Hi Alex,
September 21, 2025 at 6:46 PM, "Alex Bennée" <[email protected]
mailto:[email protected]?to=%22Alex%20Benn%C3%A9e%22%20%3Calex.bennee%40linaro.org%3E
> wrote:
> Julian Ganz <[email protected]> writes:
> > +static void report_mismatch(const char *pc_name, unsigned int vcpu_index,
> > + enum qemu_plugin_discon_type type, uint64_t last,
> > + uint64_t expected, uint64_t encountered)
> > +{
> > + GString *report;
> >
> This could be:
>
> g_autoptr(GString) buf = g_string_new(NULL);
I wanted to avoid doing an allocation regardless of whether we do have
anything to report or not. But I guess a performance plugin isn't
performance critical enough to worry? Anyway, I will have another look
at g_autoptr.
> > + const char *discon_type_name = "unknown";
> > +
> > + if (addr_eq(expected, encountered)) {
> > + return;
> > + }
> > +
> > + switch (type) {
> > + case QEMU_PLUGIN_DISCON_INTERRUPT:
> > + discon_type_name = "interrupt";
> > + break;
> > + case QEMU_PLUGIN_DISCON_EXCEPTION:
> > + discon_type_name = "exception";
> > + break;
> > + case QEMU_PLUGIN_DISCON_HOSTCALL:
> > + discon_type_name = "hostcall";
> > + break;
> > + default:
> > + break;
> > + }
> > +
> > + report = g_string_new(NULL);
> > + g_string_append_printf(report,
> > + "Discon %s PC mismatch on VCPU %d\nExpected: %"
> > + PRIx64"\nEncountered: %"PRIx64"\nExecuted Last: %"
> > + PRIx64"\nEvent type: %s\n",
> > + pc_name, vcpu_index, expected, encountered, last,
> > + discon_type_name);
> > + qemu_plugin_outs(report->str);
> >
> I think we might want to flush here because
Yes we do. I probably (incorrectly) assumed `qemu_plugin_outs` already
did that.
>
> >
> > + if (abort_on_mismatch) {
> > + g_abort();
> > + }
> >
> This is firing on:
>
> 🕙17:35:50 alex@draig:tests/tcg/i386-linux-user on review/tcg-discon-v6
> [$!?]
> ➜ make run-plugin-catch-syscalls-with-libdiscons.so V=1
> timeout -s KILL --foreground 120 env
> QEMU=/home/alex/lsrc/qemu.git/builds/sanitisers/qemu-i386
> /home/alex/lsrc/qemu.git/builds/sanitisers/qemu-i386 -plugin
> ../plugins/libdiscons.so -d plugin -D catch-syscalls-with-libdiscons.so.pout
> catch-syscalls > run-plugin-catch-syscalls-with-libdiscons.so.out
> Aborted
> make: *** [Makefile:226: run-plugin-catch-syscalls-with-libdiscons.so] Error
> 134
> 🕙17:35:52 alex@draig:tests/tcg/i386-linux-user on review/tcg-discon-v6
> [$!?] [🔴 USAGE]
> ✗
>
> although it never gets to the point of reporting what failed:
>
> Thread 1 "qemu-i386" hit Breakpoint 1, __GI_abort () at ./stdlib/abort.c:72
> warning: 72 ./stdlib/abort.c: No such file or directory
> (gdb) bt
> #0 __GI_abort () at ./stdlib/abort.c:72
> #1 0x00007ffff630874d in report_mismatch (pc_name=0x7ffff630a220 "target",
> vcpu_index=0, type=QEMU_PLUGIN_DISCON_EXCEPTION, last=134574955,
> expected=134574953,
> encountered=134574955) at ../../tests/tcg/plugins/discons.c:89
> #2 0x00007ffff6308c0d in insn_exec (vcpu_index=0, userdata=0x0) at
> ../../tests/tcg/plugins/discons.c:132
> #3 0x00007fffea431114 in code_gen_buffer ()
> #4 0x000055555577b0a6 in cpu_tb_exec (cpu=0x529000005200, itb=0x7fffea431000
> <code_gen_buffer+200659>, tb_exit=0x7ffff49c9530) at
> ../../accel/tcg/cpu-exec.c:438
> #5 0x000055555577c92f in cpu_loop_exec_tb (cpu=0x529000005200,
> tb=0x7fffea431000 <code_gen_buffer+200659>, pc=134574955,
> last_tb=0x7ffff49c9540, tb_exit=0x7ffff49c9530)
> at ../../accel/tcg/cpu-exec.c:871
> #6 0x000055555577d151 in cpu_exec_loop (cpu=0x529000005200,
> sc=0x7ffff483a740) at ../../accel/tcg/cpu-exec.c:981
> #7 0x000055555577d2fe in cpu_exec_setjmp (cpu=0x529000005200,
> sc=0x7ffff483a740) at ../../accel/tcg/cpu-exec.c:998
> #8 0x000055555577d4c8 in cpu_exec (cpu=0x529000005200) at
> ../../accel/tcg/cpu-exec.c:1024
> #9 0x00005555557bfc83 in cpu_loop (env=0x529000007dd0) at
> ../../linux-user/i386/cpu_loop.c:215
> #10 0x00005555558ee3e1 in main (argc=4, argv=0x7fffffffe688,
> envp=0x7fffffffe6b0) at ../../linux-user/main.c:1038
> (gdb) f 1
> #1 0x00007ffff630874d in report_mismatch (pc_name=0x7ffff630a220 "target",
> vcpu_index=0, type=QEMU_PLUGIN_DISCON_EXCEPTION, last=134574955,
> expected=134574953,
> encountered=134574955) at ../../tests/tcg/plugins/discons.c:89
> 89 g_abort();
> (gdb) p report
> $1 = (GString *) 0x50300002bf00
> (gdb) p report->Str
> There is no member named Str.
> (gdb) p report->str
> $2 = (gchar *) 0x51100001fbc0 "Discon target PC mismatch on VCPU
> 0\nExpected: 8057369\nEncountered: 805736b\nExecuted Last: 805736b\nEvent
> type: exception\n"
> (gdb)
>
> I think this is where it is going wrong:
>
> IN: _dl_early_allocate
> 0x0805736b: 89 c2 movl %eax, %edx
> 0x0805736d: 8d 1c 28 leal (%eax, %ebp), %ebx
> 0x08057370: 89 c8 movl %ecx, %eax
> 0x08057372: cd 80 int $0x80
Thanks! I'll have a closer look.
> >
> > + g_string_free(report, true);
> >
> so we could drop this... or..
As aborting is optional, we should free.
Regards,
Julian
