On 1/2/24 05:57, Richard Henderson wrote:
Use qemu_real_host_page_size. If the commpage is not within reserved_va, use MAP_FIXED_NOREPLACE.Signed-off-by: Richard Henderson <richard.hender...@linaro.org> --- linux-user/elfload.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/linux-user/elfload.c b/linux-user/elfload.c index 4fcc490ce6..2e2b1b0784 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -459,6 +459,7 @@ enum { static bool init_guest_commpage(void) { ARMCPU *cpu = ARM_CPU(thread_cpu); + int host_page_size = qemu_real_host_page_size(); abi_ptr commpage; void *want; void *addr; @@ -471,10 +472,12 @@ static bool init_guest_commpage(void) return true; }- commpage = HI_COMMPAGE & -qemu_host_page_size;+ commpage = HI_COMMPAGE & -host_page_size; want = g2h_untagged(commpage); - addr = mmap(want, qemu_host_page_size, PROT_READ | PROT_WRITE, - MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0); + addr = mmap(want, host_page_size, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE | + (commpage < reserved_va ? MAP_FIXED : MAP_FIXED_NOREPLACE), + -1, 0);if (addr == MAP_FAILED) {perror("Allocating guest commpage"); @@ -487,12 +490,12 @@ static bool init_guest_commpage(void) /* Set kernel helper versions; rest of page is 0. */ __put_user(5, (uint32_t *)g2h_untagged(0xffff0ffcu));- if (mprotect(addr, qemu_host_page_size, PROT_READ)) {+ if (mprotect(addr, host_page_size, PROT_READ)) { perror("Protecting guest commpage"); exit(EXIT_FAILURE); }- page_set_flags(commpage, commpage | ~qemu_host_page_mask,+ page_set_flags(commpage, commpage | (host_page_size - 1), PAGE_READ | PAGE_EXEC | PAGE_VALID); return true; }
To confirm if I understand correctly, when using a reserved va, the contiguous address space is reserved using mmap, thus MAP_FIXED_NOREPLACE would fail when hitting it?
Reviewed-by: Pierrick Bouvier <pierrick.bouv...@linaro.org>
