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Minor GDT fixes

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This commit is contained in:
Justin C. Miller
2018-05-20 01:02:50 -07:00
parent bfaab294e6
commit 814d6f1de6
3 changed files with 22 additions and 3 deletions
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3
src/kernel/boot.s
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@@ -28,7 +28,8 @@ _start:
extern kernel_main extern kernel_main
call kernel_main call kernel_main
; Kernel init is over, wait for interrupts ; Kernel init is over, wait for the scheduler to
; take over
.hang: .hang:
hlt hlt
jmp .hang jmp .hang

17
src/kernel/gdt.cpp
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@@ -137,10 +137,17 @@ idt_set_entry(uint8_t i, uint64_t addr, uint16_t selector, uint8_t flags)
void void
tss_set_stack(int ring, addr_t rsp) tss_set_stack(int ring, addr_t rsp)
{ {
kassert(ring < 3, "Bad ring passed to set_tss_stack."); kassert(ring < 3, "Bad ring passed to tss_set_stack.");
g_tss.rsp[ring] = rsp; g_tss.rsp[ring] = rsp;
} }
addr_t
tss_get_stack(int ring)
{
kassert(ring < 3, "Bad ring passed to tss_get_stack.");
return g_tss.rsp[ring];
}
void void
gdt_init() gdt_init()
{ {
@@ -150,12 +157,18 @@ gdt_init()
g_gdtr.limit = sizeof(g_gdt_table) - 1; g_gdtr.limit = sizeof(g_gdt_table) - 1;
g_gdtr.base = reinterpret_cast<uint64_t>(&g_gdt_table); g_gdtr.base = reinterpret_cast<uint64_t>(&g_gdt_table);
// Kernel CS/SS - always 64bit
gdt_set_entry(1, 0, 0xfffff, true, gdt_type::read_write | gdt_type::execute); gdt_set_entry(1, 0, 0xfffff, true, gdt_type::read_write | gdt_type::execute);
gdt_set_entry(2, 0, 0xfffff, true, gdt_type::read_write); gdt_set_entry(2, 0, 0xfffff, true, gdt_type::read_write);
gdt_set_entry(3, 0, 0xfffff, true, gdt_type::ring3 | gdt_type::read_write | gdt_type::execute);
// User CS32/SS/CS64 - layout expected by SYSRET
gdt_set_entry(3, 0, 0xfffff, false, gdt_type::ring3 | gdt_type::read_write | gdt_type::execute);
gdt_set_entry(4, 0, 0xfffff, true, gdt_type::ring3 | gdt_type::read_write); gdt_set_entry(4, 0, 0xfffff, true, gdt_type::ring3 | gdt_type::read_write);
gdt_set_entry(5, 0, 0xfffff, true, gdt_type::ring3 | gdt_type::read_write | gdt_type::execute);
kutil::memset(&g_tss, 0, sizeof(tss_entry)); kutil::memset(&g_tss, 0, sizeof(tss_entry));
g_tss.iomap_offset = sizeof(tss_entry);
addr_t tss_base = reinterpret_cast<addr_t>(&g_tss); addr_t tss_base = reinterpret_cast<addr_t>(&g_tss);
// Note that this takes TWO GDT entries // Note that this takes TWO GDT entries

5
src/kernel/gdt.h
View File

@@ -20,6 +20,11 @@ void idt_set_entry(uint8_t i, uint64_t addr, uint16_t selector, uint8_t flags);
/// \arg rsp Stack pointer to set /// \arg rsp Stack pointer to set
void tss_set_stack(int ring, addr_t rsp); void tss_set_stack(int ring, addr_t rsp);
/// Get the stack pointer for a given ring in the TSS
/// \arg ring Ring to get (0-2)
/// \returns Stack pointers for that ring
addr_t tss_get_stack(int ring);
/// Dump information about the current GDT to the screen /// Dump information about the current GDT to the screen
void gdt_dump(); void gdt_dump();