diff options
Diffstat (limited to 'gcc/ada/sigtramp.h')
| -rw-r--r-- | gcc/ada/sigtramp.h | 21 |
1 files changed, 15 insertions, 6 deletions
diff --git a/gcc/ada/sigtramp.h b/gcc/ada/sigtramp.h index f99bc20..3c28c8a 100644 --- a/gcc/ada/sigtramp.h +++ b/gcc/ada/sigtramp.h @@ -29,11 +29,19 @@ * * ****************************************************************************/ -/* On targets where this is implemented, we resort to a signal trampoline to - set up the DWARF Call Frame Information that lets unwinders walk through - the signal frame up into the interrupted user code. This file introduces - the relevant declarations. It should only be #included on targets that do - implement the signal trampoline. */ +/* On targets where this is useful, a signal handler trampoline is setup to + allow interposing handcrafted DWARF Call Frame Information that lets + unwinders walk through a signal frame up into the interrupted user code. + This file introduces the relevant declarations. + + For an OS family, in specific CPU configurations where kernel signal CFI + is known to be available, the trampoline may directly call the intended + handler without any intermediate CFI magic. + + sigtramp*.c offers a convenient spot for picking such alternatives, as + it allows testing for precise target predicates and is easily shared + by the tasking and non-tasking runtimes for a given OS (e.g. s-intman.adb + and init.c:__gnat_error_handler). */ #ifdef __cplusplus extern "C" { @@ -54,7 +62,8 @@ extern void __gnat_sigtramp (int signo, void *siginfo, void *sigcontext, __sigtramphandler_t * handler); /* The signal trampoline is to be called from an established signal handler. - It sets up the DWARF CFI and calls HANDLER (SIGNO, SIGINFO, SIGCONTEXT). + It calls HANDLER (SIGNO, SIGINFO, SIGCONTEXT) after setting up the DWARF + CFI if needed. The trampoline construct makes it so that the unwinder jumps over it + the signal handler + the kernel frame. For a typical backtrace from the raise |