Subject: [3.0.0] Segfault while building on ARMv7

From: Ludovic Courtès <[email-masked]>
Date: Mon, 20 Jan 2020 17:33:48 +0100

Hello,

Building 3.0.0 with Guix on ARMv7 reproducibly fails:

--8<---------------cut here---------------start------------->8---
  BOOTSTRAP GUILEC language/cps/loop-instrumentation.go
wrote `language/cps/loop-instrumentation.go'
  BOOTSTRAP GUILEC language/cps/peel-loops.go
wrote `language/cps/effects-analysis.go'
  BOOTSTRAP GUILEC language/cps/prune-top-level-scopes.go
wrote `language/cps/licm.go'
  BOOTSTRAP GUILEC language/cps/reify-primitives.go
wrote `language/cps/prune-top-level-scopes.go'
  BOOTSTRAP GUILEC language/cps/renumber.go
wrote `language/cps/peel-loops.go'
  BOOTSTRAP GUILEC language/cps/rotate-loops.go
wrote `language/cps/reify-primitives.go'
  BOOTSTRAP GUILEC language/cps/optimize.go
wrote `language/cps/renumber.go'
  BOOTSTRAP GUILEC language/cps/simplify.go
wrote `language/cps/rotate-loops.go'
  BOOTSTRAP GUILEC language/cps/self-references.go
wrote `language/cps/optimize.go'
  BOOTSTRAP GUILEC language/cps/slot-allocation.go
wrote `language/cps/self-references.go'
  BOOTSTRAP GUILEC language/cps/spec.go
wrote `language/cps/simplify.go'
  BOOTSTRAP GUILEC language/cps/specialize-primcalls.go
wrote `language/cps/spec.go'
  BOOTSTRAP GUILEC language/cps/specialize-numbers.go
/gnu/store/nvkn00kq4x4g5wjjjvjj6rhzs0ihihxl-bash-minimal-5.0.7/bin/bash: line 6: 23019 Segmentation fault      (core dumped) GUILE_AUTO_COMPILE=0 ../meta/build-env guild compile --target="arm-unknown-linux-gnueabihf" -O1 -Oresolve-primitives -L "/tmp/guix-build-guile-next-3.0.0.drv-0/guile-3.0.0/module" -L "/tmp/guix-build-guile-next-3.0.0.drv-0/guile-3.0.0/guile-readline" -o "language/cps/specialize-primcalls.go" "../module/language/cps/specialize-primcalls.scm"
make[2]: *** [Makefile:1931: language/cps/specialize-primcalls.go] Error 139
make[2]: *** Waiting for unfinished jobs....
wrote `language/cps/slot-allocation.go'
wrote `language/cps/specialize-numbers.go'
make[2]: Leaving directory '/tmp/guix-build-guile-next-3.0.0.drv-0/guile-3.0.0/bootstrap'
make[1]: *** [Makefile:1849: all-recursive] Error 1
--8<---------------cut here---------------end--------------->8---

It seems to always happen while building ‘specialize-primcalls.go’.

(See
<https://ci.guix.gnu.org/log/8b8c0hxvm9qa5kff168vdr3943cc2s61-guile-next-3.0.0>.)

The backtrace is unfortunately not all that readable:

