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Re: [PATCH] gdb/arm-tdep.c: Remove "Infinite loop detected" error message.
- From: Pedro Alves <palves at redhat dot com>
- To: Richard Earnshaw <rearnsha at arm dot com>
- Cc: Will Newton <will dot newton at linaro dot org>, "gdb-patches at sourceware dot org" <gdb-patches at sourceware dot org>, Patch Tracking <patches at linaro dot org>
- Date: Tue, 19 Nov 2013 16:30:06 +0000
- Subject: Re: [PATCH] gdb/arm-tdep.c: Remove "Infinite loop detected" error message.
- Authentication-results: sourceware.org; auth=none
- References: <527D12A4 dot 6070109 at linaro dot org> <528B7E63 dot 90208 at arm dot com>
On 11/19/2013 03:06 PM, Richard Earnshaw wrote:
> On 08/11/13 16:34, Will Newton wrote:
>> Since as far back as the beginning of the sourceware repository
>> the ARM port has printed an error "Infinite loop detected" when
>> the next_pc calculated is the same as the current one, for example
>> when encountering a branch to the current PC address.
>> This causes the test gdb.base/random-signal.exp as the error message
>> is not expected. I have not been able to find a good reason for the
>> message to be here so remove it and let the test pass.
>> 2013-11-08 Will Newton <firstname.lastname@example.org>
>> * arm-tdep.c (arm_get_next_pc): Remove "Infinite loop detected"
>> error message.
> I guess the reasoning for this is that you can't single-step a
> 'branch-to-self' instruction, since the next instruction (where the new
> breakpoint has to go) is the same as the current instruction.
You should. It should stop again in the same place.
> However, it ought to be the higher levels of GDB that handle this, not
> some random low-level function like get-next-pc.
I just tried it on x86-64 (on a gdb branch that makes x86 use
software single-step), and it works as expected:
Dump of assembler code for function main:
0x000000000040049c <+0>: push %rbp
0x000000000040049d <+1>: mov %rsp,%rbp
=> 0x00000000004004a0 <+4>: jmp 0x4004a0 <main+4>
0x00000000004004a2 <+6>: pop %rbp
0x00000000004004a3 <+7>: retq
End of assembler dump.
6 asm ("here: jmp here");
(gdb) set debug infrun 1
infrun: clear_proceed_status_thread (process 29432)
infrun: proceed (addr=0xffffffffffffffff, signal=GDB_SIGNAL_DEFAULT, step=1)
infrun: resume (step=1, signal=GDB_SIGNAL_0), trap_expected=0, current thread [process 29432] at 0x4004a0
next pc: 0x4004a0 ==> 0x4004a0
infrun: inserting single-step breakpoint at 0x4004a0
infrun: wait_for_inferior ()
infrun: target_wait (-1, status) =
infrun: 29432 [process 29432],
infrun: status->kind = stopped, signal = GDB_SIGNAL_TRAP
infrun: stop_pc = 0x4004a0
6 asm ("here: jmp here");