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[PATCH v3 26/28] tcg: Merge buffer protection and guard page protection
From: |
Richard Henderson |
Subject: |
[PATCH v3 26/28] tcg: Merge buffer protection and guard page protection |
Date: |
Sun, 2 May 2021 16:18:42 -0700 |
Do not handle protections on a case-by-case basis in the
various alloc_code_gen_buffer instances; do it within a
single loop in tcg_region_init.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
tcg/region.c | 45 +++++++++++++++++++++++++++++++--------------
1 file changed, 31 insertions(+), 14 deletions(-)
diff --git a/tcg/region.c b/tcg/region.c
index 49764b40dc..604530b902 100644
--- a/tcg/region.c
+++ b/tcg/region.c
@@ -530,11 +530,6 @@ static int alloc_code_gen_buffer(size_t tb_size, int
splitwx, Error **errp)
}
#endif
- if (qemu_mprotect_rwx(buf, size)) {
- error_setg_errno(errp, errno, "mprotect of jit buffer");
- return false;
- }
-
region.start_aligned = buf;
region.total_size = size;
@@ -818,8 +813,7 @@ void tcg_region_init(size_t tb_size, int splitwx, unsigned
max_cpus)
{
const size_t page_size = qemu_real_host_page_size;
size_t region_size;
- size_t i;
- int have_prot;
+ int have_prot, need_prot;
/* Size the buffer. */
if (tb_size == 0) {
@@ -879,18 +873,41 @@ void tcg_region_init(size_t tb_size, int splitwx,
unsigned max_cpus)
* Set guard pages in the rw buffer, as that's the one into which
* buffer overruns could occur. Do not set guard pages in the rx
* buffer -- let that one use hugepages throughout.
+ * Work with the page protections set up with the initial mapping.
*/
- for (i = 0; i < region.n; i++) {
+ need_prot = PAGE_READ | PAGE_WRITE;
+#ifndef CONFIG_TCG_INTERPRETER
+ if (tcg_splitwx_diff == 0) {
+ need_prot |= PAGE_EXEC;
+ }
+#endif
+ for (size_t i = 0, n = region.n; i < n; i++) {
void *start, *end;
tcg_region_bounds(i, &start, &end);
+ if (have_prot != need_prot) {
+ int rc;
- /*
- * macOS 11.2 has a bug (Apple Feedback FB8994773) in which mprotect
- * rejects a permission change from RWX -> NONE. Guard pages are
- * nice for bug detection but are not essential; ignore any failure.
- */
- (void)qemu_mprotect_none(end, page_size);
+ if (need_prot == (PAGE_READ | PAGE_WRITE | PAGE_EXEC)) {
+ rc = qemu_mprotect_rwx(start, end - start);
+ } else if (need_prot == (PAGE_READ | PAGE_WRITE)) {
+ rc = qemu_mprotect_rw(start, end - start);
+ } else {
+ g_assert_not_reached();
+ }
+ if (rc) {
+ error_setg_errno(&error_fatal, errno,
+ "mprotect of jit buffer");
+ }
+ }
+ if (have_prot != 0) {
+ /*
+ * macOS 11.2 has a bug (Apple Feedback FB8994773) in which
mprotect
+ * rejects a permission change from RWX -> NONE. Guard pages are
+ * nice for bug detection but are not essential; ignore any
failure.
+ */
+ (void)qemu_mprotect_none(end, page_size);
+ }
}
tcg_region_trees_init();
--
2.25.1
- [PATCH v3 16/28] tcg: Replace region.end with region.total_size, (continued)
- [PATCH v3 16/28] tcg: Replace region.end with region.total_size, Richard Henderson, 2021/05/02
- [PATCH v3 24/28] util/osdep: Add qemu_mprotect_rw, Richard Henderson, 2021/05/02
- [PATCH v3 17/28] tcg: Rename region.start to region.after_prologue, Richard Henderson, 2021/05/02
- [PATCH v3 22/28] tcg: Return the map protection from alloc_code_gen_buffer, Richard Henderson, 2021/05/02
- [PATCH v3 21/28] tcg: Allocate code_gen_buffer into struct tcg_region_state, Richard Henderson, 2021/05/02
- [PATCH v3 20/28] tcg: Move in_code_gen_buffer and tests to region.c, Richard Henderson, 2021/05/02
- [PATCH v3 23/28] tcg: Sink qemu_madvise call to common code, Richard Henderson, 2021/05/02
- [PATCH v3 27/28] tcg: When allocating for !splitwx, begin with PROT_NONE, Richard Henderson, 2021/05/02
- [PATCH v3 28/28] tcg: Move tcg_init_ctx and tcg_ctx from accel/tcg/, Richard Henderson, 2021/05/02
- [PATCH v3 19/28] tcg: Tidy split_cross_256mb, Richard Henderson, 2021/05/02
- [PATCH v3 26/28] tcg: Merge buffer protection and guard page protection,
Richard Henderson <=
- [PATCH v3 09/28] accel/tcg: Move alloc_code_gen_buffer to tcg/region.c, Richard Henderson, 2021/05/02
- [PATCH v3 12/28] accel/tcg: Merge tcg_exec_init into tcg_init_machine, Richard Henderson, 2021/05/02
- [PATCH v3 13/28] accel/tcg: Pass down max_cpus to tcg_init, Richard Henderson, 2021/05/02
- [PATCH v3 14/28] tcg: Introduce tcg_max_ctxs, Richard Henderson, 2021/05/02
- [PATCH v3 25/28] tcg: Round the tb_size default from qemu_get_host_physmem, Richard Henderson, 2021/05/02
- Re: [PATCH v3 00/28] tcg: Clean up code_gen_buffer allocation, no-reply, 2021/05/02