If the BSS section is empty, then the function should return.
If one does not check whether the BSS section is empty or not, then there is a
risk of writing 0s outside of BSS section (which may contain critical data).
Fixes: dac84b66cc9a ("xen: arm64: initial build + config changes, start of day
code")
Signed-off-by: Ayan Kumar Halder <ayan.kumar.hal...@amd.com>
---
Changes from :-
v1..v2 - New patch introduced in v3.
v3 - 1. Update the check in arm32 as well.
2. Drop the R-bs.
xen/arch/arm/arm32/head.S | 3 +++
xen/arch/arm/arm64/head.S | 2 ++
2 files changed, 5 insertions(+)
diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
index a96d5d3503..4ff5c220bc 100644
--- a/xen/arch/arm/arm32/head.S
+++ b/xen/arch/arm/arm32/head.S
@@ -185,12 +185,15 @@ zero_bss:
PRINT("- Zero BSS -\r\n")
mov_w r0, __bss_start /* r0 := vaddr(__bss_start) */
mov_w r1, __bss_end /* r1 := vaddr(__bss_end) */
+ cmp r1, r0
+ beq skip_bss
mov r2, #0
1: str r2, [r0], #4
cmp r0, r1
blo 1b
+skip_bss:
mov pc, lr
ENDPROC(zero_bss)
diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
index 14c3720d80..72c7b24498 100644
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -346,6 +346,8 @@ FUNC_LOCAL(zero_bss)
PRINT("- Zero BSS -\r\n")
ldr x0, =__bss_start /* x0 := vaddr(__bss_start) */
ldr x1, =__bss_end /* x1 := vaddr(__bss_end) */
+ cmp x1, x0
+ beq skip_bss
1: str xzr, [x0], #8
cmp x0, x1
--
2.25.1
