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From: istvan bak <bdhpfl@gmail.com>
To: 9front@9front.org
Subject: Re: [9front] exec suicide: sys: bad address in syscall
Date: Sun, 8 May 2022 21:45:14 +0000	[thread overview]
Message-ID: <CAO+DOcpjYFLu6V6NxewXDq_cUuOu55S06BsM9WV1jkyLTzvZqQ@mail.gmail.com> (raw)
In-Reply-To: <20220508151021.7cc0f0df@spruce.localdomain>

thank you for both answers. i should have figured this out on my own.
sorry for the noise.

On 08/05/2022, Amavect <amavect@gmail.com> wrote:
> On Sun, 8 May 2022 17:38:27 +0000
> istvan bak <bdhpfl@gmail.com> wrote:
>
>> term% 6.red 666: suicide: invalid address 0x7fff00000000/1 in sys call
>
>> 		execl("/bin/rc", "/bin/rc", "-c", cmd, 0);
>
> You have been bitten by varargs.
>
> The 4 bytes of 0x7fff00000000 is 32 bits.
> That 0 is a 32-bit integer.
> The 0 is not being converted due to varargs.
> Casting to (char*) or (void*) fixes your issue.
>
> See the warning when compiling this:
> print("%p", 0);
> warning: red.c:17 format mismatch p INT, arg 2
> This is a problem in every C implementation.
> Varargs suck.
>
> For fun, the disassembly:
> without casting (MOVL moves a 32 bit value):
> rc+0x42 0x000000000020006a	MOVL	$0x0,0x20(SP)
> rc+0x4a 0x0000000000200072	CALL	execl(SB)
>
> with casting (MOVQ moves a 64 bit value):
> rc+0x42 0x000000000020006a	MOVQ	$0x0,0x20(SP)
> rc+0x4b 0x0000000000200073	CALL	execl(SB)
>
> Note that run2() doesn't cast, either.
> You got lucky that the higher 32 bits are zero.
>
> Thanks,
> Amavect
>

      reply	other threads:[~2022-05-08 21:48 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-08 17:38 istvan bak
2022-05-08 19:53 ` ori
2022-05-08 20:10 ` Amavect
2022-05-08 21:45   ` istvan bak [this message]

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