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Message-Id: <4885CEFE.76E4.0078.0@novell.com>
Date: Tue, 22 Jul 2008 11:13:50 +0100
From: "Jan Beulich" <jbeulich@...ell.com>
To: "Ingo Molnar" <mingo@...e.hu>
Cc: "Andi Kleen" <andi@...stfloor.org>, <tglx@...utronix.de>,
<linux-kernel@...r.kernel.org>, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] i386: improve double fault handling
>>> Ingo Molnar <mingo@...e.hu> 21.07.08 13:05 >>>
>this still doesnt apply to latest -git. (or tip/master)
Indeed, tip/master had a __pa -> __phys_addr_const conversion that
I now sync-ed the patch with (without another round of testing):
Make the double fault handler use CPU-specific stacks. Add some
abstraction to simplify future change of other exception handlers to go
through task gates.
Add a new notification of the event through the die notifier chain,
also providing some environmental adjustments so that various
infrastructural things work independent of the fact that the fault and
the callbacks are running on other then the normal kernel stack.
Signed-Off-By: Jan Beulich <jbeulich@...ell.com>
Cc: Andi Kleen <andi@...stfloor.org>
---
arch/x86/kernel/cpu/common.c | 17 +++++--
arch/x86/kernel/doublefault_32.c | 86 ++++++++++++++++++++++++---------------
arch/x86/kernel/smpboot.c | 44 +++++++++++++++++++
arch/x86/kernel/traps_32.c | 51 ++++++++++++++++++++++-
drivers/lguest/segments.c | 3 -
include/asm-x86/kdebug.h | 1
include/asm-x86/processor.h | 7 ++-
include/asm-x86/segment.h | 15 ++++--
include/asm-x86/thread_info_32.h | 9 +++-
9 files changed, 187 insertions(+), 46 deletions(-)
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -650,6 +650,13 @@ void switch_to_new_gdt(void)
asm("mov %0, %%fs" : : "r" (__KERNEL_PERCPU) : "memory");
}
+static void *__init_refok alloc_boot_stack(void)
+{
+ BUILD_BUG_ON(EXCEPTION_STACK_ORDER > THREAD_ORDER);
+ return __alloc_bootmem(EXCEPTION_STACK_SIZE, THREAD_SIZE,
+ __phys_addr_const(MAX_DMA_ADDRESS));
+}
+
/*
* cpu_init() initializes state that is per-CPU. Some data is already
* initialized (naturally) in the bootstrap process, such as the GDT
@@ -690,10 +697,12 @@ void __cpuinit cpu_init(void)
load_TR_desc();
load_LDT(&init_mm.context);
-#ifdef CONFIG_DOUBLEFAULT
- /* Set up doublefault TSS pointer in the GDT */
- __set_tss_desc(cpu, GDT_ENTRY_DOUBLEFAULT_TSS, &doublefault_tss);
-#endif
+ if (cpu == 0) {
+ unsigned i;
+
+ for (i = 0; i < N_EXCEPTION_TSS; ++i)
+ setup_exception_tss(cpu, i, alloc_boot_stack);
+ }
/* Clear %gs. */
asm volatile ("mov %0, %%gs" : : "r" (0));
--- a/arch/x86/kernel/doublefault_32.c
+++ b/arch/x86/kernel/doublefault_32.c
@@ -3,69 +3,89 @@
#include <linux/init.h>
#include <linux/init_task.h>
#include <linux/fs.h>
+#include <linux/kdebug.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/processor.h>
#include <asm/desc.h>
-#define DOUBLEFAULT_STACKSIZE (1024)
-static unsigned long doublefault_stack[DOUBLEFAULT_STACKSIZE];
