[IA64] update memory attribute aliasing documentation & test cases
Updates documentation and adds some test cases. Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com> Signed-off-by: Tony Luck <tony.luck@intel.com>
This commit is contained in:
Bjorn Helgaas
Tony Luck
parent
6d40fc514c
commit
ddd83eff58
2 changed files with 284 additions and 34 deletions
247
Documentation/ia64/aliasing-test.c
Normal file
247
Documentation/ia64/aliasing-test.c
Normal file
|
|
@ -0,0 +1,247 @@
|
|||
/*
|
||||
* Exercise /dev/mem mmap cases that have been troublesome in the past
|
||||
*
|
||||
* (c) Copyright 2007 Hewlett-Packard Development Company, L.P.
|
||||
* Bjorn Helgaas <bjorn.helgaas@hp.com>
|
||||
*
|
||||
* This program is free software; you can redistribute it and/or modify
|
||||
* it under the terms of the GNU General Public License version 2 as
|
||||
* published by the Free Software Foundation.
|
||||
*/
|
||||
|
||||
#include <stdlib.h>
|
||||
#include <stdio.h>
|
||||
#include <sys/types.h>
|
||||
#include <dirent.h>
|
||||
#include <fcntl.h>
|
||||
#include <fnmatch.h>
|
||||
#include <string.h>
|
||||
#include <sys/mman.h>
|
||||
#include <sys/stat.h>
|
||||
#include <unistd.h>
|
||||
|
||||
int sum;
|
||||
|
||||
int map_mem(char *path, off_t offset, size_t length, int touch)
|
||||
{
|
||||
int fd, rc;
|
||||
void *addr;
|
||||
int *c;
|
||||
|
||||
fd = open(path, O_RDWR);
|
||||
if (fd == -1) {
|
||||
perror(path);
|
||||
return -1;
|
||||
}
|
||||
|
||||
addr = mmap(NULL, length, PROT_READ|PROT_WRITE, MAP_SHARED, fd, offset);
|
||||
if (addr == MAP_FAILED)
|
||||
return 1;
|
||||
|
||||
if (touch) {
|
||||
c = (int *) addr;
|
||||
while (c < (int *) (offset + length))
|
||||
sum += *c++;
|
||||
}
|
||||
|
||||
rc = munmap(addr, length);
|
||||
if (rc == -1) {
|
||||
perror("munmap");
|
||||
return -1;
|
||||
}
|
||||
|
||||
close(fd);
|
||||
return 0;
|
||||
}
|
||||
|
||||
int scan_sysfs(char *path, char *file, off_t offset, size_t length, int touch)
|
||||
{
|
||||
struct dirent **namelist;
|
||||
char *name, *path2;
|
||||
int i, n, r, rc, result = 0;
|
||||
struct stat buf;
|
||||
|
||||
n = scandir(path, &namelist, 0, alphasort);
|
||||
if (n < 0) {
|
||||
perror("scandir");
|
||||
return -1;
|
||||
}
|
||||
|
||||
for (i = 0; i < n; i++) {
|
||||
name = namelist[i]->d_name;
|
||||
|
||||
if (fnmatch(".", name, 0) == 0)
|
||||
goto skip;
|
||||
if (fnmatch("..", name, 0) == 0)
|
||||
goto skip;
|
||||
|
||||
path2 = malloc(strlen(path) + strlen(name) + 3);
|
||||
strcpy(path2, path);
|
||||
strcat(path2, "/");
|
||||
strcat(path2, name);
|
||||
|
||||
if (fnmatch(file, name, 0) == 0) {
|
||||
rc = map_mem(path2, offset, length, touch);
|
||||
if (rc == 0)
|
||||
fprintf(stderr, "PASS: %s 0x%lx-0x%lx is %s\n", path2, offset, offset + length, touch ? "readable" : "mappable");
|
||||
else if (rc > 0)
|
||||
fprintf(stderr, "PASS: %s 0x%lx-0x%lx not mappable\n", path2, offset, offset + length);
|
||||
else {
|
||||
