Comment 12 for bug 757702

I see 0x00000008 ().

I am using qemu-0.14.0.tar.gz available for QEMU Downloads.

--Anup

On Tue, Apr 12, 2011 at 5:12 PM, Peter Maydell <email address hidden>wrote:

> > Also, in the test case hits 0x8 after encountering UNDEF instruction
> at 0x100058.
>
> So if you run qemu like this:
> qemu-system-arm -M realview-pb-a8 -serial stdio -kernel arm_test.elf -s -S
>
> and run arm-none-gnueabi-gdb with no arguments and in gdb type these
> commands:
>
> (gdb) target remote :1234
> Remote debugging using :1234
> 0x00100000 in ?? ()
> (gdb) break *0x4
> Breakpoint 1 at 0x4
> (gdb) break *0x8
> Breakpoint 2 at 0x8
> (gdb) c
> Continuing.
>
> ...what does gdb do?
> (For me it says "Breakpoint 1, 0x00000004 in ?? ()" which is what I
> expect.)
>
> --
> You received this bug notification because you are a direct subscriber
> of the bug.
> https://bugs.launchpad.net/bugs/757702
>
> Title:
> Undefined instruction exception starts at offset 0x8 instead of 0x4
>
> Status in QEMU:
> New
>
> Bug description:
> ARMv7a has lot of undefined instruction from its instruction opcode
> space. This undefined instructions are very useful for replacing
> sensitive non-priviledged instructions of guest operating systems
> (virtualization). The undefined instruction exception executes at
> <exception_base> + 0x4, where <exception_base> can be 0x0 or
> 0xfff00000. Currently, in qemu 0.14.0 undefined instruction fault at
> 0x8 offset instead of 0x4. This was not a problem with qemu 0.13.0,
> seems like this is a new bug. As as example, if we try to execute
> value "0xec019800" in qemu 0.14.0 then it should cause undefined
> exception at <exception_base>+0x4 since "0xec019800" is an undefined
> instruction.
>
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>