diff options
| -rw-r--r-- | arch/x86/include/asm/reboot.h | 5 | ||||
| -rw-r--r-- | arch/x86/kernel/Makefile | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/apm_32.c | 12 | ||||
| -rw-r--r-- | arch/x86/kernel/reboot.c | 120 | ||||
| -rw-r--r-- | arch/x86/kernel/reboot_32.S | 131 |
5 files changed, 162 insertions, 107 deletions
diff --git a/arch/x86/include/asm/reboot.h b/arch/x86/include/asm/reboot.h index 562d4fd31ba8..3250e3d605d9 100644 --- a/arch/x86/include/asm/reboot.h +++ b/arch/x86/include/asm/reboot.h @@ -18,7 +18,10 @@ extern struct machine_ops machine_ops; void native_machine_crash_shutdown(struct pt_regs *regs); void native_machine_shutdown(void); -void machine_real_restart(const unsigned char *code, int length); +void machine_real_restart(unsigned int type); +/* These must match dispatch_table in reboot_32.S */ +#define MRR_BIOS 0 +#define MRR_APM 1 typedef void (*nmi_shootdown_cb)(int, struct die_args*); void nmi_shootdown_cpus(nmi_shootdown_cb callback); diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index 2e8ce0deae4a..778c5b93676d 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -59,6 +59,7 @@ obj-$(CONFIG_STACKTRACE) += stacktrace.o obj-y += cpu/ obj-y += acpi/ obj-y += reboot.o +obj-$(CONFIG_X86_32) += reboot_32.o obj-$(CONFIG_MCA) += mca_32.o obj-$(CONFIG_X86_MSR) += msr.o obj-$(CONFIG_X86_CPUID) += cpuid.o diff --git a/arch/x86/kernel/apm_32.c b/arch/x86/kernel/apm_32.c index 0e4f24c2a746..b929108eb58f 100644 --- a/arch/x86/kernel/apm_32.c +++ b/arch/x86/kernel/apm_32.c @@ -975,20 +975,10 @@ recalc: static void apm_power_off(void) { - unsigned char po_bios_call[] = { - 0xb8, 0x00, 0x10, /* movw $0x1000,ax */ - 0x8e, 0xd0, /* movw ax,ss */ - 0xbc, 0x00, 0xf0, /* movw $0xf000,sp */ - 0xb8, 0x07, 0x53, /* movw $0x5307,ax */ - 0xbb, 0x01, 0x00, /* movw $0x0001,bx */ - 0xb9, 0x03, 0x00, /* movw $0x0003,cx */ - 0xcd, 0x15 /* int $0x15 */ - }; - /* Some bioses don't like being called from CPU != 0 */ if (apm_info.realmode_power_off) { set_cpus_allowed_ptr(current, cpumask_of(0)); - machine_real_restart(po_bios_call, sizeof(po_bios_call)); + machine_real_restart(MRR_APM); } else { (void)set_system_power_state(APM_STATE_OFF); } diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c index fc7aae1e2bc7..10c6619c0543 100644 --- a/arch/x86/kernel/reboot.c +++ b/arch/x86/kernel/reboot.c @@ -295,68 +295,16 @@ static int __init reboot_init(void) } core_initcall(reboot_init); -/* The following code and data reboots the machine by switching to real - mode and jumping to the BIOS reset entry point, as if the CPU has - really been reset. The previous version asked the keyboard - controller to pulse the CPU reset line, which is more thorough, but - doesn't work with at least one type of 486 motherboard. It is easy - to stop this code working; hence the copious comments. */ -static const unsigned long long -real_mode_gdt_entries [3] = -{ - 0x0000000000000000ULL, /* Null descriptor */ - 0x00009b000000ffffULL, /* 16-bit real-mode 64k code at 0x00000000 */ - 0x000093000100ffffULL /* 16-bit real-mode 64k data at 0x00000100 */ -}; +extern const unsigned char machine_real_restart_asm[]; +extern const u64 machine_real_restart_gdt[3]; -static const struct desc_ptr -real_mode_gdt = { sizeof (real_mode_gdt_entries) - 1, (long)real_mode_gdt_entries }, -real_mode_idt = { 0x3ff, 0 }; - -/* This is 16-bit protected mode code to disable paging and the cache, - switch to real mode and jump to the BIOS reset code. - - The instruction that switches to real mode by writing to CR0 must be - followed immediately by a far jump instruction, which set CS to a - valid value for real mode, and flushes the prefetch queue to avoid - running instructions that have already been decoded in protected - mode. - - Clears all the flags except ET, especially PG (paging), PE - (protected-mode enable) and TS (task switch for coprocessor state - save). Flushes the TLB after paging has been disabled. Sets CD and - NW, to disable the cache