Richard Henderson <richard.hender...@linaro.org> writes:
> Rely on target_mmap to handle guest vs host page size mismatch.
>
> Tested-by: Helge Deller <del...@gmx.de>
> Reviewed-by: Helge Deller <del...@gmx.de>
> Reviewed-by: Akihiko Odaki <akihiko.od...@daynix.com>
> Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
> ---
> linux-user/elfload.c | 54 +++++++++++++++++++-------------------------
> 1 file changed, 23 insertions(+), 31 deletions(-)
>
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index 964b21f997..6c28cb70ef 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -2213,44 +2213,36 @@ static abi_ulong setup_arg_pages(struct linux_binprm
> *bprm,
>
> /* Map and zero the bss. We need to explicitly zero any fractional pages
> after the data section (i.e. bss). */
> -static void zero_bss(abi_ulong elf_bss, abi_ulong last_bss, int prot)
> +static void zero_bss(abi_ulong start_bss, abi_ulong end_bss, int prot)
> {
> - uintptr_t host_start, host_map_start, host_end;
> + abi_ulong align_bss;
>
> - last_bss = TARGET_PAGE_ALIGN(last_bss);
> + align_bss = TARGET_PAGE_ALIGN(start_bss);
> + end_bss = TARGET_PAGE_ALIGN(end_bss);
>
> - /* ??? There is confusion between qemu_real_host_page_size and
> - qemu_host_page_size here and elsewhere in target_mmap, which
> - may lead to the end of the data section mapping from the file
> - not being mapped. At least there was an explicit test and
> - comment for that here, suggesting that "the file size must
> - be known". The comment probably pre-dates the introduction
> - of the fstat system call in target_mmap which does in fact
> - find out the size. What isn't clear is if the workaround
> - here is still actually needed. For now, continue with it,
> - but merge it with the "normal" mmap that would allocate the bss. */
> + if (start_bss < align_bss) {
> + int flags = page_get_flags(start_bss);
>
> - host_start = (uintptr_t) g2h_untagged(elf_bss);
> - host_end = (uintptr_t) g2h_untagged(last_bss);
> - host_map_start = REAL_HOST_PAGE_ALIGN(host_start);
> -
> - if (host_map_start < host_end) {
> - void *p = mmap((void *)host_map_start, host_end - host_map_start,
> - prot, MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> - if (p == MAP_FAILED) {
> - perror("cannot mmap brk");
> - exit(-1);
> + if (!(flags & PAGE_VALID)) {
> + /* Map the start of the bss. */
> + align_bss -= TARGET_PAGE_SIZE;
> + } else if (flags & PAGE_WRITE) {
> + /* The page is already mapped writable. */
> + memset(g2h_untagged(start_bss), 0, align_bss - start_bss);
> + } else {
> + /* Read-only zeros? */
> + g_assert_not_reached();
> }
> }
>
> - /* Ensure that the bss page(s) are valid */
> - if ((page_get_flags(last_bss-1) & prot) != prot) {
> - page_set_flags(elf_bss & TARGET_PAGE_MASK, last_bss - 1,
> - prot | PAGE_VALID);
> - }
> -
> - if (host_start < host_map_start) {
> - memset((void *)host_start, 0, host_map_start - host_start);
> + if (align_bss < end_bss) {
> + abi_long err = target_mmap(align_bss, end_bss - align_bss, prot,
> + MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
> + -1, 0);
> + if (err == -1) {
> + perror("cannot mmap brk");
> + exit(-1);
brk != bss even if brk generally comes after the bss section.
> + }
> }
> }
--
Alex Bennée
Virtualisation Tech Lead @ Linaro
