linux-kernel - Re: [PATCH 2/5] ptrace: implement PTRACE

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Date:	Sat, 18 Jun 2011 09:55:37 +0200
From:	Denys Vlasenko <vda.linux@...glemail.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	oleg@...hat.com, jan.kratochvil@...hat.com,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, indan@....nu, bdonlan@...il.com,
	pedro@...esourcery.com
Subject: Re: [PATCH 2/5] ptrace: implement PTRACE_SEIZE

On Tuesday 14 June 2011 11:20, Tejun Heo wrote:
   #define PTRACE_EVENT_FORK    1
   #define PTRACE_EVENT_VFORK   2
   #define PTRACE_EVENT_CLONE   3
>  #define PTRACE_EVENT_EXEC	4
>  #define PTRACE_EVENT_VFORK_DONE	5
>  #define PTRACE_EVENT_EXIT	6
> +#define PTRACE_EVENT_STOP	7

Er... these constants were corresponding exactly to
bit positions in ptrace options which enable them:

#define PTRACE_O_TRACESYSGOOD   0x00000001
#define PTRACE_O_TRACEFORK      0x00000002
#define PTRACE_O_TRACEVFORK     0x00000004
#define PTRACE_O_TRACECLONE     0x00000008
#define PTRACE_O_TRACEEXEC      0x00000010
#define PTRACE_O_TRACEVFORKDONE 0x00000020
#define PTRACE_O_TRACEEXIT      0x00000040

For example, PTRACE_O_TRACEEXEC is 4th bit, PTRACE_EVENT_EXEC is 4.

If we'd define PTRACE_EVENT_STOP as 7, any future added
PTRACE_O_foo bit with value 0x00000080 will be unable
to follow this convention.

I propose to define PTRACE_EVENT_STOP as 64 instead, leaving 64 low
PTRACE_EVENT_foo constants for possible future PTRACE_O_foo bits.

[32 should be enough too, but I feel paranoid today :)]

-- 
vda

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