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8076185: Provide SafeFetchX implementation for zero

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Implement SafeFetchX for zero using setjmp/longjmp and Posix TLS

Reviewed-by: sgehwolf, dholmes
This commit is contained in:
Thomas Stuefe 2015-03-31 05:30:36 -04:00 • committed by David Holmes
parent 38c3337610
commit 1afbc04d56
4 changed files with 79 additions and 8 deletions
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53
hotspot/src/cpu/zero/vm/stubGenerator_zero.cpp
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@ -45,6 +45,18 @@
#include "opto/runtime.hpp"
#endif
// For SafeFetch we need POSIX tls and setjmp
#include <setjmp.h>
#include <pthread.h>
static pthread_key_t g_jmpbuf_key;
// return the currently active jump buffer for this thread
// - if there is any, NULL otherwise. Called from
// zero signal handlers.
extern sigjmp_buf* get_jmp_buf_for_continuation() {
return (sigjmp_buf*) pthread_getspecific(g_jmpbuf_key);
}
// Declaration and definition of StubGenerator (no .hpp file).
// For a more detailed description of the stub routine structure
// see the comment in stubRoutines.hpp
@ -176,17 +188,55 @@ class StubGenerator: public StubCodeGenerator {
StubRoutines::_oop_arraycopy;
}
// NYI: SafeFetch for Zero isn't actually safe.
static int SafeFetch32(int *adr, int errValue) {
// set up a jump buffer; anchor the pointer to the jump buffer in tls; then
// do the pointer access. If pointer is invalid, we crash; in signal
// handler, we retrieve pointer to jmp buffer from tls, and jump back.
//
// Note: the jump buffer itself - which can get pretty large depending on
// the architecture - lives on the stack and that is fine, because we will
// not rewind the stack: either we crash, in which case signal handler
// frame is below us, or we don't crash, in which case it does not matter.
sigjmp_buf jb;
if (sigsetjmp(jb, 1)) {
// we crashed. clean up tls and return default value.
pthread_setspecific(g_jmpbuf_key, NULL);
return errValue;
} else {
// preparation phase
pthread_setspecific(g_jmpbuf_key, &jb);
}
int value = errValue;
value = *adr;
// all went well. clean tls.
pthread_setspecific(g_jmpbuf_key, NULL);
return value;
}
static intptr_t SafeFetchN(intptr_t *adr, intptr_t errValue) {
sigjmp_buf jb;
if (sigsetjmp(jb, 1)) {
// we crashed. clean up tls and return default value.
pthread_setspecific(g_jmpbuf_key, NULL);
return errValue;
} else {
// preparation phase
pthread_setspecific(g_jmpbuf_key, &jb);
}
intptr_t value = errValue;
value = *adr;
// all went well. clean tls.
pthread_setspecific(g_jmpbuf_key, NULL);
return value;
}
void generate_initial() {
@ -241,6 +291,7 @@ class StubGenerator: public StubCodeGenerator {
generate_arraycopy_stubs();
// Safefetch stubs.
pthread_key_create(&g_jmpbuf_key, NULL);
StubRoutines::_safefetch32_entry = CAST_FROM_FN_PTR(address, StubGenerator::SafeFetch32);
StubRoutines::_safefetch32_fault_pc = NULL;
StubRoutines::_safefetch32_continuation_pc = NULL;