[PATCH 4/4] efi: Make efi virtual runtime map passing more robust

[Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>]

From: Borislav Petkov <bp-l3A5Bk7waGM@public.gmane.org>

Currently, running SetVirtualAddressMap() and passing the physical
address of the virtual map array was working only by a lucky coincidence
because the memory was present in the EFI page table too. Until Toshi
went and booted this on a big HP box - the krealloc() manner of resizing
the memmap we're doing did allocate from such physical addresses which
were not mapped anymore and boom:

http://lkml.kernel.org/r/1386806463.1791.295.camel-RbGIw1UOYPVo/CpIj0byZw@public.gmane.org

One way to take care of that issue is to reimplement the krealloc thing
but with pages. We start with contiguous pages of order 1, i.e. 2 pages,
and when we deplete that memory (shouldn't happen all that often but you
know firmware) we realloc the next power-of-two pages.

Having the pages, it is much more handy and easy to map them into the
EFI page table with the already existing mapping code which we're using
for building the virtual mappings.

And, it doesn't matter all that much how much pages we've used as we're
freeing them right after they've fulfilled their purpose at the end of
the function anyway.

Reported-by: Toshi Kani <toshi.kani-VXdhtT5mjnY@public.gmane.org>
Signed-off-by: Borislav Petkov <bp-l3A5Bk7waGM@public.gmane.org>
---
 arch/x86/include/asm/efi.h     |  3 +-
 arch/x86/platform/efi/efi.c    | 62 ++++++++++++++++++++++++++++++------------
 arch/x86/platform/efi/efi_32.c |  6 +++-
 arch/x86/platform/efi/efi_64.c | 31 +++++++++++++++++++--
 4 files changed, 80 insertions(+), 22 deletions(-)

diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index 3b978c472d08..0e7973f7492e 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -130,7 +130,8 @@ extern void efi_memory_uc(u64 addr, unsigned long size);
 extern void __init efi_map_region(efi_memory_desc_t *md);
 extern void __init efi_map_region_fixed(efi_memory_desc_t *md);
 extern void efi_sync_low_kernel_mappings(void);
-extern void efi_setup_page_tables(void);
+extern int efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages);
+extern void efi_cleanup_page_tables(unsigned long pa_memmap, unsigned num_pages);
 extern void __init old_map_region(efi_memory_desc_t *md);
 
 struct efi_setup_data {
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index c34be4ce94c9..65a8c969db87 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -948,14 +948,36 @@ static void __init efi_map_regions_fixed(void)
 
 }
 
+static void *realloc_pages(void *old_memmap, int old_shift)
+{
+	void *ret;
+
+	ret = (void *)__get_free_pages(GFP_KERNEL, old_shift + 1);
+	if (!ret)
+		goto out;
+
+	/*
+	 * A first-time allocation doesn't have anything to copy.
+	 */
+	if (!old_memmap)
+		return ret;
+
+	memcpy(ret, old_memmap, PAGE_SIZE << old_shift);
+
+out:
+	__free_pages(old_memmap, old_shift);
+	return ret;
+}
+
 /*
- * Map efi memory ranges for runtime serivce and update new_memmap with virtual
- * addresses.
+ * Map the efi memory ranges of the runtime services and update new_mmap with
+ * virtual addresses.
  */
-static void * __init efi_map_regions(int *count)
+static void * __init efi_map_regions(int *count, int *pg_shift)
 {
+	void *p, *new_memmap = NULL;
+	unsigned long left = 0;
 	efi_memory_desc_t *md;
-	void *p, *tmp, *new_memmap = NULL;
 
 	for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
 		md = p;
@@ -970,20 +992,23 @@ static void * __init efi_map_regions(int *count)
 		efi_map_region(md);
 		get_systab_virt_addr(md);
 
