diff options
Diffstat (limited to 'arch/x86/boot/compressed/head_32.S')
| -rw-r--r-- | arch/x86/boot/compressed/head_32.S | 173 |
1 files changed, 88 insertions, 85 deletions
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index 73f17d0544dd..3b354eb9516d 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -33,51 +33,19 @@ #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: + * 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 SYM_FUNC_START(startup_32) cld - /* - * Test KEEP_SEGMENTS flag to see if the bootloader is asking - * us to not reload segments - */ - testb $KEEP_SEGMENTS, BP_loadflags(%esi) - jnz 1f - cli - movl $__BOOT_DS, %eax - movl %eax, %ds - movl %eax, %es - movl %eax, %fs - movl %eax, %gs - movl %eax, %ss -1: /* * Calculate the delta between where we were compiled to run @@ -89,35 +57,64 @@ SYM_FUNC_START(startup_32) */ leal (BP_scratch+4)(%esi), %esp call 1f -1: popl %ebp - subl $1b, %ebp +1: popl %edx + addl $_GLOBAL_OFFSET_TABLE_+(.-1b), %edx + + /* Load new GDT */ + leal gdt@GOTOFF(%edx), %eax + movl %eax, 2(%eax) + lgdt (%eax) + + /* Load segment registers with our descriptors */ + movl $__BOOT_DS, %eax + movl %eax, %ds + movl %eax, %es + movl %eax, %fs + movl %eax, %gs + movl %eax, %ss /* - * %ebp 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. + * %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 %ebp, %ebx + leal startup_32@GOTOFF(%edx), %ebx + +#ifdef CONFIG_EFI_STUB +/* + * If we were loaded via the EFI LoadImage service, startup_32() will be at an + * offset to the start of the space allocated for the image. efi_pe_entry() will + * set up image_offset to tell us where the image actually starts, so that we + * can use the full available buffer. + * image_offset = startup_32 - image_base + * Otherwise image_offset will be zero and has no effect on the calculations. + */ + subl image_offset@GOTOFF(%edx), %ebx +#endif + movl BP_kernel_alignment(%esi), %eax decl %eax addl %eax, %ebx notl %eax andl %eax, %ebx cmpl $LOAD_PHYSICAL_ADDR, %ebx - jge 1f + jae 1f #endif movl $LOAD_PHYSICAL_ADDR, %ebx 1: + movl %ebx, %ebp // Save the output address for later /* Target address to relocate to for decompression */ - movl BP_init_size(%esi), %eax - subl $_end, %eax - addl %eax, %ebx + addl BP_init_size(%esi), %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 @@ -128,8 +125,8 @@ SYM_FUNC_START(startup_32) * where decompression in place becomes safe. */ pushl %esi - leal (_bss-4)(%ebp), %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 @@ -137,24 +134,31 @@ SYM_FUNC_START(startup_32) cld popl %esi + /* + * The GDT may get overwritten either during the copy we just did or + * during extract_kernel below. To avoid any issues, repoint the GDTR + * to the new copy of the GDT. + */ + 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) #ifdef CONFIG_EFI_STUB SYM_FUNC_START(efi32_stub_entry) -SYM_FUNC_START_ALIAS(efi_stub_entry) add $0x4, %esp + movl 8(%esp), %esi /* save boot_params pointer */ call efi_main - movl %eax, %esi - movl BP_code32_start(%esi), %eax - 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) +SYM_FUNC_ALIAS(efi_stub_entry, efi32_stub_entry) #endif .text @@ -164,42 +168,26 @@ 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 */ - - leal _end(%ebx), %eax - subl BP_init_size(%esi), %eax - pushl %eax /* 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 /* @@ -209,6 +197,21 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated) jmp *%eax SYM_FUNC_END(.Lrelocated) + .data + .balign 8 +SYM_DATA_START_LOCAL(gdt) + .word gdt_end - gdt - 1 + .long 0 + .word 0 + .quad 0x0000000000000000 /* Reserved */ + .quad 0x00cf9a000000ffff /* __KERNEL_CS */ + .quad 0x00cf92000000ffff /* __KERNEL_DS */ +SYM_DATA_END_LABEL(gdt, SYM_L_LOCAL, gdt_end) + +#ifdef CONFIG_EFI_STUB +SYM_DATA(image_offset, .long 0) +#endif + /* * Stack and heap for uncompression */ |