-#define STACK_START (unsigned long)(doublefault_stack+DOUBLEFAULT_STACKSIZE)
+#define ptr_ok(x, l) ((x) >= PAGE_OFFSET && (x) + (l) < (unsigned long)high_memory)
-#define ptr_ok(x) ((x) > PAGE_OFFSET && (x) < PAGE_OFFSET + MAXMEM)
+#define THREAD_INFO_FROM(x) ((struct thread_info *)((x) & ~(THREAD_SIZE - 1)))
-static void doublefault_fn(void)
+register const struct x86_hw_tss *self __asm__("ebx");
+
+void doublefault_fn(void)
{
- struct desc_ptr gdt_desc = {0, 0};
+ struct desc_ptr gdt_desc;
unsigned long gdt, tss;
store_gdt(&gdt_desc);
gdt = gdt_desc.address;
- printk(KERN_EMERG "PANIC: double fault, gdt at %08lx [%d bytes]\n", gdt, gdt_desc.size);
+ printk(KERN_EMERG "PANIC: double fault on CPU#%lu, gdt at %08lx [%d bytes]\n",
+ self->sp2, gdt, gdt_desc.size + 1);
- if (ptr_ok(gdt)) {
+ if (ptr_ok(gdt, gdt_desc.size)) {
gdt += GDT_ENTRY_TSS << 3;
tss = *(u16 *)(gdt+2);
tss += *(u8 *)(gdt+4) << 16;
tss += *(u8 *)(gdt+7) << 24;
printk(KERN_EMERG "double fault, tss at %08lx\n", tss);
- if (ptr_ok(tss)) {
- struct x86_hw_tss *t = (struct x86_hw_tss *)tss;
+ if (ptr_ok(tss, *(u16 *)gdt)) {
+ const struct x86_hw_tss *t = (struct x86_hw_tss *)tss;
+ struct {
+ struct pt_regs common;
+ struct {
+ unsigned long es;
+ unsigned long ds;
+ unsigned long fs;
+ unsigned long gs;
+ } vm86;
+ } regs;
+
+ /* for current/current_thread_info to work... */
+ *THREAD_INFO_FROM(self->sp) = *THREAD_INFO_FROM(t->sp0 - 1);
printk(KERN_EMERG "eip = %08lx, esp = %08lx\n",
t->ip, t->sp);
printk(KERN_EMERG "eax = %08lx, ebx = %08lx, ecx = %08lx, edx = %08lx\n",
t->ax, t->bx, t->cx, t->dx);
- printk(KERN_EMERG "esi = %08lx, edi = %08lx\n",
- t->si, t->di);
+ printk(KERN_EMERG "esi = %08lx, edi = %08lx, ebp = %08lx\n",
+ t->si, t->di, t->bp);
+
+ regs.common.bx = t->bx;
+ regs.common.cx = t->cx;
+ regs.common.dx = t->dx;
+ regs.common.si = t->si;
+ regs.common.di = t->di;
+ regs.common.bp = t->bp;
+ regs.common.ax = t->ax;
+ regs.common.ds = t->ds;
+ regs.common.es = t->es;
+ regs.common.fs = t->fs;
+ regs.common.orig_ax = -1;
+ regs.common.ip = t->ip;
+ regs.common.cs = t->cs;
+ regs.common.flags = t->flags;
+ regs.common.sp = t->sp;
+ regs.common.ss = t->ss;
+ if (t->flags & X86_EFLAGS_VM) {
+ regs.common.ds = 0;
+ regs.common.es = 0;
+ regs.common.fs = 0;
+ regs.vm86.es = t->es;
+ regs.vm86.ds = t->ds;
+ regs.vm86.fs = t->fs;
+ regs.vm86.gs = t->gs;
+ }
+ notify_die(DIE_DOUBLE_FAULT, "double fault", ®s.common, 0, 8, SIGKILL);
}
}
for (;;)
cpu_relax();
}
-
-struct tss_struct doublefault_tss __cacheline_aligned = {
- .x86_tss = {
- .sp0 = STACK_START,
- .ss0 = __KERNEL_DS,
- .ldt = 0,
- .io_bitmap_base = INVALID_IO_BITMAP_OFFSET,
-
- .ip = (unsigned long) doublefault_fn,
- /* 0x2 bit is always set */
- .flags = X86_EFLAGS_SF | 0x2,
- .sp = STACK_START,
- .es = __USER_DS,
- .cs = __KERNEL_CS,
- .ss = __KERNEL_DS,
- .ds = __USER_DS,
- .fs = __KERNEL_PERCPU,
-
- .__cr3 = __phys_addr_const((unsigned long)swapper_pg_dir)
- }
-};
