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authorThomas Schwinge <thomas@codesourcery.com>2018-05-09 22:46:31 +0200
committerThomas Schwinge <thomas@codesourcery.com>2018-05-09 22:46:31 +0200
commitdec7cfc3be51acb52bf6dbba4cd0c2be35786d0a (patch)
treea9e3ee41086dceff53369679ab2d7e23b3ac2843 /glibc
parent3581c9cf04f239b8fc6dc0bfa77a818416f70e7f (diff)
parent96dba7ef358153dd1a608ab45f52226d08d62e3c (diff)
Merge commit '96dba7ef358153dd1a608ab45f52226d08d62e3c'
As part of the merge, fix some typos, adjust copyright headers, and apply a few more minor changes.
Diffstat (limited to 'glibc')
-rw-r--r--glibc/startup.mdwn51
1 files changed, 50 insertions, 1 deletions
diff --git a/glibc/startup.mdwn b/glibc/startup.mdwn
index ac7cdde..9a7a3de 100644
--- a/glibc/startup.mdwn
+++ b/glibc/startup.mdwn
@@ -1,4 +1,4 @@
-[[!meta copyright="Copyright © 2011, 2014, 2016 Free Software Foundation,
+[[!meta copyright="Copyright © 2011, 2014, 2016, 2018 Free Software Foundation,
Inc."]]
[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
@@ -21,6 +21,55 @@ 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` (in sysdeps/mach/hurd/i386/init-first.c), 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` gets the Hurd block, calls `_hurd_init` on it
+ * `_hurd_init` (hurd/hurdinit.c) initializes initial ports, starts the signal thread, 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
+ * `__libc_start_main` calls initialization function given as parameter `__libc_csu_init`,
+ * `__libc_csu_init` (csu/elf-init.c) calls `preinit_array_start` functions
+ * `__libc_csu_init` calls `_init`
+ * `_init` (sysdeps/i386/crti.S) calls `PREINIT_FUNCTION`, (actually libpthread on Linux, `__gmon_start__` on hurd)
+ * back to `__libc_csu_init` calls `init_array_start` functions
+ * back to `__libc_start_main`, it calls 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` (sysdeps/mach/hurd/dl-sysdep.c) 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` inside `_dl_sysdep_start`, 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` (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.
+ * `_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` gets the Hurd block, calls `_hurd_init` on it
+ * `_hurd_init` (hurd/hurdinit.c) initializes initial ports, starts the signal thread, 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, atexit,
+ * `__libc_start_main` calls initialization function given as parameter `__libc_csu_init`,
+ * `__libc_csu_init` (csu/elf-init.c) calls `_init`
+ * `_init` (sysdeps/i386/crti.S) calls `PREINIT_FUNCTION`, (actually libpthread on Linux, `__gmon_start__` on hurd)
+ * back to `__libc_csu_init` calls `init_array_start` functions
+ * back to `__libc_start_main`, it calls application's `main`, then `exit`.
+
# IRC, freenode, #hurd, 2013-12-31
<youpi> braunr: btw, after patching glibc and trying installing it, do you