[PATCH] x86/kaslr: try process e820 entries if can not get suitable regions from efi

[Lin Feng]

On efi64 x86_64 system, the EFI_CONVENTIONAL_MEMORY regions will not
be mapped when making EFI runtime calls. So kexec-tools can not get
these from /sys/firmware/efi/runtime-map. Then compressed boot os
can not get suitable regions in process_efi_entries and print debug
message as follow:
        Physical KASLR disabled: no suitable memory region!
To enable physical kaslr with kexec, call process_e820_entries when
no suitable regions in efi memmaps.

Signed-off-by: Lin Feng <linfen...@huawei.com>

---

I find a regular of Kernel code and data placement with kexec. It
seems unsafe. The reason is showed above.

I'm not familiar with efi firmware. I wonder if there are some risks
to get regions according to e820 when there is no suitable region
in efi memmaps.
---
 arch/x86/boot/compressed/kaslr.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index b92fffbe761f..dbd7244b71aa 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -685,6 +685,7 @@ process_efi_entries(unsigned long minimum, unsigned long 
image_size)
 {
        struct efi_info *e = &boot_params->efi_info;
        bool efi_mirror_found = false;
+       bool efi_mem_region_found = false;
        struct mem_vector region;
        efi_memory_desc_t *md;
        unsigned long pmap;
@@ -742,12 +743,13 @@ process_efi_entries(unsigned long minimum, unsigned long 
image_size)
                    !(md->attribute & EFI_MEMORY_MORE_RELIABLE))
                        continue;
 
+               efi_mem_region_found = false;
                region.start = md->phys_addr;
                region.size = md->num_pages << EFI_PAGE_SHIFT;
                if (process_mem_region(&region, minimum, image_size))
                        break;
        }
-       return true;
+       return efi_mem_region_found;
 }
 #else
 static inline bool
-- 
2.23.0