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author | Richard Henderson <richard.henderson@linaro.org> | 2023-08-03 20:25:38 +0000 |
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committer | Richard Henderson <richard.henderson@linaro.org> | 2023-08-08 13:27:17 -0700 |
commit | 2d385be6152222b61540639d2c41cdc48efec22c (patch) | |
tree | f873b79fbd677fd51a727c0d1a72625e7e23fd7b /linux-user | |
parent | e3d97d5c5d4b357ff8e2e891c557e6cef752145a (diff) | |
download | qemu-2d385be6152222b61540639d2c41cdc48efec22c.zip qemu-2d385be6152222b61540639d2c41cdc48efec22c.tar.gz qemu-2d385be6152222b61540639d2c41cdc48efec22c.tar.bz2 |
linux-user: Do not adjust zero_bss for host page size
Rely on target_mmap to handle guest vs host page size mismatch.
Tested-by: Helge Deller <deller@gmx.de>
Reviewed-by: Helge Deller <deller@gmx.de>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Diffstat (limited to 'linux-user')
-rw-r--r-- | linux-user/elfload.c | 69 |
1 files changed, 30 insertions, 39 deletions
diff --git a/linux-user/elfload.c b/linux-user/elfload.c index 964b21f..881fdeb 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -2211,47 +2211,37 @@ 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) +/** + * zero_bss: + * + * Map and zero the bss. We need to explicitly zero any fractional pages + * after the data section (i.e. bss). Return false on mapping failure. + */ +static bool zero_bss(abi_ulong start_bss, abi_ulong end_bss, int prot) { - uintptr_t host_start, host_map_start, host_end; - - last_bss = TARGET_PAGE_ALIGN(last_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. */ - - 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); - } - } + abi_ulong align_bss; - /* 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); - } + align_bss = TARGET_PAGE_ALIGN(start_bss); + end_bss = TARGET_PAGE_ALIGN(end_bss); - if (host_start < host_map_start) { - memset((void *)host_start, 0, host_map_start - host_start); + if (start_bss < align_bss) { + int flags = page_get_flags(start_bss); + + 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(); + } } + + return align_bss >= end_bss || + target_mmap(align_bss, end_bss - align_bss, prot, + MAP_FIXED | MAP_PRIVATE | MAP_ANON, -1, 0) != -1; } #if defined(TARGET_ARM) @@ -3255,8 +3245,9 @@ static void load_elf_image(const char *image_name, int image_fd, /* * If the load segment requests extra zeros (e.g. bss), map it. */ - if (eppnt->p_filesz < eppnt->p_memsz) { - zero_bss(vaddr_ef, vaddr_em, elf_prot); + if (eppnt->p_filesz < eppnt->p_memsz && + !zero_bss(vaddr_ef, vaddr_em, elf_prot)) { + goto exit_mmap; } } else if (eppnt->p_memsz != 0) { vaddr_len = eppnt->p_memsz + vaddr_po; |