On Mon, Nov 27, 2017 at 11:49:07AM +0100, Ingo Molnar wrote:
> From: Dave Hansen <[email protected]>
>
> Normally, a process has a NULL mm->context.ldt. But, there is a
> syscall for a process to set a new one. If a process does that,
> the LDT be mapped into the user page tables, just like the
> default copy.
>
> The original KAISER patch missed this case.
>
> Signed-off-by: Dave Hansen <[email protected]>
> Signed-off-by: Thomas Gleixner <[email protected]>
> Cc: Andy Lutomirski <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: Brian Gerst <[email protected]>
> Cc: Denys Vlasenko <[email protected]>
> Cc: H. Peter Anvin <[email protected]>
> Cc: Josh Poimboeuf <[email protected]>
> Cc: Linus Torvalds <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Rik van Riel <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Link: https://lkml.kernel.org/r/[email protected]
> Signed-off-by: Ingo Molnar <[email protected]>
> ---
> arch/x86/kernel/ldt.c | 25 ++++++++++++++++++++-----
> 1 file changed, 20 insertions(+), 5 deletions(-)
>
...
> +
> /* The caller must call finalize_ldt_struct on the result. LDT starts
> zeroed. */
> static struct ldt_struct *alloc_ldt_struct(unsigned int num_entries)
> {
> struct ldt_struct *new_ldt;
> unsigned int alloc_size;
> + int ret;
>
> if (num_entries > LDT_ENTRIES)
> return NULL;
> @@ -89,6 +100,12 @@ static struct ldt_struct *alloc_ldt_struct(unsigned int
> num_entries)
> return NULL;
> }
>
> + ret = kaiser_add_mapping((unsigned long)new_ldt->entries, alloc_size,
> + __PAGE_KERNEL | _PAGE_GLOBAL);
This results in:
arch/x86/kernel/ldt.c: In function ‘alloc_ldt_struct’:
arch/x86/kernel/ldt.c:104:6: warning: large integer implicitly truncated to
unsigned type [-Woverflow]
__PAGE_KERNEL | _PAGE_GLOBAL);
^
in ARCH=i386 builds with CONFIG_X86_PAE enabled. See
https://groups.google.com/forum/#!topic/cros-kernel-buildreports/8R41aX07daU
Guenter
