Commit 69add17a authored by Joerg Roedel's avatar Joerg Roedel Committed by Borislav Petkov
Browse files

x86/boot/compressed/64: Unmap GHCB page before booting the kernel 



Force a page-fault on any further accesses to the GHCB page when they
shouldn't happen anymore. This will catch any bugs where a #VC exception
is raised even though none is expected anymore.

Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-25-joro@8bytes.org
parent 597cfe48

arch/x86/boot/compressed/ident_map_64.c

+15 −2
Original line number Diff line number Diff line
@@ -298,6 +298,11 @@ int set_page_encrypted(unsigned long address) 
	return set_clr_page_flags(&mapping_info, address, _PAGE_ENC, 0);

}



int set_page_non_present(unsigned long address)

{

	return set_clr_page_flags(&mapping_info, address, 0, _PAGE_PRESENT);

}



static void do_pf_error(const char *msg, unsigned long error_code,

			unsigned long address, unsigned long ip)

{
@@ -316,8 +321,14 @@ static void do_pf_error(const char *msg, unsigned long error_code, 


void do_boot_page_fault(struct pt_regs *regs, unsigned long error_code)

{

	unsigned long address = native_read_cr2() & PMD_MASK;

	unsigned long end = address + PMD_SIZE;

	unsigned long address = native_read_cr2();

	unsigned long end;

	bool ghcb_fault;



	ghcb_fault = sev_es_check_ghcb_fault(address);



	address   &= PMD_MASK;

	end        = address + PMD_SIZE;



	/*

	 * Check for unexpected error codes. Unexpected are:
@@ -327,6 +338,8 @@ void do_boot_page_fault(struct pt_regs *regs, unsigned long error_code) 
	 */

	if (error_code & (X86_PF_PROT | X86_PF_USER | X86_PF_RSVD))

		do_pf_error("Unexpected page-fault:", error_code, address, regs->ip);

	else if (ghcb_fault)

		do_pf_error("Page-fault on GHCB page:", error_code, address, regs->ip);



	/*

	 * Error code is sane - now identity map the 2M region around

arch/x86/boot/compressed/misc.h

+6 −0
Original line number Diff line number Diff line
@@ -100,6 +100,7 @@ static inline void choose_random_location(unsigned long input, 
#ifdef CONFIG_X86_64

extern int set_page_decrypted(unsigned long address);

extern int set_page_encrypted(unsigned long address);

extern int set_page_non_present(unsigned long address);

extern unsigned char _pgtable[];

#endif
@@ -117,8 +118,13 @@ void set_sev_encryption_mask(void); 


#ifdef CONFIG_AMD_MEM_ENCRYPT

void sev_es_shutdown_ghcb(void);

extern bool sev_es_check_ghcb_fault(unsigned long address);

#else

static inline void sev_es_shutdown_ghcb(void) { }

static inline bool sev_es_check_ghcb_fault(unsigned long address)

{

	return false;

}

#endif



/* acpi.c */

arch/x86/boot/compressed/sev-es.c

+14 −0
Original line number Diff line number Diff line
@@ -121,6 +121,20 @@ void sev_es_shutdown_ghcb(void) 
	 */

	if (set_page_encrypted((unsigned long)&boot_ghcb_page))

		error("Can't map GHCB page encrypted");



	/*

	 * GHCB page is mapped encrypted again and flushed from the cache.

	 * Mark it non-present now to catch bugs when #VC exceptions trigger

	 * after this point.

	 */

	if (set_page_non_present((unsigned long)&boot_ghcb_page))

		error("Can't unmap GHCB page");

}



bool sev_es_check_ghcb_fault(unsigned long address)

{

	/* Check whether the fault was on the GHCB page */

	return ((address & PAGE_MASK) == (unsigned long)&boot_ghcb_page);

}



void do_boot_stage2_vc(struct pt_regs *regs, unsigned long exit_code)

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