x86: cleanup boot-heap usage

The kernel decompressor wrapper uses memory located beyond the
end of the image. This might lead to hard to debug problems,
but even if it can be proven to be safe, it is at the very
least unclean. I don't see any advantages either, unless you
count it not being zeroed out as an advantage. This patch
moves the boot-heap area to the bss segment.

Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

4 files changed, 31 insertions, 22 deletions

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 036e635f18a3..ba7736cf2ec7 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -130,7 +130,7 @@ relocated:
 /*
  * Setup the stack for the decompressor
  */
-        leal stack_end(%ebx), %esp
+        leal boot_stack_end(%ebx), %esp
 
 /*
  * Do the decompression, and jump to the new kernel..
@@ -142,8 +142,8 @@ relocated:
         pushl %eax      # input_len
         leal input_data(%ebx), %eax
         pushl %eax      # input_data
-        leal _end(%ebx), %eax
-        pushl %eax      # end of the image as third argument
+        leal boot_heap(%ebx), %eax
+        pushl %eax      # heap area as third argument
         pushl %esi      # real mode pointer as second arg
         call decompress_kernel
         addl $20, %esp
@@ -181,7 +181,10 @@ relocated:
         jmp *%ebp
 
 .bss
+/* Stack and heap for uncompression */
 .balign 4
-stack:
-        .fill 4096, 1, 0
-stack_end:
+boot_heap:
+        .fill BOOT_HEAP_SIZE, 1, 0
+boot_stack:
+        .fill BOOT_STACK_SIZE, 1, 0
+boot_stack_end:
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index e8657b98c902..7a212a62db36 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -28,6 +28,7 @@
 #include <asm/segment.h>
 #include <asm/pgtable.h>
 #include <asm/page.h>
+#include <asm/boot.h>
 #include <asm/msr.h>
 #include <asm/asm-offsets.h>
 
@@ -62,7 +63,7 @@ startup_32:
         subl    $1b, %ebp
 
 /* setup a stack and make sure cpu supports long mode. */
-        movl    $user_stack_end, %eax
+        movl    $boot_stack_end, %eax
         addl    %ebp, %eax
         movl    %eax, %esp
 
@@ -274,7 +275,7 @@ relocated:
         stosb
 
         /* Setup the stack */
-        leaq    user_stack_end(%rip), %rsp
+        leaq    boot_stack_end(%rip), %rsp
 
         /* zero EFLAGS after setting rsp */
         pushq   $0
@@ -285,7 +286,7 @@ relocated:
  */
         pushq   %rsi                    # Save the real mode argument
         movq    %rsi, %rdi              # real mode address
-        leaq    _heap(%rip), %rsi       # _heap
+        leaq    boot_heap(%rip), %rsi   # malloc area for uncompression
         leaq    input_data(%rip), %rdx  # input_data
         movl    input_len(%rip), %eax
         movq    %rax, %rcx              # input_len
@@ -310,9 +311,12 @@ gdt:
         .quad   0x0080890000000000      /* TS descriptor */
         .quad   0x0000000000000000      /* TS continued */
 gdt_end:
-        .bss
-/* Stack for uncompression */
-        .balign 4
-user_stack:
-        .fill 4096,4,0
-user_stack_end:
+
+.bss
+/* Stack and heap for uncompression */
+.balign 4
+boot_heap:
+        .fill BOOT_HEAP_SIZE, 1, 0
+boot_stack:
+        .fill BOOT_STACK_SIZE, 1, 0
+boot_stack_end:
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index dad4e699f5a3..90456cee47c3 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -217,12 +217,6 @@ static void putstr(const char *);
 static memptr free_mem_ptr;
 static memptr free_mem_end_ptr;
 
-#ifdef CONFIG_X86_64
-#define HEAP_SIZE             0x7000
-#else
-#define HEAP_SIZE             0x4000
-#endif
-
 static char *vidmem;
 static int vidport;
 static int lines, cols;
@@ -449,7 +443,7 @@ asmlinkage void decompress_kernel(void *rmode, memptr heap,
 
         window = output;                /* Output buffer (Normally at 1M) */
         free_mem_ptr     = heap;        /* Heap */
-        free_mem_end_ptr = heap + HEAP_SIZE;
+        free_mem_end_ptr = heap + BOOT_HEAP_SIZE;
         inbuf  = input_data;            /* Input buffer */
         insize = input_len;
         inptr  = 0;
diff --git a/include/asm-x86/boot.h b/include/asm-x86/boot.h
index ed8affbf96cb..2faed7ecb092 100644
--- a/include/asm-x86/boot.h
+++ b/include/asm-x86/boot.h
@@ -17,4 +17,12 @@
                                 + (CONFIG_PHYSICAL_ALIGN - 1)) \
                                 & ~(CONFIG_PHYSICAL_ALIGN - 1))
 
+#ifdef CONFIG_X86_64
+#define BOOT_HEAP_SIZE  0x7000
+#define BOOT_STACK_SIZE 0x4000
+#else
+#define BOOT_HEAP_SIZE  0x4000
+#define BOOT_STACK_SIZE 0x1000
+#endif
+
 #endif /* _ASM_BOOT_H */