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kernel: ldt support

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Matheus
2026-03-20 21:23:59 -03:00
parent a73c82f912
commit 41f97c6c61
17 changed files with 315 additions and 94 deletions
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kernel-src/arch/x86-64/context.c
+97 -81
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@@ -3,6 +3,7 @@
#include <arch/cpuid.h>
#include <kernel/slab.h>
#include <logging.h>
#include <arch/gdt.h>
#define XCR0_X87 (1ull << 0)
#define XCR0_SSE (1ull << 1)
@@ -12,120 +13,135 @@
#define XCR0_MASK (XCR0_AVX512 | XCR0_AVX | XCR0_SSE | XCR0_X87)
static enum {
FXSAVE,
XSAVE,
XSAVEOPT,
FXSAVE,
XSAVE,
XSAVEOPT,
} xsave_method;
size_t arch_xsave_size;
static uint64_t xcr0_value;
static scache_t *xsave_cache;
typedef struct {
uint16_t fcw;
uint16_t fsw;
uint8_t ftw;
uint8_t reserved1;
uint16_t fop;
uint64_t fip;
uint64_t fdp;
uint32_t mxcsr;
uint32_t mxcsr_mask;
struct {
uint64_t data[2];
} mm[8];
struct {
uint64_t data[2];
} xmm[16];
uint64_t reserved2[6];
uint64_t unused[6];
uint16_t fcw;
uint16_t fsw;
uint8_t ftw;
uint8_t reserved1;
uint16_t fop;
uint64_t fip;
uint64_t fdp;
uint32_t mxcsr;
uint32_t mxcsr_mask;
struct {
uint64_t data[2];
} mm[8];
struct {
uint64_t data[2];
} xmm[16];
uint64_t reserved2[6];
uint64_t unused[6];
} fxsave_area_t;
void arch_extracontext_detect(void) {
if (!arch_xsave_size) {
cpuid_results_t results;
cpuid(1, &results);
if (cpuid_base_max_leaf() >= 0x0d && (results.ecx & (1 << 26))) {
xsave_method = XSAVE;
if (!arch_xsave_size) {
cpuid_results_t results;
cpuid(1, &results);
if (cpuid_base_max_leaf() >= 0x0d && (results.ecx & (1 << 26))) {
xsave_method = XSAVE;
cpuid_with_ecx(0x0d, 0, &results);
xcr0_value = ((uint64_t)results.edx << 32) | results.eax;
xcr0_value &= XCR0_MASK;
} else {
xsave_method = FXSAVE;
arch_xsave_size = 512;
}
}
cpuid_with_ecx(0x0d, 0, &results);
xcr0_value = ((uint64_t)results.edx << 32) | results.eax;
xcr0_value &= XCR0_MASK;
} else {
xsave_method = FXSAVE;
arch_xsave_size = 512;
}
}
if (xsave_method == FXSAVE) return;
if (xsave_method == FXSAVE) return;
size_t cr4;
asm volatile("mov %%cr4, %0" : "=r" (cr4));
cr4 |= (1u << 18);
asm volatile("mov %0, %%cr4" :: "r" (cr4));
size_t cr4;
asm volatile("mov %%cr4, %0" : "=r" (cr4));
cr4 |= (1u << 18);
asm volatile("mov %0, %%cr4" :: "r" (cr4));
uint32_t low = xcr0_value;
uint32_t high = xcr0_value >> 32;
asm volatile("xsetbv" :: "a" (low), "d" (high), "c" (0u));
uint32_t low = xcr0_value;
uint32_t high = xcr0_value >> 32;
asm volatile("xsetbv" :: "a" (low), "d" (high), "c" (0u));
if (!arch_xsave_size) {
// after xsetbv ebx is updated to the size of the context for the enabled features
cpuid_results_t results;
cpuid_with_ecx(0x0d, 0, &results);
arch_xsave_size = results.ebx;
if (!arch_xsave_size) {
// after xsetbv ebx is updated to the size of the context for the enabled features
cpuid_results_t results;
cpuid_with_ecx(0x0d, 0, &results);
arch_xsave_size = results.ebx;
cpuid_with_ecx(0x0d, 1, &results);
if (results.eax & 1) xsave_method = XSAVEOPT;
}
cpuid_with_ecx(0x0d, 1, &results);
if (results.eax & 1) xsave_method = XSAVEOPT;
}
}
int arch_extracontext_init(extracontext_t *context) {
if (!xsave_cache) {
xsave_cache = slab_newcache(arch_xsave_size, xsave_method == FXSAVE ? 16 : 64, NULL, NULL);
__assert(xsave_cache);
}
if (!xsave_cache) {
xsave_cache = slab_newcache(arch_xsave_size, xsave_method == FXSAVE ? 16 : 64, NULL, NULL);
