From 6ae28b205b7913e9bdd16243724539143556509d Mon Sep 17 00:00:00 2001 From: Julius Werner Date: Fri, 5 Aug 2016 21:27:47 -0700 Subject: [PATCH] UPSTREAM: libpayload: head.S: Avoid clearing BSS (and heap) again 3 out of 4 architectures currently zero out the payload BSS in early assembly code, which is pointless since the code loading the payload has already done that (with a more efficient memset). ARM64 has never had any code like this and can run just fine without it. This also defeats the new optimization of moving the heap out of the BSS, since all three implementations assume that everything between _edata and _end is BSS. We should just take this out. BUG=None BRANCH=None TEST=None Signed-off-by: Julius Werner Reviewed-on: https://review.coreboot.org/16091 Reviewed-by: Aaron Durbin Reviewed-by: Stefan Reinauer Change-Id: I45cd2dabd94da43ff0f77e990f11c877cee6cda1 Reviewed-on: https://chromium-review.googlesource.com/370697 Commit-Ready: Furquan Shaikh Tested-by: Furquan Shaikh Reviewed-by: Aaron Durbin --- payloads/libpayload/arch/arm/head.S | 19 ------------------- payloads/libpayload/arch/mips/head.S | 10 ---------- payloads/libpayload/arch/x86/head.S | 8 -------- 3 files changed, 37 deletions(-) diff --git a/payloads/libpayload/arch/arm/head.S b/payloads/libpayload/arch/arm/head.S index 788e328322..299faf2c4f 100644 --- a/payloads/libpayload/arch/arm/head.S +++ b/payloads/libpayload/arch/arm/head.S @@ -33,22 +33,6 @@ * Our entry point */ ENTRY(_entry) - - /* TODO: disable interrupts */ - - /* Clear BSS */ - mov r12, #0 - ldr r2, bss_boundaries - ldr r3, bss_boundaries + 4 - cmp r2, r3 - beq no_bss - - sub r3, #4 /* Account for late condition check. */ -loop: - cmp r2, r3 - str r12, [r2], #4 - blt loop -no_bss: /* Save off the location of the coreboot tables */ ldr r1, 1f str r0, [r1] @@ -70,9 +54,6 @@ no_bss: ENDPROC(_entry) .align 4 -bss_boundaries: - .word _edata - .word _end 1: .word cb_header_ptr 2: diff --git a/payloads/libpayload/arch/mips/head.S b/payloads/libpayload/arch/mips/head.S index c143e95844..203e0ae1bf 100644 --- a/payloads/libpayload/arch/mips/head.S +++ b/payloads/libpayload/arch/mips/head.S @@ -74,16 +74,6 @@ _entry: 1: lw $gp, 0($ra) - /* Clear .bss: start_bss = _edata, end_bss = _end */ - la $t0, _edata - sw $zero, ($t0) - la $t1, _end - 4 -clear_bss: - addiu $t0, 4 - sw $zero, ($t0) - bne $t0, $t1, clear_bss - nop - /* Save off the location of the coreboot tables */ la $at, cb_header_ptr sw $a0, 0x00($at) diff --git a/payloads/libpayload/arch/x86/head.S b/payloads/libpayload/arch/x86/head.S index 3dd61336f9..fa9bb7374f 100644 --- a/payloads/libpayload/arch/x86/head.S +++ b/payloads/libpayload/arch/x86/head.S @@ -73,14 +73,6 @@ _init: movl %eax,loader_eax movl %ebx,loader_ebx - /* Clear the bss */ - cld - movl $.bss, %edi - movl $_end, %ecx - subl %edi, %ecx - xor %ax, %ax - rep stosb - /* Setup new stack. */ movl $_stack, %ebx