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Using unitialized BSS data before that point leads to difficult to debug problems. Fix this by moving clear_bss() to as early as possible. Signed-off-by: Brian Gerst --- arch/x86/include/asm/setup.h | 2 -- arch/x86/kernel/head64.c | 12 ------------ arch/x86/kernel/head_64.S | 20 ++++++++++++++++++++ arch/x86/xen/enlighten_pv.c | 2 -- arch/x86/xen/xen-head.S | 5 ++++- 5 files changed, 24 insertions(+), 17 deletions(-) diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h index 914eb32581c7..5534f4aaf73b 100644 --- a/arch/x86/include/asm/setup.h +++ b/arch/x86/include/asm/setup.h @@ -126,8 +126,6 @@ void *extend_brk(size_t size, size_t align); extern void probe_roms(void); -void clear_bss(void); - #ifdef __i386__ asmlinkage void __init __noreturn i386_start_kernel(void); diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index fd28b53dbac5..9f19635c6390 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -172,16 +172,6 @@ void __init do_early_exception(struct pt_regs *regs, int trapnr) early_fixup_exception(regs, trapnr); } -/* Don't add a printk in there. printk relies on the PDA which is not initialized - yet. */ -void __init clear_bss(void) -{ - memset(__bss_start, 0, - (unsigned long) __bss_stop - (unsigned long) __bss_start); - memset(__brk_base, 0, - (unsigned long) __brk_limit - (unsigned long) __brk_base); -} - static unsigned long get_cmd_line_ptr(void) { unsigned long cmd_line_ptr = boot_params.hdr.cmd_line_ptr; @@ -246,8 +236,6 @@ asmlinkage __visible void __init __noreturn x86_64_start_kernel(char * real_mode vmemmap_base = __VMEMMAP_BASE_L5; } - clear_bss(); - /* * This needs to happen *before* kasan_early_init() because latter maps stuff * into that page. diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 7ed5520dd52e..15ef5ea52b9a 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -37,6 +37,8 @@ .code64 SYM_CODE_START_NOALIGN(startup_64) UNWIND_HINT_END_OF_STACK + cld + /* * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0, * and someone has loaded an identity mapped page table @@ -61,6 +63,8 @@ SYM_CODE_START_NOALIGN(startup_64) /* Set up the stack for verify_cpu() */ leaq __top_init_kernel_stack(%rip), %rsp + call clear_bss + /* * Set up GSBASE. * Note that on SMP the boot CPU uses the init data section until @@ -140,6 +144,22 @@ SYM_CODE_START_NOALIGN(startup_64) jmp *.Lcommon_startup_64(%rip) SYM_CODE_END(startup_64) +SYM_FUNC_START(clear_bss) + xorl %eax, %eax + + leaq __bss_start(%rip), %rdi + leaq __bss_stop(%rip), %rcx + subq %rdi, %rcx + rep stosb + + leaq __brk_base(%rip), %rdi + leaq __brk_limit(%rip), %rcx + subq %rdi, %rcx + rep stosb + + RET +SYM_FUNC_END(clear_bss) + __INITRODATA SYM_DATA_LOCAL(.Lcommon_startup_64, .quad common_startup_64) diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c index 2c64b388f616..6aa13d19c0a4 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -1334,8 +1334,6 @@ asmlinkage __visible void __init xen_start_kernel(struct start_info *si) if (!si) return; - clear_bss(); - xen_start_info = si; __text_gen_insn(&early_xen_iret_patch, diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S index 5dad6c51cdc3..9b56659246fe 100644 --- a/arch/x86/xen/xen-head.S +++ b/arch/x86/xen/xen-head.S @@ -31,6 +31,9 @@ SYM_CODE_START(startup_xen) leaq __top_init_kernel_stack(%rip), %rsp + movq %rsi, %r15 + call clear_bss + /* * Set up GSBASE. * Note that, on SMP, the boot cpu uses init data section until @@ -41,7 +44,7 @@ SYM_CODE_START(startup_xen) xorl %edx, %edx wrmsr - mov %rsi, %rdi + mov %r15, %rdi call xen_start_kernel SYM_CODE_END(startup_xen) __FINIT -- 2.55.0