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Message-ID: <CAN2=dsz8tob_c+nJBJnzC_dvF8J1nre5cbmL+nYERRbs9taxRg@mail.gmail.com>
Date: Thu, 10 Feb 2022 20:05:15 +0200
From: Yehuda Yitchak <yehuda80@...il.com>
To: Florian Weimer <fweimer@...hat.com>
Cc: Rich Felker <dalias@...c.org>, musl@...ts.openwall.com
Subject: Re: Accessing Thread-Local-Storage in GDB
I forgot to mention I work on arm64
I guess there isn't much I can do at the moment, right ?
On Thu, Feb 10, 2022, 13:23 Florian Weimer <fweimer@...hat.com> wrote:
> * Rich Felker:
>
> > Indeed, I was just offering a quick workaround that might help, not
> > suggesting gdb should do that. __tls_get_addr can be used for
> > non-dynamic symbols with information already available to the
> > debugger. For core files you could probably simulate execution and
> > abort if anything is reached that would need to change process state
> > (lazy allocation) although that doesn't happen with musl anyway. But I
> > wonder if the core file even records the x86 segment information
> > needed to preserve thread pointer and simulate the %fs/%gs based
> > loads on x86[_64]..?
>
> The register is available as $fs_base on x86-64:
>
> (gdb) print (void *)$fs_base
> $1 = (void *) 0x7f2d12981740
> (gdb) print *(void **)$fs_base
> $2 = (void *) 0x7f2d12981740
>
> It probably does not work on i386 (even as $gs_base). I do not think it
> depends on FSGSBASE support in the kernel, but maybe I'm mistaken. I
> think I looked at this three years ago and couldn't make it work.
>
> Thanks,
> Florian
>
>
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