on a 486, and invalidates the cache. This - is more like the state of a 486 after reset. I don't know if - something else should be done for other chips. - - More could be done here to set up the registers as if a CPU reset had - occurred; hopefully real BIOSs don't assume much. */ -static const unsigned char real_mode_switch [] = -{ - 0x66, 0x0f, 0x20, 0xc0, /* movl %cr0,%eax */ - 0x66, 0x83, 0xe0, 0x11, /* andl $0x00000011,%eax */ - 0x66, 0x0d, 0x00, 0x00, 0x00, 0x60, /* orl $0x60000000,%eax */ - 0x66, 0x0f, 0x22, 0xc0, /* movl %eax,%cr0 */ - 0x66, 0x0f, 0x22, 0xd8, /* movl %eax,%cr3 */ - 0x66, 0x0f, 0x20, 0xc3, /* movl %cr0,%ebx */ - 0x66, 0x81, 0xe3, 0x00, 0x00, 0x00, 0x60, /* andl $0x60000000,%ebx */ - 0x74, 0x02, /* jz f */ - 0x0f, 0x09, /* wbinvd */ - 0x24, 0x10, /* f: andb $0x10,al */ - 0x66, 0x0f, 0x22, 0xc0 /* movl %eax,%cr0 */ -}; -static const unsigned char jump_to_bios [] = +void machine_real_restart(unsigned int type) { - 0xea, 0x00, 0x00, 0xff, 0xff /* ljmp $0xffff,$0x0000 */ -}; + void *restart_va; + unsigned long restart_pa; + void (*restart_lowmem)(unsigned int); + u64 *lowmem_gdt; -/* - * Switch to real mode and then execute the code - * specified by the code and length parameters. - * We assume that length will aways be less that 100! - */ -void machine_real_restart(const unsigned char *code, int length) -{ local_irq_disable(); /* Write zero to CMOS register number 0x0f, which the BIOS POST @@ -384,41 +332,23 @@ void machine_real_restart(const unsigned char *code, int length) too. */ *((unsigned short *)0x472) = reboot_mode; - /* For the switch to real mode, copy some code to low memory. It has - to be in the first 64k because it is running in 16-bit mode, and it - has to have the same physical and virtual address, because it turns - off paging. Copy it near the end of the first page, out of the way - of BIOS variables. */ - memcpy((void *)(0x1000 - sizeof(real_mode_switch) - 100), - real_mode_switch, sizeof (real_mode_switch)); - memcpy((void *)(0x1000 - 100), code, length); - - /* Set up the IDT for real mode. */ - load_idt(&real_mode_idt); - - /* Set up a GDT from which we can load segment descriptors for real - mode. The GDT is not used in real mode; it is just needed here to - prepare the descriptors. */ - load_gdt(&real_mode_gdt); - - /* Load the data segment registers, and thus the descriptors ready for - real mode. The base address of each segment is 0x100, 16 times the - selector value being loaded here. This is so that the segment - registers don't have to be reloaded after switching to real mode: - the values are consistent for real mode operation already. */ - __asm__ __volatile__ ("movl $0x0010,%%eax\n" - "\tmovl %%eax,%%ds\n" - "\tmovl %%eax,%%es\n" - "\tmovl %%eax,%%fs\n" - "\tmovl %%eax,%%gs\n" - "\tmovl %%eax,%%ss" : : : "eax"); - - /* Jump to the 16-bit code that we copied earlier. It disables paging - and the cache, switches to real mode, and jumps to the BIOS reset - entry point. */ - __asm__ __volatile__ ("ljmp $0x0008,%0" - : - : "i" ((void *)(0x1000 - sizeof (real_mode_switch) - 100))); + /* Patch the GDT in the low memory trampoline */ + lowmem_gdt = TRAMPOLINE_SYM(machine_real_restart_gdt); + + restart_va = TRAMPOLINE_SYM(machine_real_restart_asm); + restart_pa = virt_to_phys(restart_va); + restart_lowmem = (void (*)(unsigned int))restart_pa; + + /* GDT[0]: GDT self-pointer */ + lowmem_gdt[0] = + (u64)(sizeof(machine_real_restart_gdt) - 1) + + ((u64)virt_to_phys(lowmem_gdt) << 16); + /* GDT[1]: 64K real mode code segment */ + lowmem_gdt[1] = + GDT_ENTRY(0x009b, restart_pa, 0xffff); + + /* Jump to the identity-mapped low memory code */ + restart_lowmem(type); } #ifdef CONFIG_APM_MODULE EXPORT_SYMBOL(machine_real_restart); @@ -573,7 +503,7 @@ static void native_machine_emergency_restart(void) #ifdef CONFIG_X86_32 case BOOT_BIOS: - machine_real_restart(jump_to_bios, sizeof(jump_to_bios)); + machine_real_restart(MRR_BIOS); reboot_type = BOOT_KBD; break; diff --git a/arch/x86/kernel/reboot_32.S