On Fri, Jul 28, 2023 at 11:09:08AM +0200, Ard Biesheuvel wrote:
> diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c
> index 4016444e6788304f..4f50af23a0854f18 100644
> --- a/arch/x86/boot/compressed/pgtable_64.c
> +++ b/arch/x86/boot/compressed/pgtable_64.c
> @@ -101,9 +101,10 @@ static unsigned long find_trampoline_placement(void)
> return bios_start - TRAMPOLINE_32BIT_SIZE;
> }
>
> -asmlinkage void set_paging_levels(void *rmode)
> +asmlinkage void set_paging_levels(void *rmode, void *pgtable)
Please get rid of this silly rmode arg which gets passed in here as
boot_params and then gets assigned to an extern pointer to boot_params.
This is just silly. Just do what the other functions get from %r15 now
- a struct boot_params *bp arg.
But perhaps in a separate patch.
> {
> void (*toggle_la57)(void *trampoline, bool enable_5lvl);
> + void *trampoline_pgtable;
> bool l5_required = false;
>
> /* Initialize boot_params. Required for cmdline_find_option_bool(). */
> @@ -133,7 +134,7 @@ asmlinkage void set_paging_levels(void *rmode)
> * the desired one.
> */
> if (l5_required == !!(native_read_cr4() & X86_CR4_LA57))
> - return;
> + goto out;
>
> trampoline_32bit = (unsigned long *)find_trampoline_placement();
>
> @@ -163,6 +164,8 @@ asmlinkage void set_paging_levels(void *rmode)
> * The new page table will be used by trampoline code for switching
> * from 4- to 5-level paging or vice versa.
> */
> + trampoline_pgtable = trampoline_32bit +
> + TRAMPOLINE_32BIT_PGTABLE_OFFSET / sizeof(unsigned long);
>
> if (l5_required) {
> /*
> @@ -182,31 +185,21 @@ asmlinkage void set_paging_levels(void *rmode)
> * may be above 4G.
> */
> src = *(unsigned long *)__native_read_cr3() & PAGE_MASK;
> - memcpy(trampoline_32bit + TRAMPOLINE_32BIT_PGTABLE_OFFSET / sizeof(unsigned long),
> - (void *)src, PAGE_SIZE);
> + memcpy(trampoline_pgtable, (void *)src, PAGE_SIZE);
> }
>
> toggle_la57(trampoline_32bit, l5_required);
> -}
> -
> -void cleanup_trampoline(void *pgtable)
> -{
> - void *trampoline_pgtable;
> -
> - trampoline_pgtable = trampoline_32bit + TRAMPOLINE_32BIT_PGTABLE_OFFSET / sizeof(unsigned long);
>
> /*
> - * Move the top level page table out of trampoline memory,
> - * if it's there.
> + * Move the top level page table out of trampoline memory.
> */
> - if ((void *)__native_read_cr3() == trampoline_pgtable) {
> - memcpy(pgtable, trampoline_pgtable, PAGE_SIZE);
> - native_write_cr3((unsigned long)pgtable);
> - }
> + memcpy(pgtable, trampoline_pgtable, PAGE_SIZE);
> + native_write_cr3((unsigned long)pgtable);
>
> /* Restore trampoline memory */
> memcpy(trampoline_32bit, trampoline_save, TRAMPOLINE_32BIT_SIZE);
>
> +out:
> /* Initialize variables for 5-level paging */
> #ifdef CONFIG_X86_5LEVEL
> if (__read_cr4() & X86_CR4_LA57) {
> @@ -215,4 +208,5 @@ void cleanup_trampoline(void *pgtable)
> ptrs_per_p4d = 512;
> }
> #endif
> + return;
No need for that one. It'll return without it. :-)
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
