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 bddfddd466a..5ad65d51fb9 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 except for the thread_info structure at the bottom. In addition to the per thread stacks, there are specialized stacks -associated with each cpu. These stacks are only used while the kernel -is in control on that cpu, when a cpu returns to user space the -specialized stacks contain no useful data. The main cpu stacks is +associated with each CPU. These stacks are only used while the kernel +is in control on that CPU; when a CPU returns to user space the +specialized stacks contain no useful data. The main CPU stacks are: * Interrupt stack. IRQSTACKSIZE @@ -32,17 +32,17 @@ x86_64 also has a feature which is not available on i386, the ability to automatically switch to a new stack for designated events such as double fault or NMI, which makes it easier to handle these unusual events on x86_64. This feature is called the Interrupt Stack Table -(IST). There can be up to 7 IST entries per cpu. The IST code is an -index into the Task State Segment (TSS), the IST entries in the TSS -point to dedicated stacks, each stack can be a different size. +(IST). There can be up to 7 IST entries per CPU. The IST code is an +index into the Task State Segment (TSS). The IST entries in the TSS +point to dedicated stacks; each stack can be a different size. -An IST is selected by an non-zero value in the IST field of an +An IST is selected by a non-zero value in the IST field of an interrupt-gate descriptor. When an interrupt occurs and the hardware loads such a descriptor, the hardware automatically sets the new stack pointer based on the IST value, then invokes the interrupt handler. If software wants to allow nested IST interrupts then the handler must adjust the IST values on entry to and exit from the interrupt handler. -(this is occasionally done, e.g. for debug exceptions) +(This is occasionally done, e.g. for debug exceptions.) Events with different IST codes (i.e. with different stacks) can be nested. For example, a debug interrupt can safely be interrupted by an @@ -58,17 +58,17 @@ The currently assigned IST stacks are :- Used for interrupt 12 - Stack Fault Exception (#SS). - This allows to recover from invalid stack segments. Rarely + This allows the CPU to recover from invalid stack segments. Rarely happens. * DOUBLEFAULT_STACK. EXCEPTION_STKSZ (PAGE_SIZE). Used for interrupt 8 - Double Fault Exception (#DF). - Invoked when handling a exception causes another exception. Happens - when the kernel is very confused (e.g. kernel stack pointer corrupt) - Using a separate stack allows to recover from it well enough in many - cases to still output an oops. + Invoked when handling one exception causes another exception. Happens + when the kernel is very confused (e.g. kernel stack pointer corrupt). + Using a separate stack allows the kernel to recover from it well enough + in many cases to still output an oops. * NMI_STACK. EXCEPTION_STKSZ (PAGE_SIZE). |