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[PULL 27/34] tcg: Merge buffer protection and guard page protection
From: |
Richard Henderson |
Subject: |
[PULL 27/34] tcg: Merge buffer protection and guard page protection |
Date: |
Fri, 11 Jun 2021 16:41:37 -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.
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Luis Pires <luis.pires@eldorado.org.br>
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 e1790ce1e4..294cbd8e65 100644
--- a/tcg/region.c
+++ b/tcg/region.c
@@ -535,11 +535,6 @@ 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;
@@ -823,8 +818,7 @@ 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) {
@@ -884,18 +878,41 @@ 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
- [PULL 21/34] tcg: Move in_code_gen_buffer and tests to region.c, (continued)
- [PULL 21/34] tcg: Move in_code_gen_buffer and tests to region.c, Richard Henderson, 2021/06/11
- [PULL 23/34] tcg: Return the map protection from alloc_code_gen_buffer, Richard Henderson, 2021/06/11
- [PULL 13/34] accel/tcg: Use MiB in tcg_init_machine, Richard Henderson, 2021/06/11
- [PULL 26/34] tcg: Round the tb_size default from qemu_get_host_physmem, Richard Henderson, 2021/06/11
- [PULL 28/34] tcg: When allocating for !splitwx, begin with PROT_NONE, Richard Henderson, 2021/06/11
- [PULL 31/34] tcg: Fix documentation for tcg_constant_* vs tcg_temp_free_*, Richard Henderson, 2021/06/11
- [PULL 24/34] tcg: Sink qemu_madvise call to common code, Richard Henderson, 2021/06/11
- [PULL 22/34] tcg: Allocate code_gen_buffer into struct tcg_region_state, Richard Henderson, 2021/06/11
- [PULL 20/34] tcg: Tidy split_cross_256mb, Richard Henderson, 2021/06/11
- [PULL 25/34] util/osdep: Add qemu_mprotect_rw, Richard Henderson, 2021/06/11
- [PULL 27/34] tcg: Merge buffer protection and guard page protection,
Richard Henderson <=
- [PULL 29/34] tcg: Move tcg_init_ctx and tcg_ctx from accel/tcg/, Richard Henderson, 2021/06/11
- [PULL 32/34] tcg/arm: Fix tcg_out_op function signature, Richard Henderson, 2021/06/11
- [PULL 30/34] tcg: Introduce tcg_remove_ops_after, Richard Henderson, 2021/06/11
- [PULL 33/34] softfloat: Fix tp init in float32_exp2, Richard Henderson, 2021/06/11
- [PULL 34/34] docs/devel: Explain in more detail the TB chaining mechanisms, Richard Henderson, 2021/06/11
- Re: [PULL 00/34] tcg patch queue, Peter Maydell, 2021/06/13