fprintf(stderr, "FAIL: %s 0x%lx-0x%lx not accessible\n", path2, offset, offset + length);
|
||||
return rc;
|
||||
}
|
||||
} else {
|
||||
r = lstat(path2, &buf);
|
||||
if (r == 0 && S_ISDIR(buf.st_mode)) {
|
||||
rc = scan_sysfs(path2, file, offset, length, touch);
|
||||
if (rc < 0)
|
||||
return rc;
|
||||
}
|
||||
}
|
||||
|
||||
result |= rc;
|
||||
free(path2);
|
||||
|
||||
skip:
|
||||
free(namelist[i]);
|
||||
}
|
||||
free(namelist);
|
||||
return rc;
|
||||
}
|
||||
|
||||
char buf[1024];
|
||||
|
||||
int read_rom(char *path)
|
||||
{
|
||||
int fd, rc;
|
||||
size_t size = 0;
|
||||
|
||||
fd = open(path, O_RDWR);
|
||||
if (fd == -1) {
|
||||
perror(path);
|
||||
return -1;
|
||||
}
|
||||
|
||||
rc = write(fd, "1", 2);
|
||||
if (rc <= 0) {
|
||||
perror("write");
|
||||
return -1;
|
||||
}
|
||||
|
||||
do {
|
||||
rc = read(fd, buf, sizeof(buf));
|
||||
if (rc > 0)
|
||||
size += rc;
|
||||
} while (rc > 0);
|
||||
|
||||
close(fd);
|
||||
return size;
|
||||
}
|
||||
|
||||
int scan_rom(char *path, char *file)
|
||||
{
|
||||
struct dirent **namelist;
|
||||
char *name, *path2;
|
||||
int i, n, r, rc, result = 0;
|
||||
struct stat buf;
|
||||
|
||||
n = scandir(path, &namelist, 0, alphasort);
|
||||
if (n < 0) {
|
||||
perror("scandir");
|
||||
return -1;
|
||||
}
|
||||
|
||||
for (i = 0; i < n; i++) {
|
||||
name = namelist[i]->d_name;
|
||||
|
||||
if (fnmatch(".", name, 0) == 0)
|
||||
goto skip;
|
||||
if (fnmatch("..", name, 0) == 0)
|
||||
goto skip;
|
||||
|
||||
path2 = malloc(strlen(path) + strlen(name) + 3);
|
||||
strcpy(path2, path);
|
||||
strcat(path2, "/");
|
||||
strcat(path2, name);
|
||||
|
||||
if (fnmatch(file, name, 0) == 0) {
|
||||
rc = read_rom(path2);
|
||||
|
||||
/*
|
||||
* It's OK if the ROM is unreadable. Maybe there
|
||||
* is no ROM, or some other error ocurred. The
|
||||
* important thing is that no MCA happened.
|
||||
*/
|
||||
if (rc > 0)
|
||||
fprintf(stderr, "PASS: %s read %ld bytes\n", path2, rc);
|
||||
else {
|
||||
fprintf(stderr, "PASS: %s not readable\n", path2);
|
||||
return rc;
|
||||
}
|
||||
} else {
|
||||
r = lstat(path2, &buf);
|
||||
if (r == 0 && S_ISDIR(buf.st_mode)) {
|
||||
rc = scan_rom(path2, file);
|
||||
if (rc < 0)
|
||||
return rc;
|
||||
}
|
||||
}
|
||||
|
||||
result |= rc;
|
||||
free(path2);
|
||||
|
||||
skip:
|
||||
free(namelist[i]);
|
||||
}
|
||||
free(namelist);
|
||||
return rc;
|
||||
}
|
||||
|
||||
main()
|
||||
{
|
||||
int rc;
|
||||
|
||||
if (map_mem("/dev/mem", 0, 0xA0000, 1) == 0)
|
||||
fprintf(stderr, "PASS: /dev/mem 0x0-0xa0000 is readable\n");
|
||||
else
|
||||
fprintf(stderr, "FAIL: /dev/mem 0x0-0xa0000 not accessible\n");
|
||||
|
||||
/*
|
||||
* It's not safe to blindly read the VGA frame buffer. If you know
|
||||
* how to poke the card the right way, it should respond, but it's
|
||||
* not safe in general. Many machines, e.g., Intel chipsets, cover
|
||||
* up a non-responding card by just returning -1, but others will
|
||||
* report the failure as a machine check.
