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[PATCH 25/26] tcg: Merge buffer protection and guard page protection
From: |
Richard Henderson |
Subject: |
[PATCH 25/26] tcg: Merge buffer protection and guard page protection |
Date: |
Wed, 10 Mar 2021 18:21:55 -0600 |
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 | 40 +++++++++++++++++++++++++++++-----------
1 file changed, 29 insertions(+), 11 deletions(-)
diff --git a/tcg/region.c b/tcg/region.c
index 93d03076d1..5b46172fb5 100644
--- a/tcg/region.c
+++ b/tcg/region.c
@@ -514,11 +514,6 @@ 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;
@@ -802,8 +797,7 @@ void tcg_region_init(size_t tb_size, int splitwx, unsigned
max_cpus)
{
size_t page_size;
size_t region_size;
- size_t i;
- int have_prot;
+ int have_prot, need_prot;
have_prot = alloc_code_gen_buffer(size_code_gen_buffer(tb_size),
splitwx, &error_fatal);
@@ -844,14 +838,38 @@ void tcg_region_init(size_t tb_size, int splitwx,
unsigned max_cpus)
/* init the region struct */
qemu_mutex_init(®ion.lock);
- /* Set guard pages. No need to do this for the rx_buf, only the rw_buf. */
- for (i = 0; i < region.n; i++) {
+ /*
+ * Set guard pages. No need to do this for the rx_buf, only the rw_buf.
+ * Work with the page protections set up with the initial mapping.
+ */
+ 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;
int rc;
tcg_region_bounds(i, &start, &end);
- rc = qemu_mprotect_none(end, page_size);
- g_assert(!rc);
+ if (have_prot != need_prot) {
+ 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) {
+ /* If guard-page permissions don't change, it isn't fatal. */
+ (void)qemu_mprotect_none(end, page_size);
+ }
}
tcg_region_trees_init();
--
2.25.1
- [PATCH 16/26] tcg: Move MAX_CODE_GEN_BUFFER_SIZE to tcg-target.h, (continued)
- [PATCH 16/26] tcg: Move MAX_CODE_GEN_BUFFER_SIZE to tcg-target.h, Richard Henderson, 2021/03/10
- [PATCH 13/26] accel/tcg: Merge tcg_exec_init into tcg_init_machine, Richard Henderson, 2021/03/10
- [PATCH 23/26] tcg: Do not set guard pages in the rx buffer, Richard Henderson, 2021/03/10
- [PATCH 21/26] tcg: Return the map protection from alloc_code_gen_buffer, Richard Henderson, 2021/03/10
- [PATCH 20/26] tcg: Allocate code_gen_buffer into struct tcg_region_state, Richard Henderson, 2021/03/10
- [PATCH 22/26] tcg: Sink qemu_madvise call to common code, Richard Henderson, 2021/03/10
- [PATCH 15/26] tcg: Introduce tcg_max_ctxs, Richard Henderson, 2021/03/10
- [PATCH 25/26] tcg: Merge buffer protection and guard page protection,
Richard Henderson <=
- [PATCH 24/26] util/osdep: Add qemu_mprotect_rw, Richard Henderson, 2021/03/10
- [PATCH 26/26] tcg: When allocating for !splitwx, begin with PROT_NONE, Richard Henderson, 2021/03/10
- Re: [PATCH 00/26] tcg: Workaround macOS 11.2 mprotect bug, no-reply, 2021/03/10