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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>
This commit is contained in:
Richard Henderson 2023-08-03 20:25:38 +00:00
parent e3d97d5c5d
commit 2d385be615
1 changed files with 27 additions and 36 deletions
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63
linux-user/elfload.c
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@ -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). */ * zero_bss:
static void zero_bss(abi_ulong elf_bss, abi_ulong last_bss, int prot) *
* 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; 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 if (start_bss < align_bss) {
qemu_host_page_size here and elsewhere in target_mmap, which int flags = page_get_flags(start_bss);
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); if (!(flags & PAGE_VALID)) {
host_end = (uintptr_t) g2h_untagged(last_bss); /* Map the start of the bss. */
host_map_start = REAL_HOST_PAGE_ALIGN(host_start); align_bss -= TARGET_PAGE_SIZE;
} else if (flags & PAGE_WRITE) {
if (host_map_start < host_end) { /* The page is already mapped writable. */
void *p = mmap((void *)host_map_start, host_end - host_map_start, memset(g2h_untagged(start_bss), 0, align_bss - start_bss);
prot, MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); } else {
if (p == MAP_FAILED) { /* Read-only zeros? */
perror("cannot mmap brk"); g_assert_not_reached();
exit(-1);
} }
} }
/* Ensure that the bss page(s) are valid */ return align_bss >= end_bss ||
if ((page_get_flags(last_bss-1) & prot) != prot) { target_mmap(align_bss, end_bss - align_bss, prot,
page_set_flags(elf_bss & TARGET_PAGE_MASK, last_bss - 1, MAP_FIXED | MAP_PRIVATE | MAP_ANON, -1, 0) != -1;
prot | PAGE_VALID);
}
if (host_start < host_map_start) {
memset((void *)host_start, 0, host_map_start - host_start);
}
} }
#if defined(TARGET_ARM) #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 the load segment requests extra zeros (e.g. bss), map it.
*/ */
if (eppnt->p_filesz < eppnt->p_memsz) { if (eppnt->p_filesz < eppnt->p_memsz &&
zero_bss(vaddr_ef, vaddr_em, elf_prot); !zero_bss(vaddr_ef, vaddr_em, elf_prot)) {
goto exit_mmap;
} }
} else if (eppnt->p_memsz != 0) { } else if (eppnt->p_memsz != 0) {
vaddr_len = eppnt->p_memsz + vaddr_po; vaddr_len = eppnt->p_memsz + vaddr_po;