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phunix/kernel/arch/i386/protect.c
Ben Gras ba05f39d1e kernel: some boottime sanitychecks 
. Check if we have the right number of boot modules
	. Check if the ELF parsing of VM actually succeeded

Both these are root causes of less-than-obvious other
errors/asserts a little further down the line; uncovered
while experimenting with booting by iPXE, specifically
(a) iPXE having a 8-multiboot-modules limit and
(b) trying to boot a gzipped VM.
2012-11-08 11:40:35 +01:00

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/* This file contains code for initialization of protected mode, to initialize
* code and data segment descriptors, and to initialize global descriptors
* for local descriptors in the process table.
*/
#include <string.h>
#include <assert.h>
#include <minix/cpufeature.h>
#include <machine/multiboot.h>
#include "kernel/kernel.h"
#include "archconst.h"
#include "arch_proto.h"
#include <libexec.h>
#define INT_GATE_TYPE (INT_286_GATE | DESC_386_BIT)
#define TSS_TYPE (AVL_286_TSS | DESC_386_BIT)
/* This is OK initially, when the 1:1 mapping is still there. */
char *video_mem = (char *) MULTIBOOT_VIDEO_BUFFER;
/* Storage for gdt, idt and tss. */
struct segdesc_s gdt[GDT_SIZE] __aligned(DESC_SIZE);
struct gatedesc_s idt[IDT_SIZE] __aligned(DESC_SIZE);
struct tss_s tss[CONFIG_MAX_CPUS];
u32_t k_percpu_stacks[CONFIG_MAX_CPUS];
int prot_init_done = 0;
phys_bytes vir2phys(void *vir)
{
extern char _kern_vir_base, _kern_phys_base; /* in kernel.lds */
u32_t offset = (vir_bytes) &_kern_vir_base -
(vir_bytes) &_kern_phys_base;
return (phys_bytes)vir - offset;
}
/*===========================================================================*
* enable_iop *
*===========================================================================*/
void enable_iop(struct proc *pp)
{
/* Allow a user process to use I/O instructions. Change the I/O Permission
* Level bits in the psw. These specify least-privileged Current Permission
* Level allowed to execute I/O instructions. Users and servers have CPL 3.
* You can't have less privilege than that. Kernel has CPL 0, tasks CPL 1.
*/
pp->p_reg.psw |= 0x3000;
}
/*===========================================================================*
* sdesc *
*===========================================================================*/
void sdesc(struct segdesc_s *segdp, phys_bytes base, vir_bytes size)
{
/* Fill in the size fields (base, limit and granularity) of a descriptor. */
segdp->base_low = base;
segdp->base_middle = base >> BASE_MIDDLE_SHIFT;
segdp->base_high = base >> BASE_HIGH_SHIFT;
--size; /* convert to a limit, 0 size means 4G */
if (size > BYTE_GRAN_MAX) {
segdp->limit_low = size >> PAGE_GRAN_SHIFT;
segdp->granularity = GRANULAR | (size >>
(PAGE_GRAN_SHIFT + GRANULARITY_SHIFT));
} else {
segdp->limit_low = size;
segdp->granularity = size >> GRANULARITY_SHIFT;
}
segdp->granularity |= DEFAULT; /* means BIG for data seg */
}
/*===========================================================================*
* init_dataseg *
*===========================================================================*/
void init_param_dataseg(register struct segdesc_s *segdp,
phys_bytes base, vir_bytes size, const int privilege)
