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tcg: Do not set guard pages on the rx portion of code_gen_buffer 

The rw portion of the buffer is the only one in which overruns
can be generated.  Allow the rx portion to be more completely
covered by huge pages.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Roman Bolshakov <r.bolshakov@yadro.com>
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Message-Id: <20210320165720.1813545-2-richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2021-03-20 10:57:19 -06:00
parent 2664699471
commit 15c4e8fe44
1 changed files with 5 additions and 7 deletions
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12
tcg/tcg.c
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@ -828,7 +828,6 @@ void tcg_region_init(void)
size_t region_size; size_t region_size;
size_t n_regions; size_t n_regions;
size_t i; size_t i;
uintptr_t splitwx_diff;
n_regions = tcg_n_regions(); n_regions = tcg_n_regions();
@ -858,8 +857,11 @@ void tcg_region_init(void)
/* account for that last guard page */ /* account for that last guard page */
region.end -= page_size; region.end -= page_size;
/* set guard pages */ /*
splitwx_diff = tcg_splitwx_diff; * 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.
*/
for (i = 0; i < region.n; i++) { for (i = 0; i < region.n; i++) {
void *start, *end; void *start, *end;
int rc; int rc;
@ -867,10 +869,6 @@ void tcg_region_init(void)
tcg_region_bounds(i, &start, &end); tcg_region_bounds(i, &start, &end);
rc = qemu_mprotect_none(end, page_size); rc = qemu_mprotect_none(end, page_size);
g_assert(!rc); g_assert(!rc);
if (splitwx_diff) {
rc = qemu_mprotect_none(end + splitwx_diff, page_size);
g_assert(!rc);
}
} }
tcg_region_trees_init(); tcg_region_trees_init();