>From 40fb16a360d9c6459afee91dc793c1e3374feb94
From: Tom Spink <[email protected]>
This patch makes os_get_task_size locate the bottom of the address space,
as well as the top. This is for systems which put a lower limit on mmap
addresses. It works by manually scanning pages from zero onwards until a
valid page is found.
Because the bottom of the address space may not be zero, it's not
sufficient to assume the top of the address space is the size of the
address space. The size is the difference between the top address and
bottom address.
[[email protected]: changed the name to reflect that this function is
supposed to return the top of the process address space, not its size and
changed the return value to reflect that. Also some minor formatting
changes]
Signed-off-by: Tom Spink <[email protected]>
Signed-off-by: Jeff Dike <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
---
arch/um/include/os.h | 2 +-
arch/um/kernel/um_arch.c | 2 +-
arch/um/os-Linux/sys-i386/task_size.c | 38 +++++++++++++++++++++++-------
arch/um/os-Linux/sys-x86_64/task_size.c | 2 +-
4 files changed, 32 insertions(+), 12 deletions(-)
diff --git a/arch/um/include/os.h b/arch/um/include/os.h
index 32c799e..2d0a2a6 100644
--- a/arch/um/include/os.h
+++ b/arch/um/include/os.h
@@ -298,6 +298,6 @@ extern int os_arch_prctl(int pid, int code, unsigned long *addr);
extern int get_pty(void);
/* sys-$ARCH/task_size.c */
-extern unsigned long os_get_task_size(void);
+extern unsigned long os_get_top_address(void);
#endif
diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
index 9cecb42..d1fe222 100644
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -273,7 +273,7 @@ int __init linux_main(int argc, char **argv)
if (have_root == 0)
add_arg(DEFAULT_COMMAND_LINE);
- host_task_size = os_get_task_size();
+ host_task_size = os_get_top_address();
/*
* TASK_SIZE needs to be PGDIR_SIZE aligned or else exit_mmap craps
* out
diff --git a/arch/um/os-Linux/sys-i386/task_size.c b/arch/um/os-Linux/sys-i386/task_size.c
index 48d211b..4d26d5d 100644
--- a/arch/um/os-Linux/sys-i386/task_size.c
+++ b/arch/um/os-Linux/sys-i386/task_size.c
@@ -63,7 +63,7 @@ static int page_ok(unsigned long page)
return ok;
}
-unsigned long os_get_task_size(void)
+unsigned long os_get_top_address(void)
{
struct sigaction sa, old;
unsigned long bottom = 0;
@@ -76,9 +76,9 @@ unsigned long os_get_task_size(void)
* hosts, but shouldn't hurt otherwise.
*/
unsigned long top = 0xffffd000 >> UM_KERN_PAGE_SHIFT;
- unsigned long test;
+ unsigned long test, original;
- printf("Locating the top of the address space ... ");
+ printf("Locating the bottom of the address space ... ");
fflush(stdout);
/*
@@ -88,14 +88,32 @@ unsigned long os_get_task_size(void)
sa.sa_handler = segfault;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_NODEFER;
- sigaction(SIGSEGV, &sa, &old);
+ if (sigaction(SIGSEGV, &sa, &old)) {
+ perror("os_get_top_address");
+ exit(1);
+ }
- if (!page_ok(bottom)) {
- fprintf(stderr, "Address 0x%x no good?\n",
- bottom << UM_KERN_PAGE_SHIFT);
+ /* Manually scan the address space, bottom-up, until we find
+ * the first valid page (or run out of them).
+ */
+ for (bottom = 0; bottom < top; bottom++) {
+ if (page_ok(bottom))
+ break;
+ }
+
+ /* If we've got this far, we ran out of pages. */
+ if (bottom == top) {
+ fprintf(stderr, "Unable to determine bottom of address "
+ "space.\n");
exit(1);
}
+ printf("0x%x\n", bottom << UM_KERN_PAGE_SHIFT);
+ printf("Locating the top of the address space ... ");
+ fflush(stdout);
+
+ original = bottom;
+
/* This could happen with a 4G/4G split */
if (page_ok(top))
goto out;
@@ -110,8 +128,10 @@ unsigned long os_get_task_size(void)
out:
/* Restore the old SIGSEGV handling */
- sigaction(SIGSEGV, &old, NULL);
-
+ if (sigaction(SIGSEGV, &old, NULL)) {
+ perror("os_get_top_address");
+ exit(1);
+ }
top <<= UM_KERN_PAGE_SHIFT;
printf("0x%x\n", top);
fflush(stdout);
diff --git a/arch/um/os-Linux/sys-x86_64/task_size.c b/arch/um/os-Linux/sys-x86_64/task_size.c
index fad6f57..26a0dd1 100644
--- a/arch/um/os-Linux/sys-x86_64/task_size.c
+++ b/arch/um/os-Linux/sys-x86_64/task_size.c
@@ -1,4 +1,4 @@
-unsigned long os_get_task_size(unsigned long shift)
+unsigned long os_get_top_address(unsigned long shift)
{
/* The old value of CONFIG_TOP_ADDR */
return 0x7fc0000000;
--
1.5.5.1
This is a note to let you know that we have just queued up the patch titled
Subject: uml: deal with inaccessible address space start
to the 2.6.25-stable tree. Its filename is
uml-deal-with-inaccessible-address-space-start.patch
A git repo of this tree can be found at
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
>From [email protected] Tue Aug 5 13:14:42 2008
From: Tom Spink <[email protected]>
Date: Tue, 5 Aug 2008 16:14:06 -0400
Subject: uml: deal with inaccessible address space start
To: [email protected]
Cc: LKML <[email protected]>, uml-devel <[email protected]>
Message-ID: <[email protected]>
Content-Disposition: inline
From: Tom Spink <[email protected]>
commit 40fb16a360d9c6459afee91dc793c1e3374feb94 upstream
This patch makes os_get_task_size locate the bottom of the address space,
as well as the top. This is for systems which put a lower limit on mmap
addresses. It works by manually scanning pages from zero onwards until a
valid page is found.
