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…nux-2.6 * 'for-linus' of git://one.firstfloor.org/home/andi/git/linux-2.6: (225 commits) [PATCH] Don't set calgary iommu as default y [PATCH] i386/x86-64: New Intel feature flags [PATCH] x86: Add a cumulative thermal throttle event counter. [PATCH] i386: Make the jiffies compares use the 64bit safe macros. [PATCH] x86: Refactor thermal throttle processing [PATCH] Add 64bit jiffies compares (for use with get_jiffies_64) [PATCH] Fix unwinder warning in traps.c [PATCH] x86: Allow disabling early pci scans with pci=noearly or disallowing conf1 [PATCH] x86: Move direct PCI scanning functions out of line [PATCH] i386/x86-64: Make all early PCI scans dependent on CONFIG_PCI [PATCH] Don't leak NT bit into next task [PATCH] i386/x86-64: Work around gcc bug with noreturn functions in unwinder [PATCH] Fix some broken white space in ia32_signal.c [PATCH] Initialize argument registers for 32bit signal handlers. [PATCH] Remove all traces of signal number conversion [PATCH] Don't synchronize time reading on single core AMD systems [PATCH] Remove outdated comment in x86-64 mmconfig code [PATCH] Use string instructions for Core2 copy/clear [PATCH] x86: - restore i8259A eoi status on resume [PATCH] i386: Split multi-line printk in oops output. ...
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@@ -358,7 +358,8 @@ Here is a list of some of the different kernel trees available: | |
quilt trees: | ||
- USB, PCI, Driver Core, and I2C, Greg Kroah-Hartman <[email protected]> | ||
kernel.org/pub/linux/kernel/people/gregkh/gregkh-2.6/ | ||
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- x86-64, partly i386, Andi Kleen <[email protected]> | ||
ftp.firstfloor.org:/pub/ak/x86_64/quilt/ | ||
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Bug Reporting | ||
------------- | ||
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Most of the text from Keith Owens, hacked by AK | ||
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x86_64 page size (PAGE_SIZE) is 4K. | ||
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Like all other architectures, x86_64 has a kernel stack for every | ||
active thread. These thread stacks are THREAD_SIZE (2*PAGE_SIZE) big. | ||
These stacks contain useful data as long as a thread is alive or a | ||
zombie. While the thread is in user space the kernel stack is empty | ||
except for the thread_info structure at the bottom. | ||
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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 | ||
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* Interrupt stack. IRQSTACKSIZE | ||
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Used for external hardware interrupts. If this is the first external | ||
hardware interrupt (i.e. not a nested hardware interrupt) then the | ||
kernel switches from the current task to the interrupt stack. Like | ||
the split thread and interrupt stacks on i386 (with CONFIG_4KSTACKS), | ||
this gives more room for kernel interrupt processing without having | ||
to increase the size of every per thread stack. | ||
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The interrupt stack is also used when processing a softirq. | ||
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Switching to the kernel interrupt stack is done by software based on a | ||
per CPU interrupt nest counter. This is needed because x86-64 "IST" | ||
hardware stacks cannot nest without races. | ||
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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. | ||
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An IST is selected by an 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) | ||
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Events with different IST codes (i.e. with different stacks) can be | ||
nested. For example, a debug interrupt can safely be interrupted by an | ||
NMI. arch/x86_64/kernel/entry.S::paranoidentry adjusts the stack | ||
pointers on entry to and exit from all IST events, in theory allowing | ||
IST events with the same code to be nested. However in most cases, the | ||
stack size allocated to an IST assumes no nesting for the same code. | ||
If that assumption is ever broken then the stacks will become corrupt. | ||
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The currently assigned IST stacks are :- | ||
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* STACKFAULT_STACK. EXCEPTION_STKSZ (PAGE_SIZE). | ||
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Used for interrupt 12 - Stack Fault Exception (#SS). | ||
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This allows to recover from invalid stack segments. Rarely | ||
happens. | ||
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* DOUBLEFAULT_STACK. EXCEPTION_STKSZ (PAGE_SIZE). | ||
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Used for interrupt 8 - Double Fault Exception (#DF). | ||
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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. | ||
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* NMI_STACK. EXCEPTION_STKSZ (PAGE_SIZE). | ||
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Used for non-maskable interrupts (NMI). | ||
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NMI can be delivered at any time, including when the kernel is in the | ||
middle of switching stacks. Using IST for NMI events avoids making | ||
assumptions about the previous state of the kernel stack. | ||
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* DEBUG_STACK. DEBUG_STKSZ | ||
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Used for hardware debug interrupts (interrupt 1) and for software | ||
debug interrupts (INT3). | ||
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When debugging a kernel, debug interrupts (both hardware and | ||
software) can occur at any time. Using IST for these interrupts | ||
avoids making assumptions about the previous state of the kernel | ||
stack. | ||
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* MCE_STACK. EXCEPTION_STKSZ (PAGE_SIZE). | ||
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Used for interrupt 18 - Machine Check Exception (#MC). | ||
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MCE can be delivered at any time, including when the kernel is in the | ||
middle of switching stacks. Using IST for MCE events avoids making | ||
assumptions about the previous state of the kernel stack. | ||
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For more details see the Intel IA32 or AMD AMD64 architecture manuals. |
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