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -762,6 +762,45 @@ static void __cpuinit do_fork_idle(struc
complete(&c_idle->done);
}
+#ifdef CONFIG_X86_32
+static int __cpuinit map_exception_stack(pte_t *pte, struct page *pmd_page,
+ unsigned long addr, void *data)
+{
+ struct page **pages = data;
+
+ *pte = mk_pte(pages[(addr >> PAGE_SHIFT)
+ & ((1 << EXCEPTION_STACK_ORDER) - 1)],
+ PAGE_KERNEL);
+ return 0;
+}
+
+static void *__cpuinit alloc_exception_stack(void)
+{
+ struct vm_struct *area;
+ void *stack;
+ unsigned int i;
+ struct page *pages[1 << EXCEPTION_STACK_ORDER];
+
+ BUILD_BUG_ON(EXCEPTION_STACK_ORDER > THREAD_ORDER);
+ /* Try not wasting virtual space. */
+ for (i = EXCEPTION_STACK_SIZE; i < 2 * THREAD_SIZE; i += PAGE_SIZE) {
+ area = get_vm_area(i, 0);
+ BUG_ON(!area);
+ stack = PTR_ALIGN(area->addr, THREAD_SIZE);
+ if (stack + EXCEPTION_STACK_SIZE <= area->addr + i)
+ break;
+ free_vm_area(area);
+ }
+ for (i = 0; !(i >> EXCEPTION_STACK_ORDER); ++i) {
+ pages[i] = alloc_page(GFP_KERNEL|__GFP_HIGHMEM);
+ BUG_ON(!pages[i]);
+ }
+ apply_to_page_range(&init_mm, (unsigned long)stack,
+ EXCEPTION_STACK_SIZE, map_exception_stack, pages);
+ return stack;
+}
+#endif
+
#ifdef CONFIG_X86_64
/*
* Allocate node local memory for the AP pda.
@@ -862,6 +901,11 @@ do_rest:
init_gdt(cpu);
/* Stack for startup_32 can be just as for start_secondary onwards */
irq_ctx_init(cpu);
+#define i start_ip
+ for (i = 0; i < N_EXCEPTION_TSS; ++i)
+ setup_exception_tss(cpu, i, alloc_exception_stack);
+ vmalloc_sync_all();
+#undef i
#else
cpu_pda(cpu)->pcurrent = c_idle.idle;
clear_tsk_thread_flag(c_idle.idle, TIF_FORK);
--- a/arch/x86/kernel/traps_32.c
+++ b/arch/x86/kernel/traps_32.c
@@ -66,6 +66,29 @@ EXPORT_SYMBOL_GPL(used_vectors);
asmlinkage int system_call(void);
+#if N_EXCEPTION_TSS
+void doublefault_fn(void);
+
+static DEFINE_PER_CPU(struct x86_hw_tss[N_EXCEPTION_TSS], exception_tss) =
+{
+ [0 ... N_EXCEPTION_TSS-1] =
+ {
+ .cs = __KERNEL_CS,
+ .ss = __KERNEL_DS,
+ .ss0 = __KERNEL_DS,
+ .__cr3 = __phys_addr_const((unsigned long)swapper_pg_dir),
+ .io_bitmap_base = INVALID_IO_BITMAP_OFFSET,
+ .ds = __USER_DS,
+ .es = __USER_DS,
+ .fs = __KERNEL_PERCPU,
+ .flags = X86_EFLAGS_SF | 0x2, /* 0x2 bit is always set */
+ },
+#ifdef CONFIG_DOUBLEFAULT
+ [DOUBLEFAULT_TSS].ip = (unsigned long)doublefault_fn
+#endif
+};
+#endif
+
/* Do we ignore FPU interrupts ? */
char ignore_fpu_irq;
@@ -1185,6 +1208,30 @@ asmlinkage void math_emulate(long arg)
#endif /* CONFIG_MATH_EMULATION */
+#if N_EXCEPTION_TSS
+void __cpuinit setup_exception_tss(unsigned int cpu, unsigned int idx,
+ void *(*alloc_stack)(void))
+{
+ struct x86_hw_tss *tss = per_cpu(exception_tss, cpu) + idx;
+
+ /* Set up exception handling TSS. */
+ tss->bx = (unsigned long)tss;
+ tss->sp2 = cpu;
+
+ /* Set up exception handling stack. */
+ if (!tss->sp) {
+ char *stack;
+
+ stack = alloc_stack() + EXCEPTION_STACK_SIZE;
+ tss->sp = (unsigned long)stack;
+ tss->sp0 = (unsigned long)stack;
+ }
+