{
/* Build descriptor for a data segment. */
sdesc(segdp, base, size);
segdp->access = (privilege << DPL_SHIFT) | (PRESENT | SEGMENT |
WRITEABLE | ACCESSED);
/* EXECUTABLE = 0, EXPAND_DOWN = 0, ACCESSED = 0 */
}
void init_dataseg(int index, const int privilege)
{
init_param_dataseg(&gdt[index], 0, 0xFFFFFFFF, privilege);
}
/*===========================================================================*
* init_codeseg *
*===========================================================================*/
static void init_codeseg(int index, int privilege)
{
/* Build descriptor for a code segment. */
sdesc(&gdt[index], 0, 0xFFFFFFFF);
gdt[index].access = (privilege << DPL_SHIFT)
| (PRESENT | SEGMENT | EXECUTABLE | READABLE);
/* CONFORMING = 0, ACCESSED = 0 */
}
static struct gate_table_s gate_table_pic[] = {
{ hwint00, VECTOR( 0), INTR_PRIVILEGE },
{ hwint01, VECTOR( 1), INTR_PRIVILEGE },
{ hwint02, VECTOR( 2), INTR_PRIVILEGE },
{ hwint03, VECTOR( 3), INTR_PRIVILEGE },
{ hwint04, VECTOR( 4), INTR_PRIVILEGE },
{ hwint05, VECTOR( 5), INTR_PRIVILEGE },
{ hwint06, VECTOR( 6), INTR_PRIVILEGE },
{ hwint07, VECTOR( 7), INTR_PRIVILEGE },
{ hwint08, VECTOR( 8), INTR_PRIVILEGE },
{ hwint09, VECTOR( 9), INTR_PRIVILEGE },
{ hwint10, VECTOR(10), INTR_PRIVILEGE },
{ hwint11, VECTOR(11), INTR_PRIVILEGE },
{ hwint12, VECTOR(12), INTR_PRIVILEGE },
{ hwint13, VECTOR(13), INTR_PRIVILEGE },
{ hwint14, VECTOR(14), INTR_PRIVILEGE },
{ hwint15, VECTOR(15), INTR_PRIVILEGE },
{ NULL, 0, 0}
};
static struct gate_table_s gate_table_exceptions[] = {
{ divide_error, DIVIDE_VECTOR, INTR_PRIVILEGE },
{ single_step_exception, DEBUG_VECTOR, INTR_PRIVILEGE },
{ nmi, NMI_VECTOR, INTR_PRIVILEGE },
{ breakpoint_exception, BREAKPOINT_VECTOR, USER_PRIVILEGE },
{ overflow, OVERFLOW_VECTOR, USER_PRIVILEGE },
{ bounds_check, BOUNDS_VECTOR, INTR_PRIVILEGE },
{ inval_opcode, INVAL_OP_VECTOR, INTR_PRIVILEGE },
{ copr_not_available, COPROC_NOT_VECTOR, INTR_PRIVILEGE },
{ double_fault, DOUBLE_FAULT_VECTOR, INTR_PRIVILEGE },
{ copr_seg_overrun, COPROC_SEG_VECTOR, INTR_PRIVILEGE },
{ inval_tss, INVAL_TSS_VECTOR, INTR_PRIVILEGE },
{ segment_not_present, SEG_NOT_VECTOR, INTR_PRIVILEGE },
{ stack_exception, STACK_FAULT_VECTOR, INTR_PRIVILEGE },
{ general_protection, PROTECTION_VECTOR, INTR_PRIVILEGE },
{ page_fault, PAGE_FAULT_VECTOR, INTR_PRIVILEGE },
{ copr_error, COPROC_ERR_VECTOR, INTR_PRIVILEGE },
{ alignment_check, ALIGNMENT_CHECK_VECTOR, INTR_PRIVILEGE },
{ machine_check, MACHINE_CHECK_VECTOR, INTR_PRIVILEGE },
{ simd_exception, SIMD_EXCEPTION_VECTOR, INTR_PRIVILEGE },
{ ipc_entry_softint_orig, IPC_VECTOR_ORIG, USER_PRIVILEGE },
{ kernel_call_entry_orig, KERN_CALL_VECTOR_ORIG, USER_PRIVILEGE },
{ ipc_entry_softint_um, IPC_VECTOR_UM, USER_PRIVILEGE },
{ kernel_call_entry_um, KERN_CALL_VECTOR_UM, USER_PRIVILEGE },
{ NULL, 0, 0}
};
int tss_init(unsigned cpu, void * kernel_stack)
{
struct tss_s * t = &tss[cpu];
int index = TSS_INDEX(cpu);
struct segdesc_s *tssgdt;
tssgdt = &gdt[index];
init_param_dataseg(tssgdt, (phys_bytes) t,
sizeof(struct tss_s), INTR_PRIVILEGE);
tssgdt->access = PRESENT | (INTR_PRIVILEGE << DPL_SHIFT) | TSS_TYPE;
/* Build TSS. */
memset(t, 0, sizeof(*t));
t->ds = t->es = t->fs = t->gs = t->ss0 = KERN_DS_SELECTOR;
