some coding style problems. See output below for
more information:

Type: series
Message-id: 161099084144.30067.897245088295398204.malone@chaenomeles.canonical.com
Subject: [Bug 1912065] Re: Segfaults in tcg/optimize.c:212 after commit 7c79721606be11b5bc556449e5bcbc331ef6867d

=== TEST SCRIPT BEGIN ===
#!/bin/bash
git rev-parse base > /dev/null || exit 0
git config --local diff.renamelimit 0
git config --local diff.renames True
git config --local diff.algorithm histogram
./scripts/checkpatch.pl --mailback base..
=== TEST SCRIPT END ===

Updating 3c8cf5a9c21ff8782164d1def7f44bd888713384
From https://github.com/patchew-project/qemu
 * [new tag]         patchew/161099084144.30067.897245088295398204.malone@chaenomeles.canonical.com -> patchew/161099084144.30067.897245088295398204.malone@chaenomeles.canonical.com
 - [tag update]      patchew/cover.1610638428.git.jag.raman@oracle.com -> patchew/cover.1610638428.git.jag.raman@oracle.com
Switched to a new branch 'test'
0b7840a Segfaults in tcg/optimize.c:212 after commit 7c79721606be11b5bc556449e5bcbc331ef6867d

=== OUTPUT BEGIN ===
ERROR: Missing Signed-off-by: line(s)

total: 1 errors, 0 warnings, 16 lines checked

Commit 0b7840aec0d8 (Segfaults in tcg/optimize.c:212 after commit 7c79721606be11b5bc556449e5bcbc331ef6867d) has style problems, please review.  If any of these errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.
=== OUTPUT END ===

Test command exited with code: 1


The full log is available at
http://patchew.org/logs/161099084144.30067.897245088295398204.malone@chaenomeles.canonical.com/testing.checkpatch/?type=message.
---
Email generated automatically by Patchew [https://patchew.org/].
Please send your feedback to patchew-devel@redhat.com

On 1/18/21 8:00 AM, no-reply@patchew.org wrote:
> Patchew URL: https://patchew.org/QEMU/161099084144.30067.897245088295398204.malone@chaenomeles.canonical.com/

Can we get patchew to not respond to launchpad threads?


r~