I would suggest you use the builtin simulator and its debugger. See
https://code.google.com/p/v8-wiki/wiki/ARMDebuggingWithTheSimulator
if you have gdb 7 or later, you can also try to build with gdbjit support
('gdbjit=on' on the make command and '--gdbjit' on the d8 command).
Rodolph.
On Thu, 9 Apr 2015 at 10:29 Ben Noordhuis <[email protected]> wrote:
> On Thu, Apr 9, 2015 at 6:32 AM, Wilson Lian <[email protected]> wrote:
> > Sorry if this is the wrong list. If there's a more appropriate one,
> please
> > let me know.
> >
> > I've built a debug release of V8 (at git revision 1398078) for ARMv7, and
> > I'm trying to set GDB breakpoints in JIT-generated code. However when I
> do,
> > various crashes abound. Setting a breakpoint at the first instruction of
> an
> > unoptimized function results in a segfault, and doing the same thing in
> an
> > optimized function produces a sigabort due to a false assertion in the
> > deoptimizer.
> >
> > Are others encountering this? Is there a workaround or maybe another
> > debugger that doesn't have these problems?
> >
> > What follows is a breakdown of how I reproduce the crashes:
> > First, the unoptimized code case. I start the d8 shell in gdb and
> declare
> > and invoke a function, noting the address of the emitted code thanks to
> the
> > --print-code flag. I set a gdb breakpoint at that address, continue, then
> > invoke the same function again. Here, I would expect execution to pause
> at
> > the first instruction of the declared function, but instead I get a
> > segfault.
> > $ gdb --args out/arm.debug/d8 --print-code
> >
> > GNU gdb (GDB) 7.4.1-debian
> > ...
> >
> > (gdb) r
> > ...
> >
> > d8> function foo(x) {return x ^ 0x1234;}
> > ...
> > d8> foo(0);
> > ...
> >
> > --- Code ---
> > source_position = 12
> > kind = FUNCTION
> > name = foo
> > Instructions (size = 196)
> > 0x2df888e0 0 e59d2004 ldr r2, [sp, #+4]
> > 0x2df888e4 4 e59ac014 ldr ip, [r10, #+20]
> > ...
> > (gdb) br *0x2df888e0
> > Breakpoint 1 at 0x2df888e0
> >
> > (gdb) c
> > d8> foo(1);
> > ...
> >
> > Program received signal SIGSEGV, Segmentation fault.
> > 0x2df888fc in ?? ()
> >
> > (gdb) bt
> > #0 0x2df888fc in ?? ()
> >
> >
> > For the optimized code, my method is mostly the same, but the crash is
> > different. I start the d8 shell with --always opt to force optimized
> code
> > generation. After setting the breakpoint and invoking my JS function
> again,
> > there is an invalid assertion in the deoptimizer that crashes the
> process.
> >
> > $ gdb --args out/arm.debug/d8 --print-code --always-opt
> >
> > GNU gdb (GDB) 7.4.1-debian
> > ...
> >
> > (gdb) r
> > ...
> >
> > d8> function foo(x) {return x ^ 0x1234;}
> > ...
> > d8> foo(0);
> > ...
> >
> > --- Optimized code ---
> > optimization_id = 21
> > source_position = 12
> > kind = OPTIMIZED_FUNCTION
> > name = foo
> > stack_slots = 1
> >
> > Instructions (size = 131)
> > 0x51f10720 0 e92d4882 stmdb sp!, {r1, r7, fp, lr}
> > 0x51f10724 4 e1a0c00c mov ip, ip...
> >
> > ...
> > (gdb) br * 0x51f10720
> > Breakpoint 1 at 0x2df888e0
> >
> > (gdb) c
> > d8> foo(1);
> > ...
> >
> > #
> > # Fatal error in ../src/deoptimizer.cc, line 2726
> > # CHECK_EQ(Smi::cast(function), Smi::FromInt(StackFrame::STUB)) failed
> > # Expected: 0x2
> > # Found: 0xc
> > #
> >
> > ==== C stack trace ===============================
> >
> > (empty)
> >
> > Program received signal SIGABRT, Aborted.
> > 0xf75a7f96 in ?? () from /lib/arm-linux-gnueabihf/libc.so.6
> >
> > (gdb) bt
> > #0 0xf75a7f96 in ?? () from /lib/arm-linux-gnueabihf/libc.so.6
> > #1 0xf75b5f8a in raise () from /lib/arm-linux-gnueabihf/libc.so.6
> > #2 0xf75b8428 in abort () from /lib/arm-linux-gnueabihf/libc.so.6
> > #3 0x00b20aaa in v8::base::OS::Abort () at
> > ../src/base/platform/platform-posix.cc:220
> > #4 0x00b1d5ca in V8_Fatal (file=0xc89a2c "../src/deoptimizer.cc",
> > line=2726, format=0xc560d0 "CHECK_EQ(%s, %s) failed\n# Expected: %p\n#
> > Found: %p") at ../src/base/logging.cc:87
> > #5 0x005a8b60 in CheckEqualsHelper (file=0xc89a2c
> "../src/deoptimizer.cc",
> > line=2726, expected_source=0xc8b07c "Smi::cast(function)", expected=0x2,
> > value_source=0xc8b090 "Smi::FromInt(StackFrame::STUB)", value=0xc) at
> > .././src/base/logging.h:139
> > #6 0x006840be in v8::internal::Deoptimizer::ComputeIncomingArgumentSize
> > (this=0x19bd4d8, function=0x2) at ../src/deoptimizer.cc:2726
> > #7 0x0068405e in v8::internal::Deoptimizer::ComputeFixedSize
> > (this=0x19bd4d8, function=0x2) at ../src/deoptimizer.cc:2717
> > #8 0x00683fbc in v8::internal::Deoptimizer::ComputeInputFrameSize
> > (this=0x19bd4d8) at ../src/deoptimizer.cc:2700
> > #9 0x0067e91a in v8::internal::Deoptimizer::Deoptimizer
> (this=0x19bd4d8,
> > isolate=0x1995688, function=0x0, type=v8::internal::Deoptimizer::EAGER,
> > bailout_id=1, from=0x51f10790 "\001", fp_to_sp_delta=12,
> optimized_code=0x0)
> > at ../src/deoptimizer.cc:612
> > #10 0x0067d32e in v8::internal::Deoptimizer::New (function=0x2,
> > type=v8::internal::Deoptimizer::EAGER, bailout_id=1, from=0x51f10790
> "\001",
> > fp_to_sp_delta=12, isolate=0x1995688) at ../src/deoptimizer.cc:90
> > #11 0x5fb0a268 in ?? ()
> > #12 0x5fb0a268 in ?? ()
> >
> > Backtrace stopped: previous frame identical to this frame (corrupt
> stack?)
>
> I speculate that you need to pass --noconcurrent_osr
> --noconcurrent_recompilation --noconcurrent_sweeping on the command
> line.
>
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