On Sat, Apr 02, 2016 at 07:01:35AM -0700, Andy Lutomirski wrote:
> Now that early_fixup_exception has pt_regs, we can just call
> fixup_exception from it. This will make fancy exception handlers
> work early.
>
> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
> ---
> arch/x86/mm/extable.c | 19 ++-----------------
> 1 file changed, 2 insertions(+), 17 deletions(-)
>
> diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
> index 8997022abebc..50dfe438bd91 100644
> --- a/arch/x86/mm/extable.c
> +++ b/arch/x86/mm/extable.c
> @@ -95,10 +95,6 @@ extern unsigned int early_recursion_flag;
> /* Restricted version used during very early boot */
> void __init early_fixup_exception(struct pt_regs *regs, int trapnr)
> {
> - const struct exception_table_entry *e;
> - unsigned long new_ip;
> - ex_handler_t handler;
> -
> /* Ignore early NMIs. */
> if (trapnr == X86_TRAP_NMI)
> return;
> @@ -109,19 +105,8 @@ void __init early_fixup_exception(struct pt_regs *regs, int trapnr)
> if (regs->cs != __KERNEL_CS)
> goto fail;
>
> - e = search_exception_tables(regs->ip);
> - if (!e)
> - goto fail;
> -
> - new_ip = ex_fixup_addr(e);
> - handler = ex_fixup_handler(e);
> -
> - /* special handling not supported during early boot */
> - if (handler != ex_handler_default)
> - goto fail;
Hold on, what happened to the uaccess handling not being supported
during early boot?
So before Tony changed it, the original code had:
/* Restricted version used during very early boot */
int __init early_fixup_exception(unsigned long *ip)
{
...
- if (fixup->fixup - fixup->insn >= 0x7ffffff0 - 4) {
- /* uaccess handling not supported during early boot */
- return 0;
- }
I'm guessing that wasn't supported early, probably because some stuff
wasn't initialized yet. Our normal, late fixup is by doing:
current_thread_info()->uaccess_err = 1;
and I'm assuming we can't do that early. current_thread_info is probably
not setup yet...
> -
> - regs->ip = new_ip;
> - return;
> + if (fixup_exception(regs, trapnr))
> + return;
So why can we do it now, all of a sudden?
/me is scratching head.
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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