diff options
Diffstat (limited to 'arch/x86/boot/compressed/head_32.S')
| -rw-r--r-- | arch/x86/boot/compressed/head_32.S | 99 |
1 files changed, 34 insertions, 65 deletions
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index 03557f2174bf..659fad53ca82 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -33,32 +33,13 @@ #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, _egot and _end, 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, _egot and _end as - * hidden: + * These symbols needed to be marked as .hidden to prevent the BFD linker from + * generating R_386_32 (rather than R_386_RELATIVE) relocations for them when + * the 32-bit compressed kernel is linked as PIE. This is no longer necessary, + * but it doesn't hurt to keep them .hidden. */ .hidden _bss .hidden _ebss - .hidden _got - .hidden _egot .hidden _end __HEAD @@ -77,10 +58,10 @@ SYM_FUNC_START(startup_32) leal (BP_scratch+4)(%esi), %esp call 1f 1: popl %edx - subl $1b, %edx + addl $_GLOBAL_OFFSET_TABLE_+(.-1b), %edx /* Load new GDT */ - leal gdt(%edx), %eax + leal gdt@GOTOFF(%edx), %eax movl %eax, 2(%eax) lgdt (%eax) @@ -93,14 +74,16 @@ SYM_FUNC_START(startup_32) movl %eax, %ss /* - * %edx contains the address we are loaded at by the boot loader and %ebx - * contains the address where we should move the kernel image temporarily - * for safe in-place decompression. %ebp contains the address that the kernel - * will be decompressed to. + * %edx contains the address we are loaded at by the boot loader (plus the + * offset to the GOT). The below code calculates %ebx to be the address where + * we should move the kernel image temporarily for safe in-place decompression + * (again, plus the offset to the GOT). + * + * %ebp is calculated to be the address that the kernel will be decompressed to. */ #ifdef CONFIG_RELOCATABLE - movl %edx, %ebx + leal startup_32@GOTOFF(%edx), %ebx #ifdef CONFIG_EFI_STUB /* @@ -111,7 +94,7 @@ SYM_FUNC_START(startup_32) * image_offset = startup_32 - image_base * Otherwise image_offset will be zero and has no effect on the calculations. */ - subl image_offset(%edx), %ebx + subl image_offset@GOTOFF(%edx), %ebx #endif movl BP_kernel_alignment(%esi), %eax @@ -128,10 +111,10 @@ SYM_FUNC_START(startup_32) movl %ebx, %ebp // Save the output address for later /* Target address to relocate to for decompression */ addl BP_init_size(%esi), %ebx - subl $_end, %ebx + subl $_end@GOTOFF, %ebx /* Set up the stack */ - leal boot_stack_end(%ebx), %esp + leal boot_stack_end@GOTOFF(%ebx), %esp /* Zero EFLAGS */ pushl $0 @@ -142,8 +125,8 @@ SYM_FUNC_START(startup_32) * where decompression in place becomes safe. */ pushl %esi - leal (_bss-4)(%edx), %esi - leal (_bss-4)(%ebx), %edi + leal (_bss@GOTOFF-4)(%edx), %esi + leal (_bss@GOTOFF-4)(%ebx), %edi movl $(_bss - startup_32), %ecx shrl $2, %ecx std @@ -156,14 +139,14 @@ SYM_FUNC_START(startup_32) * during extract_kernel below. To avoid any issues, repoint the GDTR * to the new copy of the GDT. */ - leal gdt(%ebx), %eax + leal gdt@GOTOFF(%ebx), %eax movl %eax, 2(%eax) lgdt (%eax) /* * Jump to the relocated address. */ - leal .Lrelocated(%ebx), %eax + leal .Lrelocated@GOTOFF(%ebx), %eax jmp *%eax SYM_FUNC_END(startup_32) @@ -173,7 +156,7 @@ SYM_FUNC_START_ALIAS(efi_stub_entry) add $0x4, %esp movl 8(%esp), %esi /* save boot_params pointer */ call efi_main - leal startup_32(%eax), %eax + /* efi_main returns the possibly relocated address of startup_32 */ jmp *%eax SYM_FUNC_END(efi32_stub_entry) SYM_FUNC_END_ALIAS(efi_stub_entry) @@ -186,40 +169,26 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated) * Clear BSS (stack is currently empty) */ xorl %eax, %eax - leal _bss(%ebx), %edi - leal _ebss(%ebx), %ecx + leal _bss@GOTOFF(%ebx), %edi + leal _ebss@GOTOFF(%ebx), %ecx subl %edi, %ecx shrl $2, %ecx rep stosl /* - * Adjust our own GOT - */ - leal _got(%ebx), %edx - leal _egot(%ebx), %ecx -1: - cmpl %ecx, %edx - jae 2f - addl %ebx, (%edx) - addl $4, %edx - jmp 1b -2: - -/* * Do the extraction, and jump to the new kernel.. */ - /* push arguments for extract_kernel: */ - pushl $z_output_len /* decompressed length, end of relocs */ - - 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 extract_kernel /* returns kernel location in %eax */ + /* push arguments for extract_kernel: */ + + pushl output_len@GOTOFF(%ebx) /* decompressed length, end of relocs */ + pushl %ebp /* output address */ + pushl input_len@GOTOFF(%ebx) /* input_len */ + leal input_data@GOTOFF(%ebx), %eax + pushl %eax /* input_data */ + leal boot_heap@GOTOFF(%ebx), %eax + pushl %eax /* heap area */ + pushl %esi /* real mode pointer */ + call extract_kernel /* returns kernel location in %eax */ addl $24, %esp /* |