From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <6a3ae47e0807080601m30b6da97w782bde83f91055cf@mail.gmail.com>
Date: Tue,  8 Jul 2008 14:01:27 +0100
From: "Robert Raschke" <rtrlists@googlemail.com>
To: "Fans of the OS Plan 9 from Bell Labs" <9fans@9fans.net>
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Subject: [9fans] P9P libthread on Debian ARM vs. makecontext et al.
Topicbox-Message-UUID: de24b9d0-ead3-11e9-9d60-3106f5b1d025

Hi,

I recently got myself a lovely Nokia N810 internet tablet. That runs
Debian ARM and I thought I'd have a stab at compiling P9P for it.
Unfortunately, the makecontext/swapcontext calls are not supported on
that platform by Debian.

I noticed that libthread/Linux.c has implementations of those two
functions for ARM. So I thought I try compiling libthread without
pthread support. This time, it's the mcontext_t (aka sigcontext)
struct that is causing an issue. The Debian ARM sigcontext struct
looks like this:

struct sigcontext {
    unsigned long trap_no;
    unsigned long error_code;
    unsigned long oldmask;
    unsigned long arm_r0;
...
    unsigned long arm_r10;
    unsigned long arm_fp;
    unsigned long arm_ip;
    unsigned long arm_sp;
    unsigned long arm_lr;
    unsigned long arm_pc;
    unsigned long arm_cpsr;
    unsigned long fault_address;
};

The code in Linux.c that implements makecontext() for ARM expects this
struct to contain a gregs array. I'm guessing that gregs is the same
as the enumerated arm_* ones above. So, would I be correct in assuming
that gregs[13] is arm_sp and gregs[14] is arm_lr?

Thanks,
Robby