--8<---------------cut here---------------start------------->8---
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0xf5c67b74 in ?? ()
[Current thread is 1 (Thread 0xf7fe8010 (LWP 23019))]
(gdb) bt
#0  0xf5c67b74 in ?? ()
#1  0xf7f3ffcc in scm_jit_enter_mcode (thread=0xdedc20,
    mcode=0xf5c67a00 " 8\r\032(-@\360c\203%i\250B\300\362_\203\240`\245m") at jit.c:5725
#2  0xf7093a40 in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb) info threads
  Id   Target Id                     Frame
* 1    Thread 0xf7fe8010 (LWP 23019) 0xf5c67b74 in ?? ()
  2    Thread 0xf7894460 (LWP 23042) 0xf7e8f034 in __libc_do_syscall ()
   from /gnu/store/n7c20pjm6q1xq1gqjqzzys1yk9fy7n1k-glibc-2.29/lib/libpthread.so.0
  3    Thread 0xf69a5460 (LWP 23045) 0xf7e8f034 in __libc_do_syscall ()
   from /gnu/store/n7c20pjm6q1xq1gqjqzzys1yk9fy7n1k-glibc-2.29/lib/libpthread.so.0
(gdb) frame 0
#0  0xf5c67b74 in ?? ()
(gdb) disassemble 0xf5c67a00,+500
Dump of assembler code from 0xf5c67a00 to 0xf5c67bf4:
   0xf5c67a00:  subs    r0, #32
   0xf5c67a02:  subs    r5, r1, r0
   0xf5c67a04:  cmp     r5, #40 ; 0x28
   0xf5c67a06:  bne.w   0xf5c680d0
   0xf5c67a0a:  ldr     r5, [r4, #16]
   0xf5c67a0c:  cmp     r0, r5
   0xf5c67a0e:  blt.w   0xf5c680d0
   0xf5c67a12:  str     r0, [r4, #8]
   0xf5c67a14:  ldr     r5, [r4, #88]   ; 0x58
   0xf5c67a16:  cmp     r5, #0
   0xf5c67a18:  beq.w   0xf5c68102
   0xf5c67a1c:  ldrt    r6, [r5]
   0xf5c67a20:  str     r6, [r4, #88]   ; 0x58
   0xf5c67a22:  str     r5, [r0, #24]
   0xf5c67a24:  movw    r5, #1293       ; 0x50d
   0xf5c67a28:  movs    r6, #0
   0xf5c67a2a:  str     r5, [r0, #16]
   0xf5c67a2c:  str     r6, [r0, #20]
   0xf5c67a2e:  ldr     r5, [r0, #24]
   0xf5c67a30:  ldr     r6, [r0, #16]
   0xf5c67a32:  str     r6, [r5, #0]
   0xf5c67a34:  ldr     r5, [r0, #32]
   0xf5c67a36:  ldr     r5, [r5, #4]
   0xf5c67a38:  str     r5, [r0, #16]
[…]
   0xf5c67b5e:  cmp     r5, #0
   0xf5c67b60:  ble.w   0xf5c67fce
   0xf5c67b64:  ldr     r5, [r0, #32]
   0xf5c67b66:  ldr     r5, [r5, #20]
   0xf5c67b68:  str     r5, [r0, #16]
   0xf5c67b6a:  ldr     r5, [r0, #16]
   0xf5c67b6c:  ldr     r5, [r5, #4]
   0xf5c67b6e:  str     r5, [r0, #16]
   0xf5c67b70:  mov.w   r12, #0
=> 0xf5c67b74:  ldrt    r5, [r12]
   0xf5c67b78:  str     r5, [r0, #8]
   0xf5c67b7a:  ldr     r5, [r0, #8]
   0xf5c67b7c:  ldr     r6, [r0, #16]
   0xf5c67b7e:  cmp     r5, r6
   0xf5c67b80:  bne.w   0xf5c67f80
[…]
(gdb) info registers
r0             0xf7093a20          4144577056
r1             0xf7093a48          4144577096
r2             0x0                 0
r3             0xf7a24001          4154605569
r4             0x74e00             478720
r5             0xdedc20            14605344
r6             0x0                 0
r7             0xf5c67a00          4123425280
r8             0x0                 0
r9             0x0                 0
r10            0xf7fc4bdc          4160506844
r11            0xf7fb5000          4160442368
r12            0x0                 0
sp             0xfffedc50          0xfffedc50