b/arch/x86/kernel/reboot_32.S new file mode 100644 index 000000000000..f242356a096e --- /dev/null +++ b/arch/x86/kernel/reboot_32.S @@ -0,0 +1,131 @@ +#include <linux/linkage.h> +#include <linux/init.h> +#include <asm/segment.h> +#include <asm/page_types.h> + +/* + * The following code and data reboots the machine by switching to real + * mode and jumping to the BIOS reset entry point, as if the CPU has + * really been reset. The previous version asked the keyboard + * controller to pulse the CPU reset line, which is more thorough, but + * doesn't work with at least one type of 486 motherboard. It is easy + * to stop this code working; hence the copious comments. + * + * This code is called with the restart type (0 = BIOS, 1 = APM) in %eax. + */ + .section ".x86_trampoline","a" + .balign 16 + .code32 +ENTRY(machine_real_restart_asm) +r_base = . + /* Get our own relocated address */ + call 1f +1: popl %ebx + subl $1b, %ebx + + /* Patch post-real-mode segment jump */ + movw dispatch_table(%ebx,%ecx,2),%cx + movw %cx, 101f(%ebx) + movw %ax, 102f(%ebx) + + /* Set up the IDT for real mode. */ + lidtl machine_real_restart_idt(%ebx) + + /* + * Set up a GDT from which we can load segment descriptors for real + * mode. The GDT is not used in real mode; it is just needed here to + * prepare the descriptors. + */ + lgdtl machine_real_restart_gdt(%ebx) + + /* + * Load the data segment registers with 16-bit compatible values + */ + movl $16, %ecx + movl %ecx, %ds + movl %ecx, %es + movl %ecx, %fs + movl %ecx, %gs + movl %ecx, %ss + ljmpl $8, $1f - r_base + +/* + * This is 16-bit protected mode code to disable paging and the cache, + * switch to real mode and jump to the BIOS reset code. + * + * The instruction that switches to real mode by writing to CR0 must be + * followed immediately by a far jump instruction, which set CS to a + * valid value for real mode, and flushes the prefetch queue to avoid + * running instructions that have already been decoded in protected + * mode. + * + * Clears all the flags except ET, especially PG (paging), PE + * (protected-mode enable) and TS (task switch for coprocessor state + * save). Flushes the TLB after paging has been disabled. Sets CD and + * NW, to disable the cache on a 486, and invalidates the cache. This + * is more like the state of a 486 after reset. I don't know if + * something else should be done for other chips. + * + * More could be done here to set up the registers as if a CPU reset had + * occurred; hopefully real BIOSs don't assume much. This is not the + * actual BIOS entry point, anyway (that is at 0xfffffff0). + * + * Most of this work is probably excessive, but it is what is tested. + */ + .code16 +1: + xorl %ecx, %ecx + movl %cr0, %eax + andl $0x00000011, %eax + orl $0x60000000, %eax + movl %eax, %cr0 + movl %ecx, %cr3 + movl %cr0, %edx + andl $0x60000000, %edx /* If no cache bits -> no wbinvd */ + jz 2f + wbinvd +2: + andb $0x10, %al + movl %eax, %cr0 + .byte 0xea /* ljmpw */ +101: .word 0 /* Offset */ +102: .word 0 /* Segment */ + +bios: + ljmpw $0xf000, $0xfff0 + +apm: + movw $0x1000, %ax + movw %ax, %ss + movw $0xf000, %sp + movw $0x5307, %ax + movw $0x0001, %bx + movw $0x0003, %cx + int $0x15 + +END(machine_real_restart_asm) + + .balign 16 + /* These must match <asm/reboot.h */ +dispatch_table: + .word bios - r_base + .word apm - r_base +END(dispatch_table) + + .balign 16 +machine_real_restart_idt: + .word 0xffff /* Length - real mode default value */ + .long 0 /* Base - real mode default value */ +END(machine_real_restart_idt) + + .balign 16 +ENTRY(machine_real_restart_gdt) + .quad 0 /* Self-pointer, filled in by PM code */ + .quad 0 /* 16-bit code segment, filled in by PM code */ + /* + * 16-bit data segment with the selector value 16 = 0x10 and + * base value 0x100; since this is consistent with real mode + * semantics we don't have to reload the segments once CR0.PE = 0. + */ + .quad GDT_ENTRY(0x0093, 0x100, 0xffff) +END(machine_real_restart_gdt) |