leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

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

Browse Source 
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: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-25-joro@8bytes.org
This commit is contained in:
Joerg Roedel 2020-09-07 15:15:25 +02:00 committed by Borislav Petkov
parent 597cfe4821
commit 69add17a7c
3 changed files with 35 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
arch/x86/boot/compressed/ident_map_64.c
View File

@ -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

6
arch/x86/boot/compressed/misc.h
View File

@ -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 */

14
arch/x86/boot/compressed/sev-es.c
View File

@ -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)