From: David Laight <david.laight.linux@gmail.com>
To: Alexandre Chartre <alexandre.chartre@oracle.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>,
linux-kernel@vger.kernel.org, mingo@kernel.org,
peterz@infradead.org
Subject: Re: [PATCH v4 00/28] objtool: Function validation tracing
Date: Mon, 17 Nov 2025 12:37:29 +0000 [thread overview]
Message-ID: <20251117123729.72ffa3e2@pumpkin> (raw)
In-Reply-To: <81693206-9002-4669-ab74-fda3d31c25bb@oracle.com>
On Mon, 17 Nov 2025 10:47:06 +0100
Alexandre Chartre <alexandre.chartre@oracle.com> wrote:
> On 11/17/25 10:42, David Laight wrote:
...
> > Although I think there ought to be some indication of the 31 NOP bytes
> > at the end of the middle alternative.
>
> I am now compacting the code by removing all trailing NOPs. I should probably
> improve that with printing the actual number of NOPs, for example NOP31 (or nop31)
That is the sort of thing I was thinking of.
Perhaps the actual opcodes on one line - eg: NOP5; NOP5; NOP5; NOP1
> > I'd also decode those callq as 'callq .+6' - not sure what other people think?
> > It is rather specific to that code.
>
> This is done by libopcodes. I will need to check if there is an option to display
> the branch distance instead of the branch target.
The 'problem' is that mostly you want the branch target - except when it is small.
Then you don't need both 'address' and 'symbol+offset', and it is quicker to find
the target by looking at the branch distance.
I'm not sure how you'd please everyone :-)
I'm sure one of the disassemblers ends up giving you the target address in a form
that isn't on the instruction line!
I've definitely counted opcode bytes to find the target.
David
next prev parent reply other threads:[~2025-11-17 12:37 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-13 16:48 [PATCH v4 00/28] objtool: Function validation tracing Alexandre Chartre
2025-11-13 16:48 ` [PATCH v4 01/28] objtool: Move disassembly functions to a separated file Alexandre Chartre
2025-11-13 16:48 ` [PATCH v4 02/28] objtool: Create disassembly context Alexandre Chartre
2025-11-13 16:48 ` [PATCH v4 03/28] objtool: Disassemble code with libopcodes instead of running objdump Alexandre Chartre
2025-11-13 16:48 ` [PATCH v4 04/28] tool build: Remove annoying newline in build output Alexandre Chartre
2025-11-13 16:48 ` [PATCH v4 05/28] objtool: Print symbol during disassembly Alexandre Chartre
2025-11-13 16:48 ` [PATCH v4 06/28] objtool: Store instruction disassembly result Alexandre Chartre
2025-11-13 16:48 ` [PATCH v4 07/28] objtool: Disassemble instruction on warning or backtrace Alexandre Chartre
2025-11-13 16:48 ` [PATCH v4 08/28] objtool: Extract code to validate instruction from the validate branch loop Alexandre Chartre
2025-11-13 16:48 ` [PATCH v4 09/28] objtool: Record symbol name max length Alexandre Chartre
2025-11-13 16:48 ` [PATCH v4 10/28] objtool: Add option to trace function validation Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 11/28] objtool: Trace instruction state changes during " Alexandre Chartre
2025-11-14 21:21 ` Josh Poimboeuf
2025-11-17 7:33 ` Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 12/28] objtool: Improve register reporting " Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 13/28] objtool: Identify the different types of alternatives Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 14/28] objtool: Improve tracing of alternative instructions Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 15/28] objtool: Do not validate IBT for .return_sites and .call_sites Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 16/28] objtool: Add the --disas=<function-pattern> action Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 17/28] objtool: Print headers for alternatives Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 18/28] objtool: Disassemble group alternatives Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 19/28] objtool: Print addresses with alternative instructions Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 20/28] objtool: Disassemble exception table alternatives Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 21/28] objtool: Disassemble jump " Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 22/28] objtool: Fix address references in alternatives Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 23/28] objtool: Provide access to feature and flags of group alternatives Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 24/28] objtool: Function to get the name of a CPU feature Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 25/28] objtool: Improve naming of group alternatives Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 26/28] objtool: Get the destination name of a PV call Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 27/28] objtool: Improve the disassembly of the pv_ops call Alexandre Chartre
2025-11-15 1:34 ` kernel test robot
2025-11-17 7:37 ` Alexandre Chartre
2025-11-13 16:49 ` [PATCH v4 28/28] objtool: Print single line for alternatives with one instruction Alexandre Chartre
2025-11-13 19:55 ` [PATCH v4 00/28] objtool: Function validation tracing David Laight
2025-11-14 8:53 ` Alexandre Chartre
2025-11-14 1:48 ` Josh Poimboeuf
2025-11-14 9:56 ` Alexandre Chartre
2025-11-14 21:34 ` Josh Poimboeuf
2025-11-17 7:50 ` Alexandre Chartre
2025-11-17 9:42 ` David Laight
2025-11-17 9:47 ` Alexandre Chartre
2025-11-17 12:37 ` David Laight [this message]
2025-11-17 13:11 ` Alexandre Chartre
2025-11-17 22:09 ` David Laight
2025-11-17 22:38 ` Josh Poimboeuf
2025-11-18 9:58 ` David Laight
2025-11-18 7:19 ` Alexandre Chartre
2025-11-18 9:12 ` Peter Zijlstra
2025-11-18 11:39 ` Alexandre Chartre
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