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linux-user: Factor out guest space probing into a function

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Signed-off-by: Meador Inge <meadori@codesourcery.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Meador Inge 2012-07-26 16:50:01 +00:00 committed by Peter Maydell
parent cd8e407d24
commit dce104013d
2 changed files with 90 additions and 33 deletions
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110
linux-user/elfload.c
View File

@ -1426,6 +1426,73 @@ bool guest_validate_base(unsigned long guest_base)
}
#endif
unsigned long init_guest_space(unsigned long host_start,
unsigned long host_size,
unsigned long guest_start,
bool fixed)
{
unsigned long current_start, real_start;
int flags;
assert(host_start || host_size);
/* If just a starting address is given, then just verify that
* address. */
if (host_start && !host_size) {
if (guest_validate_base(host_start)) {
return host_start;
} else {
return (unsigned long)-1;
}
}
/* Setup the initial flags and start address. */
current_start = host_start & qemu_host_page_mask;
flags = MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE;
if (fixed) {
flags |= MAP_FIXED;
}
/* Otherwise, a non-zero size region of memory needs to be mapped
* and validated. */
while (1) {
/* Do not use mmap_find_vma here because that is limited to the
* guest address space. We are going to make the
* guest address space fit whatever we're given.
*/
real_start = (unsigned long)
mmap((void *)current_start, host_size, PROT_NONE, flags, -1, 0);
if (real_start == (unsigned long)-1) {
return (unsigned long)-1;
}
if ((real_start == current_start)
&& guest_validate_base(real_start - guest_start)) {
break;
}
/* That address didn't work. Unmap and try a different one.
* The address the host picked because is typically right at
* the top of the host address space and leaves the guest with
* no usable address space. Resort to a linear search. We
* already compensated for mmap_min_addr, so this should not
* happen often. Probably means we got unlucky and host
* address space randomization put a shared library somewhere
* inconvenient.
*/
munmap((void *)real_start, host_size);
current_start += qemu_host_page_size;
if (host_start == current_start) {
/* Theoretically possible if host doesn't have any suitably
* aligned areas. Normally the first mmap will fail.
*/
return (unsigned long)-1;
}
}
return real_start;
}
static void probe_guest_base(const char *image_name,
abi_ulong loaddr, abi_ulong hiaddr)
{
@ -1452,46 +1519,23 @@ static void probe_guest_base(const char *image_name,
}
}
host_size = hiaddr - loaddr;
while (1) {
/* Do not use mmap_find_vma here because that is limited to the
guest address space. We are going to make the
guest address space fit whatever we're given. */
real_start = (unsigned long)
mmap((void *)host_start, host_size, PROT_NONE,
MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE, -1, 0);
if (real_start == (unsigned long)-1) {
goto exit_perror;
}
guest_base = real_start - loaddr;
if ((real_start == host_start) &&
guest_validate_base(guest_base)) {
break;
}
/* That address didn't work. Unmap and try a different one.
The address the host picked because is typically right at
the top of the host address space and leaves the guest with
no usable address space. Resort to a linear search. We
already compensated for mmap_min_addr, so this should not
happen often. Probably means we got unlucky and host
address space randomization put a shared library somewhere
inconvenient. */
munmap((void *)real_start, host_size);
host_start += qemu_host_page_size;
if (host_start == loaddr) {
/* Theoretically possible if host doesn't have any suitably
aligned areas. Normally the first mmap will fail. */
errmsg = "Unable to find space for application";
goto exit_errmsg;
}
/* Setup the initial guest memory space with ranges gleaned from
* the ELF image that is being loaded.
*/
real_start = init_guest_space(host_start, host_size, loaddr, false);
if (real_start == (unsigned long)-1) {
errmsg = "Unable to find space for application";
goto exit_errmsg;
}
guest_base = real_start - loaddr;
qemu_log("Relocating guest address space from 0x"
TARGET_ABI_FMT_lx " to 0x%lx\n",
loaddr, real_start);
}
return;
exit_perror:
errmsg = strerror(errno);
exit_errmsg:
fprintf(stderr, "%s: %s\n", image_name, errmsg);
exit(-1);

13
linux-user/qemu.h
View File

@ -210,6 +210,19 @@ void fork_end(int child);
*/
bool guest_validate_base(unsigned long guest_base);
/* Creates the initial guest address space in the host memory space using
* the given host start address hint and size. The guest_start parameter
* specifies the start address of the guest space. guest_base will be the
* difference between the host start address computed by this function and
* guest_start. If fixed is specified, then the mapped address space must
* start at host_start. The real start address of the mapped memory space is
* returned or -1 if there was an error.
*/
unsigned long init_guest_space(unsigned long host_start,
unsigned long host_size,
unsigned long guest_start,
bool fixed);
#include "qemu-log.h"
/* strace.c */