Move to a shared static RWX section

Does away with the need to mark a region as executable on load.
Also allows the self-modified stuff and hook trampolines to fit in the
same page, so we take up ever-so-slightly less memory.

Unfortunately I had issues getting the test binary to build correctly
and eventually decided to give up as it wasn't testing much of value
anyway.

Also note that the build now allows for .c and .S files with the same
basename, which required renaming the .o files, so you might want to
clean out your .build/ directory before building this one.

1 files changed, 5 insertions, 9 deletions

diff --git a/src/hook.c b/src/hook.c
index 0355c18..baaa710 100644
--- a/src/hook.c
+++ b/src/hook.c
@@ -28,14 +28,9 @@
 // Almost certainly breaks in some weird cases. Oh well! Most of the time,
 // vtable hooking is more reliable, this is only for, uh, emergencies.
 
-static _Alignas(4096) uchar trampolines[4096];
-static uchar *curtrampoline = trampolines;
-
-bool hook_init() {
-	// PE doesn't support rwx sections, not sure about ELF. Meh, just set it
-	// here instead.
-	return os_mprot(trampolines, 4096, PAGE_EXECUTE_READWRITE);
-}
+#define SPACE 2048 // NOTE: MUST match SPACE in hook.S!
+extern uchar _hook_trampolinespc[]; // defined in hook.S
+static uchar *curtrampoline = _hook_trampolinespc;
 
 struct hook_inline_prep_ret hook_inline_prep(void *func, void **trampoline) {
 	uchar *p = func;
@@ -61,7 +56,8 @@ struct hook_inline_prep_ret hook_inline_prep(void *func, void **trampoline) {
 		len += ilen;
 		if (len >= 5) {
 			// we should have statically made trampoline buffer size big enough
-			assume(curtrampoline - trampolines < sizeof(trampolines) - len - 6);
+			assume(curtrampoline - (uchar *)_hook_trampolinespc <
+					SPACE - len - 6);
 			*curtrampoline = len; // stuff length in there for quick unhooking
 			uchar *newtrampoline = curtrampoline + 1;
 			curtrampoline += len + 6;