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| -rw-r--r-- | glibc/startup.mdwn | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/glibc/startup.mdwn b/glibc/startup.mdwn index ac7cdde6..9e1137f5 100644 --- a/glibc/startup.mdwn +++ b/glibc/startup.mdwn @@ -21,6 +21,44 @@ is quite hairy on GNU Hurd systems. * [[!message-id "871xc9qv6y.wl@ulysses.g10code.de"]] +# How libc startup in a process works + +## Statically-linked program + + * The ELF headers points program start at `_start`. + * `_start` (sysdeps/mach/hurd/i386/static-start.S) calls `_hurd_stack_setup` + * `_hurd_stack_setup` (sysdeps/mach/hurd/i386/init-first.c) calls `first_init` which calls `__mach_init` to initialize enough to run RPCs, then runs the `_hurd_preinit_hook` hooks, which initialize global variables of libc. + * `_hurd_stack_setup` (sysdeps/mach/hurd/i386/init-first.c) calls `_hurd_startup`. + * `_hurd_startup` (hurd/hurdstartup.c) gets hurdish information from servers and calls its `main` parameter. + * the `main` parameter was actually `doinit`, which mangles the stack and calls `doinit1` which calls `init`. + * `init` sets threadvars, tries to initialize threads (and perhaps switches to the new stack) and gets to call `init1`. + * `init1` checks the new stack, calls `_hurd_init` (hurd/hurdinit.c) + * `_hurd_init` initializes initial ports, runs the `_hurd_subinit` hooks (`init_dtable` hurd/dtable.c notably initializes the FD table and the `_hurd_fd_subinit` hooks, which notably checks `std*`). + * We are back to `_start`, which jumps to `_start1` which is the normal libc startup which calls `__libc_start_main` + * `__libc_start_main` (actually called `LIBC_START_MAIN` in csu/libc-start.c) initializes libc, tls, libpthread, atexit, an initialization function given as parameter, then calls application's `main`, then `exit`. + +## dynamically-linked program + + * dl.so ELF headers point its start at `_start`. + * `_start` (sysdeps/i386/dl-machine.h) calls `_dl_start`. + * `_dl_start` (elf/rtld.c) initializes `bootstrap_map`, calls `_dl_start_final` + * `_dl_start_final` calls `_dl_sysdep_start`. + * `_dl_sysdep_start` calls `__mach_init` to initialize enough to run RPCs, then calls `_hurd_startup`. + * `_hurd_startup` (hurd/hurdstartup.c) gets hurdish information from servers and calls its `main` parameter. + * the `main` parameter was actually `go`, which calls `dl_main`. + * `dl_main` (elf/rtld.c) interprets ld.so parameters, loads the binary and libraries, calls `_dl_allocate_tls_init`. + * we are back to `go`, which branches to `_dl_start_user`. + * `_dl_start_user` (./sysdeps/i386/dl-machine.h) runs `RTLD_START_SPECIAL_INIT` (sysdeps/mach/hurd/i386/dl-machine.h) which calls `_dl_init_first`. + * `_dl_init_first` calls `first_init` which calls `__mach_init` to initialize enough to run RPCs, then runs the `_hurd_preinit_hook` hooks, which initialize global variables of libc. + * `_dl_init_first` calls `init`. + * `init` sets threadvars, tries to initialize threads (and perhaps switches to the new stack) and gets to call `init1`. + * `init1` checks the new stack, calls `_hurd_init` (hurd/hurdinit.c) + * `_hurd_init` initializes initial ports, runs the `_hurd_subinit` hooks (`init_dtable` hurd/dtable.c notably initializes the FD table and the `_hurd_fd_subinit` hooks, which notably checks `std*`). + * we are back to `_dl_start_user`, which calls `_dl_init` (elf/dl-init.c) which calls application initializers. + * `_dl_start_user` jumps to the application's entry point, `_start` + * `_start` (sysdeps/i386/start.S) calls `__libc_start_main` + * `__libc_start_main` (actually called `LIBC_START_MAIN` in csu/libc-start.c) initializes libc, tls, libpthread, atexit, an initialization function given as parameter, then calls application's `main`, then `exit`. + # IRC, freenode, #hurd, 2013-12-31 <youpi> braunr: btw, after patching glibc and trying installing it, do you |