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x86: Add support for SW-switched segment-based protection domains

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This patch extends the protection domain framework with a third plugin
that is a hybrid of the previous two.  The hardware task switching
mechanism has a strictly-defined format for TSS data structures that
causes more space to be consumed than would otherwise be required.
This patch defines a smaller data structure that is allocated for each
protection domain, only requiring 32 bytes instead of 128 bytes.  It
uses the same multi-segment memory layout as the TSS-based plugin and
leaves paging disabled.  However, it uses a similar mechanism as the
paging plugin to perform system call dispatches and returns.

For additional information, please refer to cpu/x86/mm/README.md.
This commit is contained in:
Michael LeMay 2015-08-07 11:51:04 -07:00
parent 4cdb7ba9b6
commit e0aefd11d9
13 changed files with 335 additions and 38 deletions
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11
cpu/x86/mm/multi-segment.c
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@ -139,7 +139,14 @@ prot_domains_gdt_init()
(uint32_t)&_stext_addr,
((uint32_t)&_etext_addr) - (uint32_t)&_stext_addr,
SEG_FLAG(DPL, PRIV_LVL_EXC) | SEG_GRAN_BYTE |
SEG_DESCTYPE_NSYS | SEG_TYPE_CODE_EX);
SEG_DESCTYPE_NSYS |
#if X86_CONF_PROT_DOMAINS == X86_CONF_PROT_DOMAINS__SWSEG
/* The general protection fault handler requires read access to CS */
SEG_TYPE_CODE_EXRD
#else
SEG_TYPE_CODE_EX
#endif
);
gdt_insert_boot(GDT_IDX_CODE_EXC, desc);
segment_desc_init(&desc,
@ -180,7 +187,9 @@ prot_domains_gdt_init()
*/
desc.raw = SEG_DESC_NOT_PRESENT;
for(i = 0; i < PROT_DOMAINS_ACTUAL_CNT; i++) {
#if X86_CONF_PROT_DOMAINS == X86_CONF_PROT_DOMAINS__TSS
gdt_insert_boot(GDT_IDX_TSS(i), desc);
#endif
gdt_insert_boot(GDT_IDX_LDT(i), desc);
}