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diff --git a/nuttx/syscall/README.txt b/nuttx/syscall/README.txt deleted file mode 100644 index ed5e6081d..000000000 --- a/nuttx/syscall/README.txt +++ /dev/null @@ -1,147 +0,0 @@ -syscall/README.txt -================== - -This directory supports a syscall layer from communication between a -monolithic, kernel-mode NuttX kernel and a separately built, user-mode -application set. - -With most MCUs, NuttX is built as a flat, single executable image -containing the NuttX RTOS along with all application code. The RTOS code -and the application run in the same address space and at the same kernel- -mode privileges. In order to exploit security features of certain -processors, an alternative build model is also supported: NuttX can -be built separately as a monolithic, kernel-mode module and the applications -can be added as a separately built, user-mode module. - -The syscall layer provided in this directory serves as the communication -layer from the user-mode application into the kernel-mode RTOS. The -switch from user-mode to kernel-mode is accomplished using software -interrupts (SWIs). SWIs are implemented differently and named differently -by different manufacturers but all work essentially the same: A special -instruction is executed in user-mode that causes a software generated -interrupt. The software generated interrupt is caught within the kernel -and handle in kernel-mode. - -Header Files -============ - -include/syscall.h - - This header file supports general access to SWI facilities. It is simply - a wrapper file that includes include/sys/syscall.h and - include/arch/syscall.h. - -include/sys/syscall.h - - The SWIs received by the kernel are distinguish by a code that identifies - how to process the SWI. This header file defines all such codes understood - by the NuttX kernel. - -include/arch/syscall.h (or arch/<cpu>/include/syscall.h) - - This header file is provided by the platform-specific logic and declares - (or defines) the mechanism for providing software interrupts on this - platform. The following functions must be declared (or defined) in this - header file: - - - SWI with SYS_ call number and one parameter - - uintptr_t sys_call0(unsigned int nbr); - - - SWI with SYS_ call number and one parameter - - uintptr_t sys_call1(unsigned int nbr, uintptr_t parm1); - - - SWI with SYS_ call number and two parameters - - uintptr_t sys_call2(unsigned int nbr, uintptr_t parm1, uintptr_t parm2); - - - SWI with SYS_ call number and three parameters - - uintptr_t sys_call3(unsigned int nbr, uintptr_t parm1, - uintptr_t parm2, uintptr_t parm3); - - - SWI with SYS_ call number and four parameters - - uintptr_t sys_call4(unsigned int nbr, uintptr_t parm1, uintptr_t parm2, - uintptr_t parm3, uintptr_t parm4); - - - SWI with SYS_ call number and five parameters - - uintptr_t sys_call5(unsigned int nbr, uintptr_t parm1, uintptr_t parm2, - uintptr_t parm3, uintptr_t parm4, uintptr_t parm5); - - - SWI with SYS_ call number and six parameters - - uintptr_t sys_call6(unsigned int nbr, uintptr_t parm1, uintptr_t parm2, - uintptr_t parm3, uintptr_t parm4, uintptr_t parm5, - uintptr_t parm6); -Syscall Database -================ - -Sycall information is maintained in a database. That "database" is -implemented as a simple comma-separated-value file, syscall.csv. Most -spreadsheets programs will accept this format and can be used to maintain -the syscall database. - -The format of the CSV file for each line is: - - Field 1: Function name - Field 2: The header file that contains the function prototype - Field 3: Condition for compilation - Field 4: The type of function return value. - Field 5 - N+5: The type of each of the N formal parameters of the function - -Each type field has a format as follows: - - type name: - For all simpler types - formal type | actual type: - For array types where the form of the formal (eg. int parm[2]) - differs from the type of actual passed parameter (eg. int*). This - is necessary because you cannot do simple casts to array types. - formal type | union member actual type | union member fieldname: - A similar situation exists for unions. For example, the formal - parameter type union sigval -- You cannot cast a uintptr_t to - a union sigval, but you can cast to the type of one of the union - member types when passing the actual paramter. Similarly, we - cannot cast a union sigval to a uinptr_t either. Rather, we need - to cast a specific union member fieldname to uintptr_t. - -NOTE: This CSV file is used both to support the generate of trap information, -but also for the generation of symbol tables. See nuttx/tools/README.txt -and nuttx/lib/README.txt for further information. - -Auto-Generated Files -==================== - -Stubs and proxies for the sycalls are automatically generated from this CSV -database. Here the following definition is used: - - Proxy - A tiny bit of code that executes in the user space. A proxy - has exactly the same function prototype as does the "real" function - for which it proxies. However, it only serves to map the function - call into a syscall, marshaling all of the system call parameters - as necessary. - - Stub - Another tiny bit of code that executes within the NuttX kernel - that is used to map a software interrupt received by the kernel to - a kernel function call. The stubs receive the marshaled system - call data, and perform the actually kernel function call (in - kernel-mode) on behalf of the proxy function. - -Sub-Directories -=============== - - stubs - Autogenerated stub files are placed in this directory. - proxies - Autogenerated proxy files are placed in this directory. - -mksyscall -========= - - mksyscall is C program that is used used during the initial NuttX build - by the logic in the top-level syscall/ directory. Information about the - stubs and proxies is maintained in a comma separated value (CSV) file - in the syscall/ directory. The mksyscall program will accept this CVS - file as input and generate all of the required proxy or stub files as - output. See tools/README.txt for additional information. |