Because the bottom of the address space may not be zero, it's not
sufficient to assume the top of the address space is the size of the
address space. The size is the difference between the top address and
bottom address.
[[email protected]: changed the name to reflect that this function is
supposed to return the top of the process address space, not its size and
changed the return value to reflect that. Also some minor formatting
changes]
Signed-off-by: Tom Spink <[email protected]>
Signed-off-by: Jeff Dike <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/um/include/os.h | 2 -
arch/um/kernel/um_arch.c | 2 -
arch/um/os-Linux/sys-i386/task_size.c | 38 ++++++++++++++++++++++++--------
arch/um/os-Linux/sys-x86_64/task_size.c | 2 -
4 files changed, 32 insertions(+), 12 deletions(-)
--- a/arch/um/include/os.h
+++ b/arch/um/include/os.h
@@ -298,6 +298,6 @@ extern int os_arch_prctl(int pid, int co
extern int get_pty(void);
/* sys-$ARCH/task_size.c */
-extern unsigned long os_get_task_size(void);
+extern unsigned long os_get_top_address(void);
#endif
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -273,7 +273,7 @@ int __init linux_main(int argc, char **a
if (have_root == 0)
add_arg(DEFAULT_COMMAND_LINE);
- host_task_size = os_get_task_size();
+ host_task_size = os_get_top_address();
/*
* TASK_SIZE needs to be PGDIR_SIZE aligned or else exit_mmap craps
* out
--- a/arch/um/os-Linux/sys-i386/task_size.c
+++ b/arch/um/os-Linux/sys-i386/task_size.c
@@ -63,7 +63,7 @@ static int page_ok(unsigned long page)
return ok;
}
-unsigned long os_get_task_size(void)
+unsigned long os_get_top_address(void)
{
struct sigaction sa, old;
unsigned long bottom = 0;
@@ -76,9 +76,9 @@ unsigned long os_get_task_size(void)
* hosts, but shouldn't hurt otherwise.
*/
unsigned long top = 0xffffd000 >> UM_KERN_PAGE_SHIFT;
- unsigned long test;
+ unsigned long test, original;
- printf("Locating the top of the address space ... ");
+ printf("Locating the bottom of the address space ... ");
fflush(stdout);
/*
@@ -88,14 +88,32 @@ unsigned long os_get_task_size(void)
sa.sa_handler = segfault;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_NODEFER;
- sigaction(SIGSEGV, &sa, &old);
+ if (sigaction(SIGSEGV, &sa, &old)) {
+ perror("os_get_top_address");
+ exit(1);
+ }
- if (!page_ok(bottom)) {
- fprintf(stderr, "Address 0x%x no good?\n",
- bottom << UM_KERN_PAGE_SHIFT);
+ /* Manually scan the address space, bottom-up, until we find
+ * the first valid page (or run out of them).
+ */
+ for (bottom = 0; bottom < top; bottom++) {
+ if (page_ok(bottom))
+ break;
+ }
+
+ /* If we've got this far, we ran out of pages. */
+ if (bottom == top) {
+ fprintf(stderr, "Unable to determine bottom of address "
+ "space.\n");
exit(1);
}
+ printf("0x%x\n", bottom << UM_KERN_PAGE_SHIFT);
+ printf("Locating the top of the address space ... ");
+ fflush(stdout);
+
+ original = bottom;
+
/* This could happen with a 4G/4G split */
if (page_ok(top))
goto out;
@@ -110,8 +128,10 @@ unsigned long os_get_task_size(void)
out:
/* Restore the old SIGSEGV handling */
- sigaction(SIGSEGV, &old, NULL);
-
+ if (sigaction(SIGSEGV, &old, NULL)) {
+ perror("os_get_top_address");
+ exit(1);
+ }
top <<= UM_KERN_PAGE_SHIFT;
printf("0x%x\n", top);
fflush(stdout);
--- a/arch/um/os-Linux/sys-x86_64/task_size.c
+++ b/arch/um/os-Linux/sys-x86_64/task_size.c
@@ -1,4 +1,4 @@
-unsigned long os_get_task_size(unsigned long shift)
+unsigned long os_get_top_address(unsigned long shift)
{
/* The old value of CONFIG_TOP_ADDR */
return 0x7fc0000000;
Patches currently in stable-queue which might be from [email protected] are
queue-2.6.25/uml-deal-with-inaccessible-address-space-start.patch
On Sat, 16 Aug 2008 15:32:38 -0700
<[email protected]> wrote:
Hi Greg
while these notifications are very useful in general, I think you want
to exclude lkml as a destination to send them to.....
--
If you want to reach me at my work email, use [email protected]
For development, discussion and tips for power savings,
visit http://www.lesswatts.org
On Sat, Aug 16, 2008 at 03:41:44PM -0700, Arjan van de Ven wrote:
> On Sat, 16 Aug 2008 15:32:38 -0700
> <[email protected]> wrote:
>
>
> Hi Greg
>
> while these notifications are very useful in general, I think you want
> to exclude lkml as a destination to send them to.....
Argh, sorry about that, I should have filtered that address out.
greg k-h