58 | | It is located in the lower part of the virtual space, and starts a address 0. It contains the three vsegs ''kentry'', ''args'', ''envs'', whose sizes are defined by [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/kernel_config.h#L300 specific configuration parameters]. |
59 | | * The ''kentry'' vseg (CODE type) contains the HAL specific code that must be executed to enter/exit the kernel from user space (in case of interrupts, exceptions, or syscalls). It also contains the HAL specific code for context switches. For some architectures (namely the TSAR 32 bits architectures), this vseg must be identity mapped. |
| 63 | |
| 64 | It contains the two ''args'' and ''envs'' vsegs, whose sizes are defined by [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/kernel_config. specific configuration parameters]. |
67 | | It is located on top of the '''elf''' zone, and starts at the address defined by the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/kernel_config.h#L297 CONFIG_VMM_HEAP_BASE] parameter. It contains all vsegs dynamically allocated / released by the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/syscalls/sys_mmap.c#L38 mmap()] / [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/syscalls/sys_munmap.c#L37 munmap()] system calls (i.e. FILE / ANON / REMOTE types). The VMM implements a specific MMAP allocator for this zone, implementing the ''buddy'' algorithm. The mmap( FILE ) syscall maps directly a file in user space. The user level ''malloc'' library uses the mmap( ANON ) syscall to allocate virtual memory from the heap and map it in the same cluster as the calling thread. Besides the standard malloc() function, this library implements a non-standard [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/libs/libalmosmkh/almosmkh.c#L581 remote_malloc()] function, that uses the mmap( REMOTE ) syscall to dynamically allocate virtual memory from the heap, and map it to a remote physical cluster. |
| 74 | |
| 75 | It contains all vsegs dynamically allocated / released by the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/syscalls/sys_mmap.c mmap()] / [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/syscalls/sys_munmap.c munmap()] system calls (i.e. FILE / ANON / REMOTE types). |
| 76 | It is located on top of the '''elf''' zone, and starts at the address defined by the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/kernel_config.h CONFIG_VMM_HEAP_BASE] parameter. The VMM defines a specific MMAP allocator for this zone, implementing the ''buddy'' algorithm. The mmap( FILE ) syscall maps directly a file in user space. The user level ''malloc'' library uses the mmap( ANON ) syscall to allocate virtual memory from the heap and map it in the same cluster as the calling thread. Besides the standard malloc() function, this library implements a non-standard [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/libs/libalmosmkh/almosmkh.c remote_malloc()] function, that uses the mmap( REMOTE ) syscall to dynamically allocate virtual memory from the heap, and map it to a remote physical cluster. |
70 | | It is located on top of the '''mmap''' zone and starts at the address defined by the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/kernel_config.h#L298 CONFIG_VMM_STACK_BASE] parameter. It contains an array of fixed size slots, and each slot contains one ''stack'' vseg. The size of a slot is defined by the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/kernel_config.h#L303 CONFIG_VMM_STACK_SIZE]. In each slot, the first page is not mapped, in order to detect stack overflows. As threads are dynamically created and destroyed, the VMM implements a specific STACK allocator for this zone, using a bitmap vector. As the ''stack'' vsegs are private (the same virtual address can have different mappings, depending on the cluster) the number of slots in the '''stack''' zone actually defines the max number of threads for given process in a given cluster. |
| 79 | |
| 80 | It is located on top of the '''mmap''' zone and starts at the address defined by the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/kernel_config.h CONFIG_VMM_STACK_BASE] parameter. It contains an array of fixed size slots, and each slot contains one ''stack'' vseg. The size of a slot is defined by the [https://www-soc.lip6.fr/trac/almos-mkh/browser/trunk/kernel/kernel_config.h CONFIG_VMM_STACK_SIZE]. In each slot, the first page is not mapped, in order to detect stack overflows. As threads are dynamically created and destroyed, the VMM implements a specific STACK allocator for this zone, using a bitmap vector. As the ''stack'' vsegs are private (the same virtual address can have different mappings, depending on the cluster) the number of slots in the '''stack''' zone actually defines the max number of threads for given process in a given cluster. |