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>

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 036e635..ba7736c 100644 (file)
--- 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 e8657b9..7a212a6 100644 (file)
--- 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 dad4e69..90456ce 100644 (file)
--- 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 ed8affb..2faed7e 100644 (file)
--- 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 */