+ /* Set up exception handling TSS pointer in the GDT. */
+ __set_tss_desc(cpu, GDT_ENTRY_EXCEPTION_TSS + idx, tss);
+}
+#endif
+
void __init trap_init(void)
{
int i;
@@ -1205,7 +1252,9 @@ void __init trap_init(void)
set_trap_gate(5, &bounds);
set_trap_gate(6, &invalid_op);
set_trap_gate(7, &device_not_available);
- set_task_gate(8, GDT_ENTRY_DOUBLEFAULT_TSS);
+#ifdef DOUBLEFAULT_TSS
+ set_task_gate(8, GDT_ENTRY_EXCEPTION_TSS + DOUBLEFAULT_TSS);
+#endif
set_trap_gate(9, &coprocessor_segment_overrun);
set_trap_gate(10, &invalid_TSS);
set_trap_gate(11, &segment_not_present);
--- a/drivers/lguest/segments.c
+++ b/drivers/lguest/segments.c
@@ -50,7 +50,8 @@ static int ignored_gdt(unsigned int num)
return (num == GDT_ENTRY_TSS
|| num == GDT_ENTRY_LGUEST_CS
|| num == GDT_ENTRY_LGUEST_DS
- || num == GDT_ENTRY_DOUBLEFAULT_TSS);
+ || (num >= GDT_ENTRY_EXCEPTION_TSS
+ && num < GDT_ENTRY_EXCEPTION_TSS + N_EXCEPTION_TSS));
}
/*H:630 Once the Guest gave us new GDT entries, we fix them up a little. We
--- a/include/asm-x86/kdebug.h
+++ b/include/asm-x86/kdebug.h
@@ -20,6 +20,7 @@ enum die_val {
DIE_CALL,
DIE_NMI_IPI,
DIE_PAGE_FAULT,
+ DIE_DOUBLE_FAULT,
DIE_NMIUNKNOWN,
};
--- linux-2.6.26/include/asm-x86/processor.h 2008-07-13 23:51:29.000000000 +0200
+++ 2.6.26-i386-double-fault/include/asm-x86/processor.h 2008-06-25 14:52:11.000000000 +0200
@@ -128,7 +128,6 @@ struct cpuinfo_x86 {
extern struct cpuinfo_x86 boot_cpu_data;
extern struct cpuinfo_x86 new_cpu_data;
-extern struct tss_struct doublefault_tss;
extern __u32 cleared_cpu_caps[NCAPINTS];
#ifdef CONFIG_SMP
@@ -838,6 +837,12 @@ static inline void spin_lock_prefetch(co
.io_bitmap = { [0 ... IO_BITMAP_LONGS] = ~0 }, \
}
+#define EXCEPTION_STACK_ORDER 0
+#define EXCEPTION_STACK_SIZE (PAGE_SIZE << EXCEPTION_STACK_ORDER)
+
+void __cpuinit setup_exception_tss(unsigned int cpu, unsigned int idx,
+ void *(*alloc_stack)(void));
+
extern unsigned long thread_saved_pc(struct task_struct *tsk);
#define THREAD_SIZE_LONGS (THREAD_SIZE/sizeof(unsigned long))
--- linux-2.6.26/include/asm-x86/segment.h 2008-07-13 23:51:29.000000000 +0200
+++ 2.6.26-i386-double-fault/include/asm-x86/segment.h 2008-06-25 14:43:16.000000000 +0200
@@ -55,7 +55,7 @@
* 28 - unused
* 29 - unused
* 30 - unused
- * 31 - TSS for double fault handler
+ * 31+ TSSes for exception handlers
*/
#define GDT_ENTRY_TLS_MIN 6
#define GDT_ENTRY_TLS_MAX (GDT_ENTRY_TLS_MIN + GDT_ENTRY_TLS_ENTRIES - 1)
@@ -86,12 +86,19 @@
#define __KERNEL_PERCPU 0
#endif
-#define GDT_ENTRY_DOUBLEFAULT_TSS 31
+#define GDT_ENTRY_EXCEPTION_TSS 31
+#ifdef CONFIG_DOUBLEFAULT
+#define DOUBLEFAULT_TSS 0
+#define N_EXCEPTION_TSS 1
+#else
+#undef GDT_ENTRY_EXCEPTION_TSS
+#define N_EXCEPTION_TSS 0
+#endif
/*
- * The GDT has 32 entries
+ * The GDT has 31+ entries
*/
-#define GDT_ENTRIES 32
+#define GDT_ENTRIES (31 + N_EXCEPTION_TSS)
/* The PnP BIOS entries in the GDT */
#define GDT_ENTRY_PNPBIOS_CS32 (GDT_ENTRY_PNPBIOS_BASE + 0)
--
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