From: Tom Tromey <tom@tromey.com>
To: Simon Farre via Gdb-patches <gdb-patches@sourceware.org>
Cc: Simon Farre <simon.farre.cx@gmail.com>
Subject: Re: [PATCH v1] gdb/DAP Fix disassemble bug
Date: Mon, 26 Jun 2023 12:34:02 -0600 [thread overview]
Message-ID: <87cz1ixecl.fsf@tromey.com> (raw)
In-Reply-To: <20230626161654.207687-1-simon.farre.cx@gmail.com> (Simon Farre via Gdb-patches's message of "Mon, 26 Jun 2023 18:16:54 +0200")
>>>>> "Simon" == Simon Farre via Gdb-patches <gdb-patches@sourceware.org> writes:
Simon> Fixes disassembleRequest
Simon> The field instructionOffset can be negative. Previous patch made it so
Simon> that sometimes the request got calculated to 0 instructions, when it
Simon> meant to retrieve disasm for -50 to 0 (current position).
I don't think this will work correctly, because this isn't counting by
instruction but rather by byte.
instructionOffset is defined in terms of instructions:
Offset (in instructions) to be applied after the byte offset (if any)
before disassembling. Can be negative.
I must have missed the "negative" note, or maybe I just ignored it
without documenting that -- since I wonder how it can possibly work. it
seems to me that on architectures with variable length instructions, you
can't really disassemble in "reverse" like that.
I guess one idea would be to back up to the previous symbol and start
disassembling from there. I feel like the TUI did this, though, and ran
into all kinds of weird corner cases.
Simon> - for elt in arch.disassemble(pc, count=total_count)[skip_insns:]:
I notice now that the current code also neglects this part of the spec:
* An adapter must return exactly this number of instructions - any
* unavailable instructions should be replaced with an implementation-defined
* 'invalid instruction' value.
Tom
next prev parent reply other threads:[~2023-06-26 18:34 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-26 16:16 Simon Farre
2023-06-26 18:34 ` Tom Tromey [this message]
2023-06-26 22:00 ` Simon Farre
2023-06-26 22:11 ` Simon Farre
2023-06-27 15:32 ` Simon Farre
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