-		tmp = krealloc(new_memmap, (*count + 1) * memmap.desc_size,
-			       GFP_KERNEL);
-		if (!tmp)
-			goto out;
-		new_memmap = tmp;
+		if (left < memmap.desc_size) {
+			new_memmap = realloc_pages(new_memmap, *pg_shift);
+			if (!new_memmap)
+				return NULL;
+
+			left += PAGE_SIZE << *pg_shift;
+			(*pg_shift)++;
+		}
+
 		memcpy(new_memmap + (*count * memmap.desc_size), md,
 		       memmap.desc_size);
+
+		left -= memmap.desc_size;
 		(*count)++;
 	}
 
 	return new_memmap;
-out:
-	kfree(new_memmap);
-	return NULL;
 }
 
 /*
@@ -1009,9 +1034,9 @@ out:
  */
 void __init efi_enter_virtual_mode(void)
 {
-	efi_status_t status;
+	int err, count = 0, pg_shift = 0;
 	void *new_memmap = NULL;
-	int err, count = 0;
+	efi_status_t status;
 
 	efi.systab = NULL;
 
@@ -1028,7 +1053,7 @@ void __init efi_enter_virtual_mode(void)
 		efi_map_regions_fixed();
 	} else {
 		efi_merge_regions();
-		new_memmap = efi_map_regions(&count);
+		new_memmap = efi_map_regions(&count, &pg_shift);
 		if (!new_memmap) {
 			pr_err("Error reallocating memory, EFI runtime non-functional!\n");
 			return;
@@ -1041,7 +1066,9 @@ void __init efi_enter_virtual_mode(void)
 
 	BUG_ON(!efi.systab);
 
-	efi_setup_page_tables();
+	if (efi_setup_page_tables(__pa(new_memmap), 1 << pg_shift))
+		return;
+
 	efi_sync_low_kernel_mappings();
 	dump_pagetable();
 
@@ -1083,7 +1110,8 @@ void __init efi_enter_virtual_mode(void)
 	if (efi_enabled(EFI_OLD_MEMMAP) && (__supported_pte_mask & _PAGE_NX))
 		runtime_code_page_mkexec();
 
-	kfree(new_memmap);
+	efi_cleanup_page_tables(__pa(new_memmap), 1 << pg_shift);
+	__free_pages(new_memmap, pg_shift);
 
 	/* clean DUMMY object */
 	efi.set_variable(efi_dummy_name, &EFI_DUMMY_GUID,
diff --git a/arch/x86/platform/efi/efi_32.c b/arch/x86/platform/efi/efi_32.c
index 249b183cf417..d58a2015e22d 100644
--- a/arch/x86/platform/efi/efi_32.c
+++ b/arch/x86/platform/efi/efi_32.c
@@ -40,7 +40,11 @@
 static unsigned long efi_rt_eflags;
 
 void efi_sync_low_kernel_mappings(void) {}
-void efi_setup_page_tables(void) {}
+int efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
+{
+	return 0;
+}
+void efi_cleanup_page_tables(unsigned long pa_memmap, unsigned num_pages) {}
 
 void __init efi_map_region(efi_memory_desc_t *md)
 {
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 6284f158a47d..3d66844ea156 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -137,12 +137,37 @@ void efi_sync_low_kernel_mappings(void)
 		sizeof(pgd_t) * num_pgds);
 }
 
-void efi_setup_page_tables(void)
+int efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
 {
+	pgd_t *pgd;
+
+	if (efi_enabled(EFI_OLD_MEMMAP))
+		return 0;
+
+	/*
+	 * 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
+	 * and ident-map those pages containing the map before calling
+	 * phys_efi_set_virtual_address_map().
+	 */
+	if (kernel_map_pages_in_pgd(pgd, pa_memmap, pa_memmap, num_pages, _PAGE_NX)) {
+		pr_err("Error ident-mapping new memmap (0x%lx)!\n", pa_memmap);
+		return 1;
+	}
+
 	efi_scratch.efi_pgt = (pgd_t *)(unsigned long)real_mode_header->trampoline_pgd;
+	efi_scratch.use_pgd = true;
 
-	if (!efi_enabled(EFI_OLD_MEMMAP))
-		efi_scratch.use_pgd = true;
+	pgd = __va(efi_scratch.efi_pgt);
+
+	return 0;
+}
+
+void efi_cleanup_page_tables(unsigned long pa_memmap, unsigned num_pages)
+{
+	pgd_t *pgd = (pgd_t *)__va(real_mode_header->trampoline_pgd);
+
+	kernel_unmap_pages_in_pgd(pgd, pa_memmap, num_pages);
 }
 
 static void __init __map_region(efi_memory_desc_t *md, u64 va)
-- 
1.8.5.2.192.g7794a68