diff options
Diffstat (limited to 'arch/x86/boot/compressed/head_32.S')
| -rw-r--r-- | arch/x86/boot/compressed/head_32.S | 50 |
1 files changed, 42 insertions, 8 deletions
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index 8ef964ddc18e..1038524270e7 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -31,6 +31,34 @@ #include <asm/asm-offsets.h> #include <asm/bootparam.h> +/* + * The 32-bit x86 assembler in binutils 2.26 will generate R_386_GOT32X + * relocation to get the symbol address in PIC. When the compressed x86 + * kernel isn't built as PIC, the linker optimizes R_386_GOT32X + * relocations to their fixed symbol addresses. However, when the + * compressed x86 kernel is loaded at a different address, it leads + * to the following load failure: + * + * Failed to allocate space for phdrs + * + * during the decompression stage. + * + * If the compressed x86 kernel is relocatable at run-time, it should be + * compiled with -fPIE, instead of -fPIC, if possible and should be built as + * Position Independent Executable (PIE) so that linker won't optimize + * R_386_GOT32X relocation to its fixed symbol address. Older + * linkers generate R_386_32 relocations against locally defined symbols, + * _bss, _ebss, _got and _egot, in PIE. It isn't wrong, just less + * optimal than R_386_RELATIVE. But the x86 kernel fails to properly handle + * R_386_32 relocations when relocating the kernel. To generate + * R_386_RELATIVE relocations, we mark _bss, _ebss, _got and _egot as + * hidden: + */ + .hidden _bss + .hidden _ebss + .hidden _got + .hidden _egot + __HEAD ENTRY(startup_32) #ifdef CONFIG_EFI_STUB @@ -148,7 +176,9 @@ preferred_addr: 1: /* Target address to relocate to for decompression */ - addl $z_extract_offset, %ebx + movl BP_init_size(%esi), %eax + subl $_end, %eax + addl %eax, %ebx /* Set up the stack */ leal boot_stack_end(%ebx), %esp @@ -205,24 +235,28 @@ relocated: 2: /* - * Do the decompression, and jump to the new kernel.. + * Do the extraction, and jump to the new kernel.. */ - /* push arguments for decompress_kernel: */ - pushl $z_run_size /* size of kernel with .bss and .brk */ + /* push arguments for extract_kernel: */ pushl $z_output_len /* decompressed length, end of relocs */ - leal z_extract_offset_negative(%ebx), %ebp + + movl BP_init_size(%esi), %eax + subl $_end, %eax + movl %ebx, %ebp + subl %eax, %ebp pushl %ebp /* output address */ + pushl $z_input_len /* input_len */ leal input_data(%ebx), %eax pushl %eax /* input_data */ leal boot_heap(%ebx), %eax pushl %eax /* heap area */ pushl %esi /* real mode pointer */ - call decompress_kernel /* returns kernel location in %eax */ - addl $28, %esp + call extract_kernel /* returns kernel location in %eax */ + addl $24, %esp /* - * Jump to the decompressed kernel. + * Jump to the extracted kernel. */ xorl %ebx, %ebx jmp *%eax |