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JIT: fix potential problem in transition to 64-bit jumps

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On x86_64, the JIT compiler initially generates code with 32-bit
jumps, but it switches to 64-bit jumps when so much code is allocated
that it gets spaced out enough. That transition could happen during a
recursive call to the JIT compiler or while one place is in the JIT
and other installs a shared code pointer, in which case a bad jump
could be generated. This problem is unlikely to happen, but it looks
possible.
This commit is contained in:
Matthew Flatt 2014-05-30 06:06:35 +01:00
parent a7d91f0f9c
commit c0ec9702e8
4 changed files with 24 additions and 0 deletions
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2
racket/src/racket/src/jit.c
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@ -3320,6 +3320,7 @@ static int do_generate_closure(mz_jit_state *jitter, void *_data)
shared_arity_code = jit_adjust_ip(shared_arity_code);
sjc.shared_arity_check[num_params][has_rest][is_method] = shared_arity_code;
}
CHECK_NESTED_GENERATE();
arity_code = jit_get_ip();
@ -3334,6 +3335,7 @@ static int do_generate_closure(mz_jit_state *jitter, void *_data)
((void **)retain_code)[1] = arity_code;
#endif
arity_code = jit_adjust_ip(arity_code);
CHECK_NESTED_GENERATE();
}
/* A tail call starts here. Caller must ensure that the stack is big

10
racket/src/racket/src/jit.h
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@ -1324,6 +1324,16 @@ static int past_limit(mz_jit_state *jitter, const char *file, int line)
}
#endif
/* Use CHECK_NESTED_GENERATE() after a nested call to scheme_generate_one()
or after getting a shared code pointer that may be generated by another
place: */
#ifdef SET_DEFAULT_LONG_JUMPS
extern int scheme_check_long_mode(int long_mode);
# define CHECK_NESTED_GENERATE() if (scheme_check_long_mode(_jitl.long_jumps_default)) return 0;
#else
# define CHECK_NESTED_GENERATE() /* empty */
#endif
void *scheme_generate_one(mz_jit_state *old_jitter,
Generate_Proc generate,
void *data,

4
racket/src/racket/src/jitcall.c
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@ -1824,6 +1824,7 @@ int scheme_generate_app(Scheme_App_Rec *app, Scheme_Object **alt_rands, int num_
if (nc->code->start_code == scheme_on_demand_jit_code) {
if (nc->code->arity_code != sjc.in_progress_on_demand_jit_arity_code) {
scheme_on_demand_generate_lambda(nc, 0, NULL, 0);
CHECK_NESTED_GENERATE();
}
}
if (nc->code->start_code != scheme_on_demand_jit_code) {
@ -2166,6 +2167,7 @@ int scheme_generate_app(Scheme_App_Rec *app, Scheme_Object **alt_rands, int num_
sjc.shared_tail_code[dp][num_rands] = code;
}
code = sjc.shared_tail_code[dp][num_rands];
CHECK_NESTED_GENERATE();
if (direct_self) {
LOG_IT(("<-self\n"));
generate_self_tail_call(rator, jitter, num_rands, code, args_already_in_place, direct_flostack_offset,
@ -2231,6 +2233,7 @@ int scheme_generate_app(Scheme_App_Rec *app, Scheme_Object **alt_rands, int num_
sjc.shared_non_tail_code[4][num_rands][mo] = code;
}
unboxed_code = sjc.shared_non_tail_code[4][num_rands][mo];
CHECK_NESTED_GENERATE();
} else
unboxed_code = NULL;
#endif
@ -2243,6 +2246,7 @@ int scheme_generate_app(Scheme_App_Rec *app, Scheme_Object **alt_rands, int num_
}
LOG_IT(("<-non-tail %d %d %d\n", dp, num_rands, mo));
code = sjc.shared_non_tail_code[dp][num_rands][mo];
CHECK_NESTED_GENERATE();
if (nontail_self) {
generate_nontail_self_setup(jitter);

8
racket/src/racket/src/jitstate.c
View File

@ -162,6 +162,14 @@ static int check_long_mode(uintptr_t low, uintptr_t size)
return 0;
}
int scheme_check_long_mode(int jitter_long_jumps_default)
{
/* Relying on TSO: if another place provides a shared code pointer, then
seeing that pointer means that this place also sees any change
to `default-long_jumps` that applies to the pointer. */
return (jitter_long_jumps_default != default_long_jumps);
}
#endif