From 15c4e8fe44e34eee4a13135eeb121b3b26e4cd1b Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Sat, 20 Mar 2021 10:57:19 -0600 Subject: [PATCH] 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 Tested-by: Roman Bolshakov Reviewed-by: Roman Bolshakov Message-Id: <20210320165720.1813545-2-richard.henderson@linaro.org> --- tcg/tcg.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/tcg/tcg.c b/tcg/tcg.c index de91bb6e9e..88c9e6f8a4 100644 --- a/tcg/tcg.c +++ b/tcg/tcg.c @@ -828,7 +828,6 @@ void tcg_region_init(void) size_t region_size; size_t n_regions; size_t i; - uintptr_t splitwx_diff; n_regions = tcg_n_regions(); @@ -858,8 +857,11 @@ void tcg_region_init(void) /* account for that last guard page */ 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++) { void *start, *end; int rc; @@ -867,10 +869,6 @@ void tcg_region_init(void) tcg_region_bounds(i, &start, &end); rc = qemu_mprotect_none(end, page_size); g_assert(!rc); - if (splitwx_diff) { - rc = qemu_mprotect_none(end + splitwx_diff, page_size); - g_assert(!rc); - } } tcg_region_trees_init(); -- 2.11.0