1 Bionic comes with a processed set of all of the uapi Linux kernel headers that 2 can safely be included by userland applications and libraries. 3 4 These clean headers are automatically generated by several scripts located 5 in the 'bionic/kernel/tools' directory. The tools process the original 6 unmodified kernel headers in order to get rid of many annoying 7 declarations and constructs that usually result in compilation failure. 8 9 The 'clean headers' only contain type and macro definitions, with the 10 exception of a couple static inline functions used for performance 11 reason (e.g. optimized CPU-specific byte-swapping routines). 12 13 They can be included from C++, or when compiling code in strict ANSI mode. 14 They can be also included before or after any Bionic C library header. 15 16 Description of the directories involved in generating the parsed kernel headers: 17 18 * 'external/kernel-headers/original/' 19 Contains the uapi kernel headers found in the android kernel. Note this 20 also includes the header files that are generated by building the kernel 21 sources. 22 23 * 'bionic/libc/kernel/uapi' 24 Contains the cleaned kernel headers and mirrors the directory structure 25 in 'external/kernel-headers/original/uapi/'. 26 27 * 'bionic/libc/kernel/tools' 28 Contains various Python and shell scripts used to get and re-generate 29 the headers. 30 31 The tools to get/parse the headers: 32 33 * tools/generate_uapi_headers.sh 34 Checks out the android kernel and generates all uapi header files. 35 copies all the changed files into external/kernel-headers. 36 37 * tools/clean_header.py 38 Prints the clean version of a given kernel header. With the -u option, 39 this will also update the corresponding clean header file if its 40 content has changed. You can also process more than one file with -u. 41 42 * tools/update_all.py 43 Automatically update all clean headers from the content of 44 'external/kernel-headers/original'. 45 46 47 HOW TO UPDATE THE HEADERS WHEN NEEDED: 48 ====================================== 49 50 IMPORTANT IMPORTANT: 51 52 WHEN UPDATING THE HEADERS, ALWAYS CHECK THAT THE NEW CLEAN HEADERS DO 53 NOT BREAK THE KERNEL <-> USER ABI, FOR EXAMPLE BY CHANGING THE SIZE 54 OF A GIVEN TYPE. THIS TASK CANNOT BE EASILY AUTOMATED AT THE MOMENT 55 56 Grab the latest headers from the android kernel by running this command: 57 58 bionic/libc/kernel/tools/generate_uapi_headers.sh --download-kernel 59 60 Next, run this command to copy the parsed files to bionic/libc/kernel/uapi: 61 62 bionic/libc/kernel/tools/update_all.py 63 64 Finally, run this command to regenerate the syscalls list: 65 66 bionic/libc/tools/gensyscalls.py 67 68 After this, you will need to build/test the tree to make sure that these 69 changes do not introduce any errors. 70