t->cs = KERN_CS_SELECTOR;
t->iobase = sizeof(struct tss_s); /* empty i/o permissions map */
/*
* make space for process pointer and cpu id and point to the first
* usable word
*/
k_percpu_stacks[cpu] = t->sp0 = ((unsigned) kernel_stack) - X86_STACK_TOP_RESERVED;
/*
* set the cpu id at the top of the stack so we know on which cpu is
* this stak in use when we trap to kernel
*/
*((reg_t *)(t->sp0 + 1 * sizeof(reg_t))) = cpu;
/* Set up Intel SYSENTER support if available. */
if(minix_feature_flags & MKF_I386_INTEL_SYSENTER) {
ia32_msr_write(INTEL_MSR_SYSENTER_CS, 0, KERN_CS_SELECTOR);
ia32_msr_write(INTEL_MSR_SYSENTER_ESP, 0, t->sp0);
ia32_msr_write(INTEL_MSR_SYSENTER_EIP, 0, (u32_t) ipc_entry_sysenter);
}
/* Set up AMD SYSCALL support if available. */
if(minix_feature_flags & MKF_I386_AMD_SYSCALL) {
u32_t msr_lo, msr_hi;
/* set SYSCALL ENABLE bit in EFER MSR */
ia32_msr_read(AMD_MSR_EFER, &msr_hi, &msr_lo);
msr_lo |= AMD_EFER_SCE;
ia32_msr_write(AMD_MSR_EFER, msr_hi, msr_lo);
/* set STAR register value */
#define set_star_cpu(forcpu) if(cpu == forcpu) { \
ia32_msr_write(AMD_MSR_STAR, \
((u32_t)USER_CS_SELECTOR << 16) | (u32_t)KERN_CS_SELECTOR, \
(u32_t) ipc_entry_syscall_cpu ## forcpu); }
set_star_cpu(0);
set_star_cpu(1);
set_star_cpu(2);
set_star_cpu(3);
set_star_cpu(4);
set_star_cpu(5);
set_star_cpu(6);
set_star_cpu(7);
assert(CONFIG_MAX_CPUS <= 8);
}
return SEG_SELECTOR(index);
}
phys_bytes init_segdesc(int gdt_index, void *base, int size)
{
struct desctableptr_s *dtp = (struct desctableptr_s *) &gdt[gdt_index];
dtp->limit = size - 1;
dtp->base = (phys_bytes) base;
return (phys_bytes) dtp;
}
void int_gate(struct gatedesc_s *tab,
unsigned vec_nr, vir_bytes offset, unsigned dpl_type)
{
/* Build descriptor for an interrupt gate. */
register struct gatedesc_s *idp;
idp = &tab[vec_nr];
idp->offset_low = offset;
idp->selector = KERN_CS_SELECTOR;
idp->p_dpl_type = dpl_type;
idp->offset_high = offset >> OFFSET_HIGH_SHIFT;
}
void int_gate_idt(unsigned vec_nr, vir_bytes offset, unsigned dpl_type)
{
int_gate(idt, vec_nr, offset, dpl_type);
}
void idt_copy_vectors(struct gate_table_s * first)
{
struct gate_table_s *gtp;
for (gtp = first; gtp->gate; gtp++) {
int_gate(idt, gtp->vec_nr, (vir_bytes) gtp->gate,
PRESENT | INT_GATE_TYPE |
(gtp->privilege << DPL_SHIFT));
}
}
void idt_copy_vectors_pic(void)
{
idt_copy_vectors(gate_table_pic);
}
void idt_init(void)
{
idt_copy_vectors_pic();
idt_copy_vectors(gate_table_exceptions);
}
struct desctableptr_s gdt_desc, idt_desc;
void idt_reload(void)
{
x86_lidt(&idt_desc);
}
multiboot_module_t *bootmod(int pnr)
{
int i;
assert(pnr >= 0);
/* Search for desired process in boot process
* list. The first NR_TASKS ones do not correspond
* to a module, however, so we don't search those.
*/
for(i = NR_TASKS; i < NR_BOOT_PROCS; i++) {
int p;
p = i - NR_TASKS;
if(image[i].proc_nr == pnr) {
assert(p < MULTIBOOT_MAX_MODS);
assert(p < kinfo.mbi.mods_count);
return &kinfo.module_list[p];
}
}
panic("boot module %d not found", pnr);
}
int booting_cpu = 0;
void prot_load_selectors(void)
{
/* this function is called by both prot_init by the BSP and
* the early AP booting code in mpx.S by secondary CPU's.
* everything is set up the same except for the TSS that is per-CPU.
