[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v4 1/4] x86/boot: Initialise BSS sooner
Allows to call C code earlier. In order to safely call C code we need to setup stack, selectors and BSS. Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxx> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> --- Changes since v1: - improve commit message; - improve some comments; - fix some code style (spacing); - set trampoline_phys as 32 bit value; - use PAGE_SIZE mnemonic instead of 0x1000; - use local label. Changes since v3: - improved comment; - fixed indentation. --- xen/arch/x86/boot/head.S | 77 ++++++++++++++++++++-------------------- 1 file changed, 39 insertions(+), 38 deletions(-) diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S index cfc5a7b47d..267207e5a2 100644 --- a/xen/arch/x86/boot/head.S +++ b/xen/arch/x86/boot/head.S @@ -231,6 +231,27 @@ __efi64_mb2_start: /* VGA is not available on EFI platforms. */ movl $0,vga_text_buffer(%rip) + /* + * Align the stack as UEFI spec requires. Keep it aligned + * before efi_multiboot2() call by pushing/popping even + * numbers of items on it. + */ + and $~15, %rsp + + /* + * Initialize BSS (no nasty surprises!). + * It must be done earlier than in BIOS case + * because efi_multiboot2() touches it. + */ + mov %eax, %edx + lea __bss_start(%rip), %edi + lea __bss_end(%rip), %ecx + sub %edi, %ecx + shr $3, %ecx + xor %eax, %eax + rep stosq + mov %edx, %eax + /* Check for Multiboot2 bootloader. */ cmp $MULTIBOOT2_BOOTLOADER_MAGIC,%eax je .Lefi_multiboot2_proto @@ -321,34 +342,12 @@ __efi64_mb2_start: lea .Lmb2_no_ih(%rip),%r15 jz x86_32_switch - /* - * Align the stack as UEFI spec requires. Keep it aligned - * before efi_multiboot2() call by pushing/popping even - * numbers of items on it. - */ - and $~15,%rsp - /* Save Multiboot2 magic on the stack. */ push %rax /* Save EFI ImageHandle on the stack. */ push %rdi - /* - * Initialize BSS (no nasty surprises!). - * It must be done earlier than in BIOS case - * because efi_multiboot2() touches it. - */ - lea __bss_start(%rip),%edi - lea __bss_end(%rip),%ecx - sub %edi,%ecx - shr $3,%ecx - xor %eax,%eax - rep stosq - - /* Keep the stack aligned. Do not pop a single item off it. */ - mov (%rsp),%rdi - /* * efi_multiboot2() is called according to System V AMD64 ABI: * - IN: %rdi - EFI ImageHandle, %rsi - EFI SystemTable, @@ -434,6 +433,8 @@ __pvh_start: /* Set up stack. */ lea STACK_SIZE - CPUINFO_sizeof + sym_esi(cpu0_stack), %esp + call .Linitialise_bss + mov %ebx, sym_esi(pvh_start_info_pa) /* Force xen console. Will revert to user choice in init code. */ @@ -459,6 +460,20 @@ __pvh_start: #endif /* CONFIG_PVH_GUEST */ +.Linitialise_bss: + /* Initialise the BSS. Preserve %eax (BOOTLOADER_MAGIC). */ + mov %eax, %ebp + + lea sym_esi(__bss_start), %edi + lea sym_esi(__bss_end), %ecx + sub %edi, %ecx + xor %eax, %eax + shr $2, %ecx + rep stosl + + mov %ebp, %eax + ret + __start: cld cli @@ -489,6 +504,8 @@ __start: /* Set up stack. */ lea STACK_SIZE - CPUINFO_sizeof + sym_esi(cpu0_stack), %esp + call .Linitialise_bss + /* Bootloaders may set multiboot{1,2}.mem_lower to a nonzero value. */ xor %edx,%edx @@ -645,22 +662,6 @@ trampoline_setup: * reserved for trampoline code and data. */ - /* - * Do not zero BSS on EFI platform here. - * It was initialized earlier. - */ - cmpb $0, sym_esi(efi_platform) - jnz 1f - - /* Initialise the BSS. */ - lea sym_esi(__bss_start), %edi - lea sym_esi(__bss_end), %ecx - sub %edi,%ecx - xor %eax,%eax - shr $2,%ecx - rep stosl - -1: /* Interrogate CPU extended features via CPUID. */ mov $1, %eax cpuid -- 2.34.1
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