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Commit 03781e40 authored by Sai Praneeth's avatar Sai Praneeth Committed by Ingo Molnar
Browse files

x86/efi: Use efi_switch_mm() rather than manually twiddling with %cr3 



Use helper function efi_switch_mm() to switch to/from efi_mm when
invoking any UEFI runtime services.

Likewise, we need to switch back to previous mm (mm context stolen
by efi_mm) after the above calls return successfully. We can use
efi_switch_mm() helper function only with x86_64 kernel and
"efi=old_map" disabled because, x86_32 and efi=old_map do not use
efi_pgd, rather they use swapper_pg_dir.

Tested-by: default avatarBhupesh Sharma <bhsharma@redhat.com>
[ardb: add #include of sched/task.h for task_lock/_unlock]
Signed-off-by: default avatarSai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: default avatarMatt Fleming <matt@codeblueprint.co.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Lee, Chun-Yi <jlee@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-efi@vger.kernel.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 3ede3417

arch/x86/include/asm/efi.h

+10 −15
Original line number Diff line number Diff line
@@ -70,14 +70,13 @@ extern asmlinkage u64 efi_call(void *fp, ...); 
#define efi_call_phys(f, args...)		efi_call((f), args)



/*

 * Scratch space used for switching the pagetable in the EFI stub

 * struct efi_scratch - Scratch space used while switching to/from efi_mm

 * @phys_stack: stack used during EFI Mixed Mode

 * @prev_mm:    store/restore stolen mm_struct while switching to/from efi_mm

 */

struct efi_scratch {

	u64	r15;

	u64	prev_cr3;

	pgd_t	*efi_pgt;

	bool	use_pgd;

	u64			phys_stack;

	struct mm_struct	*prev_mm;

} __packed;



#define arch_efi_call_virt_setup()					\
@@ -87,11 +86,8 @@ struct efi_scratch { 
	__kernel_fpu_begin();						\

	firmware_restrict_branch_speculation_start();			\

									\

	if (efi_scratch.use_pgd) {					\

		efi_scratch.prev_cr3 = __read_cr3();			\

		write_cr3((unsigned long)efi_scratch.efi_pgt);		\

		__flush_tlb_all();					\

	}								\

	if (!efi_enabled(EFI_OLD_MEMMAP))				\

		efi_switch_mm(&efi_mm);					\

})



#define arch_efi_call_virt(p, f, args...)				\
@@ -99,10 +95,8 @@ struct efi_scratch { 


#define arch_efi_call_virt_teardown()					\

({									\

	if (efi_scratch.use_pgd) {					\

		write_cr3(efi_scratch.prev_cr3);			\

		__flush_tlb_all();					\

	}								\

	if (!efi_enabled(EFI_OLD_MEMMAP))				\

		efi_switch_mm(efi_scratch.prev_mm);			\

									\

	firmware_restrict_branch_speculation_end();			\

	__kernel_fpu_end();						\
@@ -145,6 +139,7 @@ extern void __init efi_dump_pagetable(void); 
extern void __init efi_apply_memmap_quirks(void);

extern int __init efi_reuse_config(u64 tables, int nr_tables);

extern void efi_delete_dummy_variable(void);

extern void efi_switch_mm(struct mm_struct *mm);



struct efi_setup_data {

	u64 fw_vendor;

arch/x86/platform/efi/efi_64.c

+22 −19
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ 
#include <linux/slab.h>

#include <linux/ucs2_string.h>

#include <linux/mem_encrypt.h>

#include <linux/sched/task.h>



#include <asm/setup.h>

#include <asm/page.h>
@@ -82,9 +83,8 @@ pgd_t * __init efi_call_phys_prolog(void) 
	int n_pgds, i, j;



	if (!efi_enabled(EFI_OLD_MEMMAP)) {

		save_pgd = (pgd_t *)__read_cr3();

		write_cr3((unsigned long)efi_scratch.efi_pgt);

		goto out;

		efi_switch_mm(&efi_mm);

		return NULL;

	}



	early_code_mapping_set_exec(1);
@@ -156,8 +156,7 @@ void __init efi_call_phys_epilog(pgd_t *save_pgd) 
	pud_t *pud;



	if (!efi_enabled(EFI_OLD_MEMMAP)) {

		write_cr3((unsigned long)save_pgd);

		__flush_tlb_all();

		efi_switch_mm(efi_scratch.prev_mm);

		return;

	}
@@ -347,13 +346,6 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages) 
	if (efi_enabled(EFI_OLD_MEMMAP))

		return 0;



	/*

	 * Since the PGD is encrypted, set the encryption mask so that when

	 * this value is loaded into cr3 the PGD will be decrypted during

	 * the pagetable walk.

	 */

	efi_scratch.efi_pgt = (pgd_t *)__sme_pa(pgd);



	/*

	 * It can happen that the physical address of new_memmap lands in memory

	 * which is not mapped in the EFI page table. Therefore we need to go
@@ -367,8 +359,6 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages) 
		return 1;

	}



	efi_scratch.use_pgd = true;



	/*

	 * Certain firmware versions are way too sentimential and still believe

	 * they are exclusive and unquestionable owners of the first physical page,
@@ -627,6 +617,22 @@ void __init efi_dump_pagetable(void) 
#endif

}



/*

 * Makes the calling thread switch to/from efi_mm context. Can be used

 * for SetVirtualAddressMap() i.e. current->active_mm == init_mm as well

 * as during efi runtime calls i.e current->active_mm == current_mm.

 * We are not mm_dropping()/mm_grabbing() any mm, because we are not

 * losing/creating any references.

 */

void efi_switch_mm(struct mm_struct *mm)

{

	task_lock(current);

	efi_scratch.prev_mm = current->active_mm;

	current->active_mm = mm;

	switch_mm(efi_scratch.prev_mm, mm, NULL);

	task_unlock(current);

}



#ifdef CONFIG_EFI_MIXED

extern efi_status_t efi64_thunk(u32, ...);
@@ -680,16 +686,13 @@ efi_status_t efi_thunk_set_virtual_address_map( 
	efi_sync_low_kernel_mappings();

	local_irq_save(flags);



	efi_scratch.prev_cr3 = __read_cr3();

	write_cr3((unsigned long)efi_scratch.efi_pgt);

	__flush_tlb_all();

	efi_switch_mm(&efi_mm);



	func = (u32)(unsigned long)phys_set_virtual_address_map;

	status = efi64_thunk(func, memory_map_size, descriptor_size,

			     descriptor_version, virtual_map);



	write_cr3(efi_scratch.prev_cr3);

	__flush_tlb_all();

	efi_switch_mm(efi_scratch.prev_mm);

	local_irq_restore(flags);



	return status;

arch/x86/platform/efi/efi_thunk_64.S

+1 −1
Original line number Diff line number Diff line
@@ -33,7 +33,7 @@ ENTRY(efi64_thunk) 
	 * Switch to 1:1 mapped 32-bit stack pointer.

	 */

	movq	%rsp, efi_saved_sp(%rip)

	movq	efi_scratch+25(%rip), %rsp

	movq	efi_scratch(%rip), %rsp



	/*

	 * Calculate the physical address of the kernel text.