20054ae93f
Currently, the userland ABI uses a single field ('user_sp') far
into the very large 'kinfo' structure on the shared kernel
information page. This precludes us from modifying or getting
rid of 'kinfo' in the future without breaking userland. This
patch adds a separate 'kuserinfo' structure to the kernel
information page, with only information that is part of the
userland ABI, in an extensible manner. Userland now uses this
field if it is present, and falls back to the old field if not.
Change-Id: Ib7b24b53a440f40a2edc28cdfa48447ac2179288
63 lines
1.8 KiB
C
63 lines
1.8 KiB
C
/*
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* This file contains the main routine for retrieval of the kernel information
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* page, as well as abstraction routines for retrieval of specific values from
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* this kernel-mapped user information structure. These routines may be used
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* from both userland and system services, and their accesses are considered to
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* establish part of the userland ABI. Do not add routines here that are not
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* for retrieval of userland ABI fields (e.g., clock information)! Also, since
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* these functions are MINIX3 specific, their names should contain - preferably
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* be prefixed with - "minix_".
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*/
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#define _MINIX_SYSTEM
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#include <sys/cdefs.h>
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#include "namespace.h"
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#include <lib.h>
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#include <minix/param.h>
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#include <assert.h>
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extern struct minix_kerninfo *_minix_kerninfo;
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/*
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* Get a pointer to the kernel information page.
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*/
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struct minix_kerninfo *
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get_minix_kerninfo(void)
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{
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assert(_minix_kerninfo != NULL);
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return _minix_kerninfo;
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}
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/*
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* Obtain the initial stack pointer for a new userland process. This value
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* is used by routines that set up the stack when executing a new program.
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* It is used for userland exec(2) and in various system services.
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*/
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vir_bytes
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minix_get_user_sp(void)
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{
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struct minix_kerninfo *ki;
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/* All information is obtained from the kernel information page. */
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ki = get_minix_kerninfo();
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/*
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* Check whether we can retrieve the user stack pointer value from the
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* kuserinfo structure. In general, this test is the correct one to
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* see whether the kuserinfo structure has a certain field.
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*/
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if ((ki->ki_flags & MINIX_KIF_USERINFO) &&
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KUSERINFO_HAS_FIELD(ki->kuserinfo, kui_user_sp)) {
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return ki->kuserinfo->kui_user_sp;
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}
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/*
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* Otherwise, fall back to legacy support: retrieve the value from the
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* kinfo structure. This field will eventually be removed.
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*/
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return ki->kinfo->user_sp;
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}
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