__assert(xsave_cache);
}
context->xsave = slab_allocate(xsave_cache);
if (!context->xsave) return 1;
context->xsave = slab_allocate(xsave_cache);
if (!context->xsave) return 1;
// all sse exceptions masked
// initialise the x87 FPU state as it would be after the FNINIT instruction
memset(context->xsave, 0, arch_xsave_size);
fxsave_area_t *area = context->xsave;
area->mxcsr = 0x1f80;
area->fcw = 0x37f;
// all sse exceptions masked
// initialise the x87 FPU state as it would be after the FNINIT instruction
memset(context->xsave, 0, arch_xsave_size);
fxsave_area_t *area = context->xsave;
area->mxcsr = 0x1f80;
area->fcw = 0x37f;
return 0;
return 0;
}
void arch_extracontext_free(extracontext_t *context) {
slab_free(xsave_cache, context->xsave);
slab_free(xsave_cache, context->xsave);
}
void arch_extracontext_save(extracontext_t *context) {
context->gsbase = rdmsr(MSR_KERNELGSBASE);
context->fsbase = rdmsr(MSR_FSBASE);
context->gsbase = rdmsr(MSR_KERNELGSBASE);
context->fsbase = rdmsr(MSR_FSBASE);
switch (xsave_method) {
case FXSAVE: asm("fxsaveq %0" ::"m"(*(char(*)[arch_xsave_size])context->xsave) : "memory"); break;
case XSAVE: asm("xsaveq %0" ::"m"(*(char(*)[arch_xsave_size])context->xsave), "d"(-1), "a"(-1) : "memory"); break;
case XSAVEOPT: asm("xsaveoptq %0" ::"m"(*(char(*)[arch_xsave_size])context->xsave), "d"(-1), "a"(-1) : "memory"); break;
}
asm volatile("mov %%gs, %0" : "=r"(context->gs));
asm volatile("mov %%fs, %0" : "=r"(context->fs));
switch (xsave_method) {
case FXSAVE: asm("fxsaveq %0" ::"m"(*(char(*)[arch_xsave_size])context->xsave) : "memory"); break;
case XSAVE: asm("xsaveq %0" ::"m"(*(char(*)[arch_xsave_size])context->xsave), "d"(-1), "a"(-1) : "memory"); break;
case XSAVEOPT: asm("xsaveoptq %0" ::"m"(*(char(*)[arch_xsave_size])context->xsave), "d"(-1), "a"(-1) : "memory"); break;
}
}
void arch_extracontext_load(extracontext_t *context) {
wrmsr(MSR_KERNELGSBASE, context->gsbase);
wrmsr(MSR_FSBASE, context->fsbase);
if (current_thread()->proc && current_thread()->proc->ldt)
arch_gdt_set_ldt(current_thread()->proc->ldt, 0xffff);
else
arch_gdt_set_ldt(NULL, 0);
switch (xsave_method) {
case FXSAVE: asm("fxrstorq %0" ::"m"(*(char(*)[arch_xsave_size])context->xsave) : "memory"); break;
case XSAVE:
case XSAVEOPT: asm("xrstorq %0" ::"m"(*(char(*)[arch_xsave_size])context->xsave), "d"(-1), "a"(-1) : "memory"); break;
}
void *old_base = current_cpu();
if (!load_seg_gs(context->gs)) load_seg_gs(0);
wrmsr(MSR_GSBASE, (uint64_t)old_base);
wrmsr(MSR_KERNELGSBASE, context->gsbase);
if (!load_seg_fs(context->fs)) load_seg_fs(0);
wrmsr(MSR_FSBASE, context->fsbase);
switch (xsave_method) {
case FXSAVE: asm("fxrstorq %0" ::"m"(*(char(*)[arch_xsave_size])context->xsave) : "memory"); break;
case XSAVE:
case XSAVEOPT: asm("xrstorq %0" ::"m"(*(char(*)[arch_xsave_size])context->xsave), "d"(-1), "a"(-1) : "memory"); break;
}
}
void arch_extracontext_copy(extracontext_t *dst, const extracontext_t *src) {
// XXX is this behavior correct? ucontext doesnt seem to save it on linux and so it will not be saved
dst->gsbase = src->gsbase;
dst->fsbase = src->fsbase;
memcpy(dst->xsave, src->xsave, arch_xsave_size);
// XXX is this behavior correct? ucontext doesnt seem to save it on linux and so it will not be saved
dst->gsbase = src->gsbase;
dst->fsbase = src->fsbase;
dst->fs = dst->fs;
dst->gs = dst->gs;
memcpy(dst->xsave, src->xsave, arch_xsave_size);
}