*/
x86_lgdt(&gdt_desc); /* Load gdt */
idt_init();
idt_reload();
x86_lldt(LDT_SELECTOR); /* Load bogus ldt */
x86_ltr(TSS_SELECTOR(booting_cpu));
x86_load_kerncs();
x86_load_ds(KERN_DS_SELECTOR);
x86_load_es(KERN_DS_SELECTOR);
x86_load_fs(KERN_DS_SELECTOR);
x86_load_gs(KERN_DS_SELECTOR);
x86_load_ss(KERN_DS_SELECTOR);
}
/*===========================================================================*
* prot_init *
*===========================================================================*/
void prot_init()
{
extern char k_boot_stktop;
if(_cpufeature(_CPUF_I386_SYSENTER))
minix_feature_flags |= MKF_I386_INTEL_SYSENTER;
if(_cpufeature(_CPUF_I386_SYSCALL))
minix_feature_flags |= MKF_I386_AMD_SYSCALL;
memset(gdt, 0, sizeof(gdt));
memset(idt, 0, sizeof(idt));
/* Build GDT, IDT, IDT descriptors. */
gdt_desc.base = (u32_t) gdt;
gdt_desc.limit = sizeof(gdt)-1;
idt_desc.base = (u32_t) idt;
idt_desc.limit = sizeof(idt)-1;
tss_init(0, &k_boot_stktop);
/* Build GDT */
init_param_dataseg(&gdt[LDT_INDEX],
(phys_bytes) 0, 0, INTR_PRIVILEGE); /* unusable LDT */
gdt[LDT_INDEX].access = PRESENT | LDT;
init_codeseg(KERN_CS_INDEX, INTR_PRIVILEGE);
init_dataseg(KERN_DS_INDEX, INTR_PRIVILEGE);
init_codeseg(USER_CS_INDEX, USER_PRIVILEGE);
init_dataseg(USER_DS_INDEX, USER_PRIVILEGE);
/* Currently the multiboot segments are loaded; which is fine, but
* let's replace them with the ones from our own GDT so we test
* right away whether they work as expected.
*/
prot_load_selectors();
/* Set up a new post-relocate bootstrap pagetable so that
* we can map in VM, and we no longer rely on pre-relocated
* data.
*/
pg_clear();
pg_identity(&kinfo); /* Still need 1:1 for lapic and video mem and such. */
pg_mapkernel();
pg_load();
prot_init_done = 1;
}
static int alloc_for_vm = 0;
void arch_post_init(void)
{
/* Let memory mapping code know what's going on at bootstrap time */
struct proc *vm;
vm = proc_addr(VM_PROC_NR);
get_cpulocal_var(ptproc) = vm;
pg_info(&vm->p_seg.p_cr3, &vm->p_seg.p_cr3_v);
}
int libexec_pg_alloc(struct exec_info *execi, off_t vaddr, size_t len)
{
pg_map(PG_ALLOCATEME, vaddr, vaddr+len, &kinfo);
pg_load();
memset((char *) vaddr, 0, len);
alloc_for_vm += len;
return OK;
}
void arch_boot_proc(struct boot_image *ip, struct proc *rp)
{
multiboot_module_t *mod;
if(rp->p_nr < 0) return;
mod = bootmod(rp->p_nr);
/* Important special case: we put VM in the bootstrap pagetable
* so it can run.
*/
if(rp->p_nr == VM_PROC_NR) {
struct exec_info execi;
memset(&execi, 0, sizeof(execi));
/* exec parameters */
execi.stack_high = kinfo.user_sp;
execi.stack_size = 16 * 1024; /* not too crazy as it must be preallocated */
execi.proc_e = ip->endpoint;
execi.hdr = (char *) mod->mod_start; /* phys mem direct */
execi.hdr_len = mod->mod_end - mod->mod_start;
strlcpy(execi.progname, ip->proc_name, sizeof(execi.progname));
execi.frame_len = 0;
/* callbacks for use in the kernel */
execi.copymem = libexec_copy_memcpy;
execi.clearmem = libexec_clear_memset;
execi.allocmem_prealloc = libexec_pg_alloc;
execi.allocmem_ondemand = libexec_pg_alloc;
execi.clearproc = NULL;
/* parse VM ELF binary and alloc/map it into bootstrap pagetable */
if(libexec_load_elf(&execi) != OK)
panic("VM loading failed");
/* Initialize the server stack pointer. Take it down three words
* to give startup code something to use as "argc", "argv" and "envp".
*/
arch_proc_init(rp, execi.pc, kinfo.user_sp - 3*4, ip->proc_name);
/* Free VM blob that was just copied into existence. */
cut_memmap(&kinfo, mod->mod_start, mod->mod_end);
/* Remember them */
kinfo.vm_allocated_bytes = alloc_for_vm;
}
}
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