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#include "arch/kernel/cpu/segment_register.hpp"
#include "arch/context_switching/interrupt_descriptor_table/segment_selector.hpp"
#include "arch/exception_handling/assert.hpp"
namespace teachos::arch::kernel::cpu
{
auto reload_data_segment_registers() -> void
{
asm volatile("xor %%rax, %%rax\n"
"mov %%rax, %%ss\n"
"mov %%rax, %%ds\n"
"mov %%rax, %%es\n"
"mov %%rax, %%fs\n"
"mov %%rax, %%gs\n"
: /* no output from call */
: /* no input to call */
: "rax");
}
auto set_data_segment_registers(context_switching::interrupt_descriptor_table::segment_selector data_segment) -> void
{
asm volatile("xor %%rax, %%rax\n"
"mov %[input], %%ax\n"
"mov %%rax, %%ds\n"
"mov %%rax, %%es\n"
"mov %%rax, %%fs\n"
"mov %%rax, %%gs\n"
: /* no output from call */
: [input] "m"(data_segment)
: "rax");
}
auto read_code_segment_register() -> context_switching::interrupt_descriptor_table::segment_selector
{
context_switching::interrupt_descriptor_table::segment_selector current_value{};
asm volatile("mov %%cs, %[output]" : [output] "=r"(current_value));
return current_value;
}
auto validate_data_segment_registers(context_switching::interrupt_descriptor_table::segment_selector data_segment)
-> void
{
context_switching::interrupt_descriptor_table::segment_selector ss{};
context_switching::interrupt_descriptor_table::segment_selector ds{};
context_switching::interrupt_descriptor_table::segment_selector es{};
context_switching::interrupt_descriptor_table::segment_selector fs{};
context_switching::interrupt_descriptor_table::segment_selector gs{};
asm volatile(
"mov %%ss, %[ss_output]\n"
"mov %%ds, %[ds_output]\n"
"mov %%es, %[es_output]\n"
"mov %%fs, %[fs_output]\n"
"mov %%gs, %[gs_output]\n"
: [ss_output] "=r"(ss), [ds_output] "=r"(ds), [es_output] "=r"(es), [fs_output] "=r"(fs), [gs_output] "=r"(gs));
auto result = (ss == ds && ss == es && ss == fs && ss == gs);
exception_handling::assert(result, "[Segment Register] Values in data register are not the same.");
result = (ss == data_segment);
exception_handling::assert(
result, "[Segment Register] Expected Data Segment is not the same as the value in the Stack Segment register.");
}
auto validate_code_segment_register(context_switching::interrupt_descriptor_table::segment_selector code_segment)
-> void
{
auto const cs = read_code_segment_register();
exception_handling::assert(
cs == code_segment,
"[Segment Register] Expected Code Segment is not the same as the value in the Code Segment register.");
}
auto validate_segment_registers(context_switching::interrupt_descriptor_table::segment_selector data_segment,
context_switching::interrupt_descriptor_table::segment_selector code_segment) -> void
{
validate_data_segment_registers(data_segment);
validate_code_segment_register(code_segment);
}
[[gnu::naked]]
auto set_code_segment_register(context_switching::interrupt_descriptor_table::segment_selector data_segment,
context_switching::interrupt_descriptor_table::segment_selector code_segment,
uint64_t address) -> void
{
asm volatile("mov %%rsp, %%rax\n"
"push %[data_segment]\n"
"push %%rax\n"
"pushfq\n"
"push %[code_segment]\n"
"mov %[return_function], %%rax\n"
"push %%rax\n"
"iretq\n"
: /* no output from call */
: [data_segment] "m"(data_segment), [code_segment] "m"(code_segment), [return_function] "r"(address)
: "rax");
}
} // namespace teachos::arch::kernel::cpu
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