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| author |   Kairui Song <kasong@redhat.com> | 2018-09-27 20:38:45 +0800 |
|---|---|---|
| committer |   Borislav Petkov <bp@suse.de> | 2018-09-27 19:35:03 +0200 |
| commit | bdec8d7fa55e6f5314ed72e5a0b435d90ff90548 (patch) | |
| tree | aaafb2bba10a7d633623bc6304084c16e5d628ce | |
| parent | x86/mm: Expand static page table for fixmap space (diff) | |
| download | linux-dev-bdec8d7fa55e6f5314ed72e5a0b435d90ff90548.tar.xz linux-dev-bdec8d7fa55e6f5314ed72e5a0b435d90ff90548.zip | |
x86/boot: Fix kexec booting failure in the SEV bit detection code
Commit
1958b5fc4010 ("x86/boot: Add early boot support when running with SEV active")
can occasionally cause system resets when kexec-ing a second kernel even
if SEV is not active.
That's because get_sev_encryption_bit() uses 32-bit rIP-relative
addressing to read the value of enc_bit - a variable which caches a
previously detected encryption bit position - but kexec may allocate
the early boot code to a higher location, beyond the 32-bit addressing
limit.
In this case, garbage will be read and get_sev_encryption_bit() will
return the wrong value, leading to accessing memory with the wrong
encryption setting.
Therefore, remove enc_bit, and thus get rid of the need to do 32-bit
rIP-relative addressing in the first place.
[ bp: massage commit message heavily. ]
Fixes: 1958b5fc4010 ("x86/boot: Add early boot support when running with SEV active")
Suggested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Kairui Song <kasong@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: linux-kernel@vger.kernel.org
Cc: tglx@linutronix.de
Cc: mingo@redhat.com
Cc: hpa@zytor.com
Cc: brijesh.singh@amd.com
Cc: kexec@lists.infradead.org
Cc: dyoung@redhat.com
Cc: bhe@redhat.com
Cc: ghook@redhat.com
Link: https://lkml.kernel.org/r/20180927123845.32052-1-kasong@redhat.com
| -rw-r--r-- | arch/x86/boot/compressed/mem_encrypt.S | 19 |
1 files changed, 0 insertions, 19 deletions
diff --git a/arch/x86/boot/compressed/mem_encrypt.S b/arch/x86/boot/compressed/mem_encrypt.S index eaa843a52907..a480356e0ed8 100644 --- a/arch/x86/boot/compressed/mem_encrypt.S +++ b/arch/x86/boot/compressed/mem_encrypt.S @@ -25,20 +25,6 @@ ENTRY(get_sev_encryption_bit) push %ebx push %ecx push %edx - push %edi - - /* - * RIP-relative addressing is needed to access the encryption bit - * variable. Since we are running in 32-bit mode we need this call/pop - * sequence to get the proper relative addressing. - */ - call 1f -1: popl %edi - subl $1b, %edi - - movl enc_bit(%edi), %eax - cmpl $0, %eax - jge .Lsev_exit /* Check if running under a hypervisor */ movl $1, %eax @@ -69,15 +55,12 @@ ENTRY(get_sev_encryption_bit) movl %ebx, %eax andl $0x3f, %eax /* Return the encryption bit location */ - movl %eax, enc_bit(%edi) jmp .Lsev_exit .Lno_sev: xor %eax, %eax - movl %eax, enc_bit(%edi) .Lsev_exit: - pop %edi pop %edx pop %ecx pop %ebx @@ -113,8 +96,6 @@ ENTRY(set_sev_encryption_mask) ENDPROC(set_sev_encryption_mask) .data -enc_bit: - .int 0xffffffff #ifdef CONFIG_AMD_MEM_ENCRYPT .balign 8 |