lr             0xf7f3ffcd          -135004211
pc             0xf5c67b74          0xf5c67b74
cpsr           0x200f0030          537854000
fpscr          0x60000000          1610612736
(gdb) frame 1
#1  0xf7f3ffcc in scm_jit_enter_mcode (thread=0xdedc20, 
    mcode=0xf5c67a00 " 8\r\032(-@\360c\203%i\250B\300\362_\203\240`\245m") at jit.c:5725
5725      enter_mcode (thread, mcode);
(gdb) info locals
No locals.
(gdb) p *thread
$2 = {next_thread = 0x5, vm = {ip = 0xdecd50, sp = 0x324602ae, fp = 0xdebc50, stack_limit = 0x30d, 
    compare_result = 72 'H', apply_hook_enabled = 130 '\202', return_hook_enabled = 82 'R', 
    next_hook_enabled = 1 '\001', abort_hook_enabled = 192 '\300', disable_mcode = 159 '\237', engine = 166 '\246', 
    unused = 1 '\001', stack_size = 15218, stack_bottom = 0x20d, apply_hook = 0x1528240, return_hook = 0x1a69fc0, 
    next_hook = 0x0, abort_hook = 0x5, stack_top = 0xdecd68, overflow_handler_stack = 0x28f45b3e, 
    registers = 0xdebc58, mra_after_abort = 0x20045 "", trace_level = -140048256}, pending_asyncs = 0x116ab78, 
  block_asyncs = 22184512, freelists = {0x20045, 0xf7a707ec, 0x1162bf8, 0x1528248, 0x5, 0x248360, 0x30999e00, 
    0xdebc60, 0x20d, 0x1528250, 0x1a69fc0, 0x0, 0x20045, 0xf7a70880, 0x1167440, 0x1528250, 0x5, 0xdecd80, 0x181aface, 
    0xdebc68, 0x20d, 0x1528258, 0x1a69fc0, 0x0, 0x20045, 0xf7a70880, 0x1167460, 0x1528258, 0x5, 0x248370, 0x91c2f1f, 
    0xdebc70}, pointerless_freelists = {0x30d, 0x7f1720, 0x1a69fc0, 0x1496, 0x30d, 0xdedd50, 0x96, 0x16, 0x5, 
    0x789740, 0x3275b29e, 0xdebc78, 0x30d, 0xdedd50, 0x16, 0x3fffffe, 0x30d, 0xdedd50, 0x96, 0x3fe, 0x5, 0xdecd98, 
    0x3afba8fc, 0xdebc80, 0x30d, 0x7f1720, 0x96, 0x16, 0x20d, 0x1528260, 0x1a69fc0, 0x0}, handle = 0x5, 
  pthread = 14601648, result = 0x38a97220, exited = 14597256, guile_mode = 131141, needs_unregister = -140048256, 
  wake = 0x1162128, sleep_cond = {__data = {{__wseq = 95281925316411917, __wseq32 = {__low = 525, 
          __high = 22184552}}, {__g1_start = 27697088, __g1_start32 = {__low = 27697088, __high = 0}}, __g_refs = {5, 
        7903072}, __g_size = {67881032, 14597264}, __g1_orig_size = 131141, __wrefs = 4154919040, __g_signals = {
        18228776, 22184552}}, 
    __size = "\r\002\000\000h\202R\001\300\237\246\001\000\000\000\000\005\000\000\000`\227x\000H\310\v\004\220\274\336\000E\000\002\000\200\b\247\367(&\026\001h\202R\001", __align = 95281925316411917}, sleep_pipe = {525, 22184560}, 
  dynamic_state = 0xa, dynstack = {base = 0x0, top = 0x5, limit = 0x789780}, continuation_root = 0x2db7da0c, 
  continuation_base = 0xdebc98, base = 0x20d, jit_state = 0xdede20}
--8<---------------cut here---------------end--------------->8---

Unfortunately I’m unable to reproduce the bug outside Guix’s build
environment, even with ASLR disabled (what guix-daemon does).

I wonder if that could be the same issue as
<https://issues.guix.gnu.org/issue/39118>.

I’ll happily take suggestions as to what debug info would be useful and
what I could bisect!

Ludo’.