Date: Tue, 18 Dec 2001 13:53:52 -0500 (EST) From: Andrew Gallatin <gallatin@cs.duke.edu> To: John Baldwin <jhb@FreeBSD.ORG> Cc: alpha@FreeBSD.ORG Subject: Re: mdproc flags in KSE Message-ID: <15391.37056.22312.225550@grasshopper.cs.duke.edu> In-Reply-To: <XFMail.011218100048.jhb@FreeBSD.org> References: <XFMail.011218100048.jhb@FreeBSD.org>
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John Baldwin writes:
> The alpha had several fields in its mdproc struct prior to KSE, and KSE stuck
> them all in mdthread, which isn't quite correct. Specifically, we have the
> following for mdthread now:
>
> struct mdthread {
> u_long md_flags;
> struct pcb *md_pcbpaddr; /* phys addr of the pcb */
> struct mdbpt md_sstep[2]; /* two single step breakpoints */
> u_int64_t md_hae; /* user HAE register value */
> void *osf_sigtramp; /* user-level signal trampoline */
> u_int md_kernnest; /* nesting level in the kernel */
> };
>
> #define MDP_FPUSED 0x0001 /* Process used the FPU */
> #define MDP_STEP1 0x0002 /* Single step normal instruction */
> #define MDP_STEP2 0x0004 /* Single step branch instruction */
> #define MDP_HAEUSED 0x0008 /* Process used the HAE */
> #define MDP_UAC_NOPRINT 0x0010 /* Don't print unaligned traps */
> #define MDP_UAC_NOFIX 0x0020 /* Don't fixup unaligned traps */
> #define MDP_UAC_SIGBUS 0x0040 /* Deliver SIGBUS upon
> unaligned access */
> #define MDP_UAC_MASK (MDP_UAC_NOPRINT | MDP_UAC_NOFIX | MDP_UAC_SIGBUS)
>
> Out of that structure, it seems obvious that md_pcbpaddr and md_kernnest need
> to be per-thread. It also seems that the UAC flags need to be
> per-process and need to move back into a md_flags in mdproc. However, I'm not
> sure about the other ones. What is the HAE and in what contexts is it used?
Its used by programs, like the X server, which grovel around in PCI
memory space... Hmm.. In a quick browse through the code, I don't see
where its actually used anymore..
> Also, what are the single stepping fields used for exactly (details, not just
> "to implement single stepping :)"). Is the osf_sigtramp just setup once for
Single-stepping -- no clue.
> the entire process, or does it have to be regenerated on the fly all the time?
Its used only by OSFF/ECOFF binaries. It is setup each time osf1_sigaction()
is called & used at sigreturn time to point to that process's
sigtramp code. Tru64 does'nt just keep it in a standard place like we
do.
Drew
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