x86/entry/entry_32.S

7  * Stack layout while running C code:
8  *	ptrace needs to have all registers on the stack.
123 	 * When we're here from kernel mode; the (exception) stack looks like:
171 	 * so any attempt to access the stack needs to use SS.  (except for
180 	 * middle doesn't scribble our stack.
233 	/* Switch to kernel stack if necessary */
325 	 * Setup and switch to ESPFIX stack
327 	 * We're returning to userspace with a 16 bit stack. The CPU will not
361  * entry-stack, it will overwrite the task-stack and everything we
362  * copied there. So allocate the stack-frame on the task-stack and
377 	/* Are we on the entry stack? Bail out if not! */
384 	/* Load stack pointer into %esi and %edi */
388 	/* Move %edi to the top of the entry stack */
392 	/* Load top of task-stack into %edi */
395 	/* Special case - entry from kernel mode via entry stack */
415 	 * Stack-frame contains 4 additional segment registers when
423 	/* Allocate frame on task-stack */
426 	/* Switch to task-stack */
430 	 * We are now on the task-stack and can safely copy over the
431 	 * stack-frame
443 	 * kernel-mode and %esp points to the entry-stack. When this
444 	 * happens we need to switch to the task-stack to run C code,
445 	 * but switch back to the entry-stack again when we approach
451 	 * When we switch to the task-stack here, we can't trust the
452 	 * contents of the entry-stack anymore, as the exception handler
454 	 * copy the complete entry-stack to the task-stack and set a
459 	 * entry-stack, so that the interrupted kernel code-path
460 	 * continues on the same stack it was interrupted with.
464 	 * %esi: Entry-Stack pointer (same as %esp)
465 	 * %edi: Top of the task stack
469 	/* Calculate number of bytes on the entry stack in %ecx */
472 	/* %ecx to the top of entry-stack */
476 	/* Number of bytes on the entry stack to %ecx */
479 	/* Mark stackframe as coming from entry stack */
493 	 * the stack-frame on task-stack and copy everything over
501  * Switch back from the kernel stack to the entry stack.
503  * The %esp register must point to pt_regs on the task stack. It will
504  * first calculate the size of the stack-frame to copy, depending on
506  * to copy the contents of the stack over to the entry stack.
509  * task-stack once we switched to the entry-stack. When an NMI happens
510  * while on the entry-stack, the NMI handler will switch back to the top
511  * of the task stack, overwriting our stack-frame we are about to copy.
512  * Therefore we switch the stack only after everything is copied over.
534 	/* Save future stack pointer in %ebx */
537 	/* Copy over the stack-frame */
543 	 * Switch to entry-stack - needs to happen after everything is
544 	 * copied because the NMI handler will overwrite the task-stack
545 	 * when on entry-stack
554  * path and have to switch back to the entry stack and/or user-cr3
562 	 * Test if we entered the kernel with the entry-stack. Most
571 	/* Clear marker from stack-frame */
574 	/* Copy the remaining task-stack contents to entry-stack */
578 	/* Bytes on the task-stack to ecx */
582 	/* Allocate stack-frame on entry-stack */
586 	 * Save future stack-pointer, we must not switch until the
588 	 * contents of the task-stack we are about to copy.
597 	/* Safe to switch to entry-stack now */
601 	 * We came from entry-stack and need to check if we also need to
607 	/* Clear marker from stack-frame */
620  * @has_error_code:	Hardware pushed error code on stack
645 	movl	PT_ORIG_EAX(%esp), %edx		/* get the vector from stack */
688 	/* switch stack */
698 	 * When switching from a shallower to a deeper call stack
729 	/* return address for the stack unwinder */
769  * SYSENTER does not save anything on the stack,
783  * ebp  user stack
788 	 * On entry-stack with all userspace-regs live - save and
799 	/* Stack empty again, switch to task stack */
809 	SAVE_ALL pt_regs_ax=$-ENOSYS	/* save rest, stack already switched */
844 	 * Setup entry stack - we keep the pointer in %eax and do the
848 	/* Load entry stack pointer and allocate frame for eflags/eax */
852 	/* Copy eflags and eax to entry stack */
869 	/* Switch to entry stack */
970 	 * The stack-frame here is the one that iret faulted on, so its a
987  * Switch back for ESPFIX stack to the normal zerobased stack
989  * We can't call C functions using the ESPFIX stack. This code reads
991  * normal stack and adjusts ESP with the matching offset.
998 	/* fixup the stack */
1012 	addl	%esp, %eax			/* the adjusted stack pointer */
1015 	lss	(%esp), %esp			/* switch to the normal stack segment */
1023 	/* see if on espfix stack */
1026 	/* switch to normal stack */
1033 	/* the function address is in %gs's slot on the stack */
1075 	 * The error code is on the stack, but the stack is otherwise
1116  * interrupted kernel code running on the SYSENTER stack.
1124 	 * after we've switched to the entry stack.
1139 	/* Are we currently on the SYSENTER stack? */
1146 	/* Not on SYSENTER stack. */
1152 	 * We're on the SYSENTER stack.  Switch off.  No one (not even debug)
1153 	 * is using the thread stack right now, so it's safe for us to use it.
1209 	lss	(1+5+6)*4(%esp), %esp			# back to espfix stack