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runtime: 0.381
instruction: 0.310
syscall: 0.309
qemu-arm (user mode) segfaults in uclibc-ng chroot after upgrade to 2.11.x
I use a qemu-user chroot + binfmt to build software targetting a raspberry pi. After upgrading from qemu-2.10.1 to 2.11.1 (Gentoo host), I noticed that on my uclibc-ng chroot qemu-arm will segfault when running python and importing the portage module.
I have bisected qemu down to this commit:
https://github.com/qemu/qemu/commit/18e80c55bb6ec17c05ec0ba717ec83933c2bfc07
If I recompile and change MAX_RESERVED_VA (from the above commit) back to 0x77000000 the problem goes away. NB I have no idea what that does, I just thought I'd see.
Other arm chroots (glibc, musl) do not segfault with qemu-2.11, only the uclibc-ng one. Not sure why.
The following backtrace was generated from running qemu-arm in gdb and recreating the segfault:
(gdb) where
#0 0x0000000060726046 in static_code_gen_buffer ()
#1 0x0000000060048789 in cpu_tb_exec (cpu=0x6278e310,
itb=0x60725f80 <static_code_gen_buffer+314624>)
at /usr/src/debug/app-emulation/qemu-2.11.1-r2/qemu-2.11.1/accel/tcg/cpu-exec.c:167
#2 0x000000006004937f in cpu_loop_exec_tb (cpu=0x6278e310,
tb=0x60725f80 <static_code_gen_buffer+314624>, last_tb=0x7fffffffd138,
tb_exit=0x7fffffffd130)
at /usr/src/debug/app-emulation/qemu-2.11.1-r2/qemu-2.11.1/accel/tcg/cpu-exec.c:627
#3 0x0000000060049600 in cpu_exec (cpu=0x6278e310)
at /usr/src/debug/app-emulation/qemu-2.11.1-r2/qemu-2.11.1/accel/tcg/cpu-exec.c:736
#4 0x00000000600511c3 in cpu_loop (env=0x627965b0)
at /usr/src/debug/app-emulation/qemu-2.11.1-r2/qemu-2.11.1/linux-user/main.c:585
#5 0x00000000600534eb in main (argc=4, argv=0x7fffffffd9b8,
envp=0x7fffffffd9e0)
at /usr/src/debug/app-emulation/qemu-2.11.1-r2/qemu-2.11.1/linux-user/main.c:4882
(gdb) info reg
rax 0x627965b0 1652123056
rbx 0x62717870 1651603568
rcx 0x606da000 1617797120
rdx 0x60726000 1618108416
rsi 0x60726000 1618108416
rdi 0x627965b0 1652123056
rbp 0x7fffffffd0c0 0x7fffffffd0c0
rsp 0x7fffffffd080 0x7fffffffd080
r8 0x0 0
r9 0x2 2
r10 0x0 0
r11 0x629280a0 1653768352
r12 0x60260e40 1613106752
r13 0x0 0
r14 0x606a5018 1617580056
r15 0x0 0
rip 0x60048789 0x60048789 <cpu_tb_exec+266>
eflags 0x10282 [ SF IF RF ]
cs 0x33 51
ss 0x2b 43
ds 0x0 0
es 0x0 0
fs 0x0 0
gs 0x0 0
(gdb)
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