diff options
Diffstat (limited to 'Documentation/x86_64/kernel-stacks')
-rw-r--r-- | Documentation/x86_64/kernel-stacks | 26 |
1 files changed, 13 insertions, 13 deletions
diff --git a/Documentation/x86_64/kernel-stacks b/Documentation/x86_64/kernel-stacks index bddfddd466ab..5ad65d51fb95 100644 --- a/Documentation/x86_64/kernel-stacks +++ b/Documentation/x86_64/kernel-stacks | |||
@@ -9,9 +9,9 @@ zombie. While the thread is in user space the kernel stack is empty | |||
9 | except for the thread_info structure at the bottom. | 9 | except for the thread_info structure at the bottom. |
10 | 10 | ||
11 | In addition to the per thread stacks, there are specialized stacks | 11 | In addition to the per thread stacks, there are specialized stacks |
12 | associated with each cpu. These stacks are only used while the kernel | 12 | associated with each CPU. These stacks are only used while the kernel |
13 | is in control on that cpu, when a cpu returns to user space the | 13 | is in control on that CPU; when a CPU returns to user space the |
14 | specialized stacks contain no useful data. The main cpu stacks is | 14 | specialized stacks contain no useful data. The main CPU stacks are: |
15 | 15 | ||
16 | * Interrupt stack. IRQSTACKSIZE | 16 | * Interrupt stack. IRQSTACKSIZE |
17 | 17 | ||
@@ -32,17 +32,17 @@ x86_64 also has a feature which is not available on i386, the ability | |||
32 | to automatically switch to a new stack for designated events such as | 32 | to automatically switch to a new stack for designated events such as |
33 | double fault or NMI, which makes it easier to handle these unusual | 33 | double fault or NMI, which makes it easier to handle these unusual |
34 | events on x86_64. This feature is called the Interrupt Stack Table | 34 | events on x86_64. This feature is called the Interrupt Stack Table |
35 | (IST). There can be up to 7 IST entries per cpu. The IST code is an | 35 | (IST). There can be up to 7 IST entries per CPU. The IST code is an |
36 | index into the Task State Segment (TSS), the IST entries in the TSS | 36 | index into the Task State Segment (TSS). The IST entries in the TSS |
37 | point to dedicated stacks, each stack can be a different size. | 37 | point to dedicated stacks; each stack can be a different size. |
38 | 38 | ||
39 | An IST is selected by an non-zero value in the IST field of an | 39 | An IST is selected by a non-zero value in the IST field of an |
40 | interrupt-gate descriptor. When an interrupt occurs and the hardware | 40 | interrupt-gate descriptor. When an interrupt occurs and the hardware |
41 | loads such a descriptor, the hardware automatically sets the new stack | 41 | loads such a descriptor, the hardware automatically sets the new stack |
42 | pointer based on the IST value, then invokes the interrupt handler. If | 42 | pointer based on the IST value, then invokes the interrupt handler. If |
43 | software wants to allow nested IST interrupts then the handler must | 43 | software wants to allow nested IST interrupts then the handler must |
44 | adjust the IST values on entry to and exit from the interrupt handler. | 44 | adjust the IST values on entry to and exit from the interrupt handler. |
45 | (this is occasionally done, e.g. for debug exceptions) | 45 | (This is occasionally done, e.g. for debug exceptions.) |
46 | 46 | ||
47 | Events with different IST codes (i.e. with different stacks) can be | 47 | Events with different IST codes (i.e. with different stacks) can be |
48 | nested. For example, a debug interrupt can safely be interrupted by an | 48 | nested. For example, a debug interrupt can safely be interrupted by an |
@@ -58,17 +58,17 @@ The currently assigned IST stacks are :- | |||
58 | 58 | ||
59 | Used for interrupt 12 - Stack Fault Exception (#SS). | 59 | Used for interrupt 12 - Stack Fault Exception (#SS). |
60 | 60 | ||
61 | This allows to recover from invalid stack segments. Rarely | 61 | This allows the CPU to recover from invalid stack segments. Rarely |
62 | happens. | 62 | happens. |
63 | 63 | ||
64 | * DOUBLEFAULT_STACK. EXCEPTION_STKSZ (PAGE_SIZE). | 64 | * DOUBLEFAULT_STACK. EXCEPTION_STKSZ (PAGE_SIZE). |
65 | 65 | ||
66 | Used for interrupt 8 - Double Fault Exception (#DF). | 66 | Used for interrupt 8 - Double Fault Exception (#DF). |
67 | 67 | ||
68 | Invoked when handling a exception causes another exception. Happens | 68 | Invoked when handling one exception causes another exception. Happens |
69 | when the kernel is very confused (e.g. kernel stack pointer corrupt) | 69 | when the kernel is very confused (e.g. kernel stack pointer corrupt). |
70 | Using a separate stack allows to recover from it well enough in many | 70 | Using a separate stack allows the kernel to recover from it well enough |
71 | cases to still output an oops. | 71 | in many cases to still output an oops. |
72 | 72 | ||
73 | * NMI_STACK. EXCEPTION_STKSZ (PAGE_SIZE). | 73 | * NMI_STACK. EXCEPTION_STKSZ (PAGE_SIZE). |
74 | 74 | ||