|
||||
*/
|
||||
if (map_mem("/dev/mem", 0xA0000, 0x20000, 0) == 0)
|
||||
fprintf(stderr, "PASS: /dev/mem 0xa0000-0xc0000 is mappable\n");
|
||||
else
|
||||
fprintf(stderr, "FAIL: /dev/mem 0xa0000-0xc0000 not accessible\n");
|
||||
|
||||
if (map_mem("/dev/mem", 0xC0000, 0x40000, 1) == 0)
|
||||
fprintf(stderr, "PASS: /dev/mem 0xc0000-0x100000 is readable\n");
|
||||
else
|
||||
fprintf(stderr, "FAIL: /dev/mem 0xc0000-0x100000 not accessible\n");
|
||||
|
||||
/*
|
||||
* Often you can map all the individual pieces above (0-0xA0000,
|
||||
* 0xA0000-0xC0000, and 0xC0000-0x100000), but can't map the whole
|
||||
* thing at once. This is because the individual pieces use different
|
||||
* attributes, and there's no single attribute supported over the
|
||||
* whole region.
|
||||
*/
|
||||
rc = map_mem("/dev/mem", 0, 1024*1024, 0);
|
||||
if (rc == 0)
|
||||
fprintf(stderr, "PASS: /dev/mem 0x0-0x100000 is mappable\n");
|
||||
else if (rc > 0)
|
||||
fprintf(stderr, "PASS: /dev/mem 0x0-0x100000 not mappable\n");
|
||||
else
|
||||
fprintf(stderr, "FAIL: /dev/mem 0x0-0x100000 not accessible\n");
|
||||
|
||||
scan_sysfs("/sys/class/pci_bus", "legacy_mem", 0, 0xA0000, 1);
|
||||
scan_sysfs("/sys/class/pci_bus", "legacy_mem", 0xA0000, 0x20000, 0);
|
||||
scan_sysfs("/sys/class/pci_bus", "legacy_mem", 0xC0000, 0x40000, 1);
|
||||
scan_sysfs("/sys/class/pci_bus", "legacy_mem", 0, 1024*1024, 0);
|
||||
|
||||
scan_rom("/sys/devices", "rom");
|
||||
}
|
||||
|
|
@ -112,16 +112,6 @@ POTENTIAL ATTRIBUTE ALIASING CASES
|
|||
|
||||
The /dev/mem mmap constraints apply.
|
||||
|
||||
However, since this is for mapping legacy MMIO space, WB access
|
||||
does not make sense. This matters on machines without legacy
|
||||
VGA support: these machines may have WB memory for the entire
|
||||
first megabyte (or even the entire first granule).
|
||||
|
||||
On these machines, we could mmap legacy_mem as WB, which would
|
||||
be safe in terms of attribute aliasing, but X has no way of
|
||||
knowing that it is accessing regular memory, not a frame buffer,
|
||||
so the kernel should fail the mmap rather than doing it with WB.
|
||||
|
||||
read/write of /dev/mem
|
||||
|
||||
This uses copy_from_user(), which implicitly uses a kernel
|
||||
|
|
@ -138,14 +128,20 @@ POTENTIAL ATTRIBUTE ALIASING CASES
|
|||
|
||||
ioremap()
|
||||
|
||||
This returns a kernel identity mapping for use inside the
|
||||
kernel.
|
||||
This returns a mapping for use inside the kernel.
|
||||
|
||||
If the region is in kern_memmap, we should use the attribute
|
||||
specified there. Otherwise, if the EFI memory map reports that
|
||||
the entire granule supports WB, we should use that (granules
|
||||
that are partially reserved or occupied by firmware do not appear
|
||||
in kern_memmap). Otherwise, we should use a UC mapping.
|
||||
specified there.
|
||||
|
||||
If the EFI memory map reports that the entire granule supports
|
||||
WB, we should use that (granules that are partially reserved
|
||||
or occupied by firmware do not appear in kern_memmap).
|
||||
|
||||
If the granule contains non-WB memory, but we can cover the
|
||||
region safely with kernel page table mappings, we can use
|
||||
ioremap_page_range() as most other architectures do.
