So far we've counted on QEMU or kvmtool implicitly zeroing all memory.
With our goal of eventually supporting bare-metal targets with
target-efi we should explicitly zero any memory we expect to be zeroed
ourselves. This obviously includes the BSS, but also the bootcpu's
stack, as the bootcpu's thread-info lives in the stack and may get
used in early setup to get the cpu index. Note, this means we still
assume the bootcpu's cpu index to be zero. That assumption can be
removed later.
Cc: Nikos Nikoleris <nikos.nikoleris@xxxxxxx>
Cc: Alexandru Elisei <alexandru.elisei@xxxxxxx>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@xxxxxxx>
Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
---
arm/cstart.S | 20 ++++++++++++++++++++
arm/cstart64.S | 22 +++++++++++++++++++++-
arm/flat.lds | 4 ++++
3 files changed, 45 insertions(+), 1 deletion(-)
diff --git a/arm/cstart.S b/arm/cstart.S
index ef936ae2f874..9eb11ba4dcaf 100644
--- a/arm/cstart.S
+++ b/arm/cstart.S
@@ -15,12 +15,32 @@
#define THREAD_START_SP ((THREAD_SIZE - S_FRAME_SIZE * 8) & ~7)
+.macro zero_range, tmp1, tmp2, tmp3, tmp4
+ mov \tmp3, #0
+ mov \tmp4, #0
+9998: cmp \tmp1, \tmp2
+ beq 9997f
+ strd \tmp3, \tmp4, [\tmp1], #8
+ b 9998b
+9997:
+.endm
+
.arm
.section .init
.globl start
start:
+ /* zero BSS */
+ ldr r4, =bss
+ ldr r5, =ebss
+ zero_range r4, r5, r6, r7
+
+ /* zero stack */
+ ldr r5, =stacktop
+ sub r4, r5, #THREAD_SIZE
+ zero_range r4, r5, r6, r7
+
/*
* set stack, making room at top of stack for cpu0's
* exception stacks. Must start wtih stackptr, not
diff --git a/arm/cstart64.S b/arm/cstart64.S
index 0428014aa58a..2a691f8f5065 100644
--- a/arm/cstart64.S
+++ b/arm/cstart64.S
@@ -12,6 +12,15 @@
#include <asm/processor.h>
#include <asm/page.h>
#include <asm/pgtable-hwdef.h>
+#include <asm/thread_info.h>
+
+.macro zero_range, tmp1, tmp2
+9998: cmp \tmp1, \tmp2
+ b.eq 9997f
+ stp xzr, xzr, [\tmp1], #16
+ b 9998b
+9997:
+.endm
.section .init
@@ -51,7 +60,18 @@ start:
b 1b
1:
- /* set up stack */
+ /* zero BSS */
+ adrp x4, bss
+ add x4, x4, :lo12:bss
+ adrp x5, ebss
+ add x5, x5, :lo12:ebss
+ zero_range x4, x5
+
+ /* zero and set up stack */
+ adrp x5, stacktop
+ add x5, x5, :lo12:stacktop
+ sub x4, x5, #THREAD_SIZE
+ zero_range x4, x5
mov x4, #1
msr spsel, x4
isb
diff --git a/arm/flat.lds b/arm/flat.lds
index 25f8d03cba87..4d43cdfeab41 100644
--- a/arm/flat.lds
+++ b/arm/flat.lds
@@ -17,7 +17,11 @@ SECTIONS
.rodata : { *(.rodata*) }
.data : { *(.data) }
+ . = ALIGN(16);
+ PROVIDE(bss = .);
.bss : { *(.bss) }
+ . = ALIGN(16);
+ PROVIDE(ebss = .);
. = ALIGN(64K);
PROVIDE(edata = .);
--
2.26.3
