x86/boot/compressed: Handle unaccepted memory

Firmware is responsible for accepting memory where compressed kernel
image and initrd land. But kernel has to accept memory for decompression
buffer: accept memory just before decompression starts

KASLR allowed to use unaccepted memory for output buffer.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

arch/x86/boot/compressed/bitmap.c

@@ -2,6 +2,48 @@
 /* Taken from lib/string.c */
 
 #include <linux/bitmap.h>
+#include <linux/math.h>
+#include <linux/minmax.h>
+
+unsigned long _find_next_bit(const unsigned long *addr1,
+		const unsigned long *addr2, unsigned long nbits,
+		unsigned long start, unsigned long invert, unsigned long le)
+{
+	unsigned long tmp, mask;
+
+	if (unlikely(start >= nbits))
+		return nbits;
+
+	tmp = addr1[start / BITS_PER_LONG];
+	if (addr2)
+		tmp &= addr2[start / BITS_PER_LONG];
+	tmp ^= invert;
+
+	/* Handle 1st word. */
+	mask = BITMAP_FIRST_WORD_MASK(start);
+	if (le)
+		mask = swab(mask);
+
+	tmp &= mask;
+
+	start = round_down(start, BITS_PER_LONG);
+
+	while (!tmp) {
+		start += BITS_PER_LONG;
+		if (start >= nbits)
+			return nbits;
+
+		tmp = addr1[start / BITS_PER_LONG];
+		if (addr2)
+			tmp &= addr2[start / BITS_PER_LONG];
+		tmp ^= invert;
+	}
+
+	if (le)
+		tmp = swab(tmp);
+
+	return min(start + __ffs(tmp), nbits);
+}
 
 void __bitmap_set(unsigned long *map, unsigned int start, int len)
 {
@@ -22,3 +64,23 @@ void __bitmap_set(unsigned long *map, unsigned int start, int len)
 		*p |= mask_to_set;
 	}
 }
+
+void __bitmap_clear(unsigned long *map, unsigned int start, int len)
+{
+	unsigned long *p = map + BIT_WORD(start);
+	const unsigned int size = start + len;
+	int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
+	unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
+
+	while (len - bits_to_clear >= 0) {
+		*p &= ~mask_to_clear;
+		len -= bits_to_clear;
+		bits_to_clear = BITS_PER_LONG;
+		mask_to_clear = ~0UL;
+		p++;
+	}
+	if (len) {
+		mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
+		*p &= ~mask_to_clear;
+	}
+}

arch/x86/boot/compressed/kaslr.c

@@ -729,10 +729,20 @@ process_efi_entries(unsigned long minimum, unsigned long image_size)
 		 * but in practice there's firmware where using that memory leads
 		 * to crashes.
 		 *
-		 * Only EFI_CONVENTIONAL_MEMORY is guaranteed to be free.
+		 * Only EFI_CONVENTIONAL_MEMORY and EFI_UNACCEPTED_MEMORY (if
+		 * supported) are guaranteed to be free.
 		 */
-		if (md->type != EFI_CONVENTIONAL_MEMORY)
+
+		switch (md->type) {
+		case EFI_CONVENTIONAL_MEMORY:
+			break;
+		case EFI_UNACCEPTED_MEMORY:
+			if (IS_ENABLED(CONFIG_UNACCEPTED_MEMORY))
+				break;
 			continue;
+		default:
+			continue;
+		}
 
 		if (efi_soft_reserve_enabled() &&
 		    (md->attribute & EFI_MEMORY_SP))

arch/x86/boot/compressed/misc.c

@@ -18,6 +18,7 @@
 #include "../string.h"
 #include "../voffset.h"
 #include <asm/bootparam_utils.h>
+#include <asm/unaccepted_memory.h>
 
 /*
  * WARNING!!
@@ -435,6 +436,14 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
 #endif
 
 	debug_putstr("\nDecompressing Linux... ");
+
+	if (IS_ENABLED(CONFIG_UNACCEPTED_MEMORY) &&
+	    boot_params->unaccepted_memory) {
+		debug_putstr("Accepting memory... ");
+		accept_memory((phys_addr_t)output,
+			      (phys_addr_t)output + needed_size);
+	}
+
 	__decompress(input_data, input_len, NULL, NULL, output, output_len,
 			NULL, error);
 	parse_elf(output);

arch/x86/boot/compressed/unaccepted_memory.c

@@ -43,3 +43,16 @@ void mark_unaccepted(struct boot_params *params, u64 start, u64 end)
 	bitmap_set((unsigned long *)params->unaccepted_memory,
 		   start / PMD_SIZE, (end - start) / PMD_SIZE);
 }
+
+void accept_memory(phys_addr_t start, phys_addr_t end)
+{
+	unsigned long *unaccepted_memory;
+	unsigned int rs, re;
+
+	unaccepted_memory = (unsigned long *)boot_params->unaccepted_memory;
+	bitmap_for_each_set_region(unaccepted_memory, rs, re,
+				   start / PMD_SIZE, end / PMD_SIZE) {
+		__accept_memory(rs * PMD_SIZE, re * PMD_SIZE);
+		bitmap_clear(unaccepted_memory, rs, re - rs);
+	}
+}

arch/x86/include/asm/unaccepted_memory.h

@@ -9,4 +9,6 @@ struct boot_params;
 
 void mark_unaccepted(struct boot_params *params, u64 start, u64 num);
 
+void accept_memory(phys_addr_t start, phys_addr_t end);
+
 #endif