|
||||
|
||||
Failing all of the above, we have to fall back to a UC mapping.
|
||||
|
||||
PAST PROBLEM CASES
|
||||
|
||||
|
|
@ -158,7 +154,7 @@ PAST PROBLEM CASES
|
|||
succeed. It may create either WB or UC user mappings, depending
|
||||
on whether the region is in kern_memmap or the EFI memory map.
|
||||
|
||||
mmap of 0x0-0xA0000 /dev/mem by "hwinfo" on HP sx1000 with VGA enabled
|
||||
mmap of 0x0-0x9FFFF /dev/mem by "hwinfo" on HP sx1000 with VGA enabled
|
||||
|
||||
See https://bugzilla.novell.com/show_bug.cgi?id=140858.
|
||||
|
||||
|
|
@ -171,28 +167,25 @@ PAST PROBLEM CASES
|
|||
so it is safe to use WB mappings.
|
||||
|
||||
The kernel VGA driver may ioremap the VGA frame buffer at 0xA0000,
|
||||
which will use a granule-sized UC mapping covering 0-0xFFFFF. This
|
||||
granule covers some WB-only memory, but since UC is non-speculative,
|
||||
the processor will never generate an uncacheable reference to the
|
||||
WB-only areas unless the driver explicitly touches them.
|
||||
which uses a granule-sized UC mapping. This granule will cover some
|
||||
WB-only memory, but since UC is non-speculative, the processor will
|
||||
never generate an uncacheable reference to the WB-only areas unless
|
||||
the driver explicitly touches them.
|
||||
|
||||
mmap of 0x0-0xFFFFF legacy_mem by "X"
|
||||
|
||||
If the EFI memory map reports this entire range as WB, there
|
||||
is no VGA MMIO hole, and the mmap should fail or be done with
|
||||
a WB mapping.
|
||||
If the EFI memory map reports that the entire range supports the
|
||||
same attributes, we can allow the mmap (and we will prefer WB if
|
||||
supported, as is the case with HP sx[12]000 machines with VGA
|
||||
disabled).
|
||||
|
||||
There's no easy way for X to determine whether the 0xA0000-0xBFFFF
|
||||
region is a frame buffer or just memory, so I think it's best to
|
||||
just fail this mmap request rather than using a WB mapping. As
|
||||
far as I know, there's no need to map legacy_mem with WB
|
||||
mappings.
|
||||
If EFI reports the range as partly WB and partly UC (as on sx[12]000
|
||||
machines with VGA enabled), we must fail the mmap because there's no
|
||||
safe attribute to use.
|
||||
|
||||
Otherwise, a UC mapping of the entire region is probably safe.
|
||||
The VGA hole means the region will not be in kern_memmap. The
|
||||
HP sx1000 chipset doesn't support UC access to the memory surrounding
|
||||
the VGA hole, but X doesn't need that area anyway and should not
|
||||
reference it.
|
||||
If EFI reports some of the range but not all (as on Intel firmware
|
||||
that doesn't report the VGA frame buffer at all), we should fail the
|
||||
mmap and force the user to map just the specific region of interest.
|
||||
|
||||
mmap of 0xA0000-0xBFFFF legacy_mem by "X" on HP sx1000 with VGA disabled
|
||||
|
||||
|
|
@ -202,6 +195,16 @@ PAST PROBLEM CASES
|
|||
This is a special case of the previous case, and the mmap should
|
||||
fail for the same reason as above.
|
||||
|
||||
read of /sys/devices/.../rom
|
||||
|
||||
For VGA devices, this may cause an ioremap() of 0xC0000. This
|
||||
used to be done with a UC mapping, because the VGA frame buffer
|
||||
at 0xA0000 prevents use of a WB granule. The UC mapping causes
|
||||
an MCA on HP sx[12]000 chipsets.
|
||||
|
||||
We should use WB page table mappings to avoid covering the VGA
|
||||
frame buffer.
|
||||
|
||||
NOTES
|
||||
|
||||
[1] SDM rev 2.2, vol 2, sec 4.4.1.
|
||||
|
|
|
|||
Loading…
Reference in a new issue