From: Janosch Frank <frankja@xxxxxxxxxxxxx>
When doing an IPL normal the memory will not be zeroed and hence the
BSS section can have any value. We need to clear it by ourselves.
Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx>
---
s390x/cstart64.S | 22 ++++++++++++++++++++--
s390x/flat.lds | 2 ++
2 files changed, 22 insertions(+), 2 deletions(-)
diff --git a/s390x/cstart64.S b/s390x/cstart64.S
index 6622633..dedfe80 100644
--- a/s390x/cstart64.S
+++ b/s390x/cstart64.S
@@ -39,7 +39,22 @@ start:
/* setup initial PSW mask + control registers*/
larl %r1, initial_psw
lpswe 0(%r1)
-init_psw_cont:
+clear_bss_start:
+ larl %r2, __bss_start
+ larl %r3, __bss_end
+ slgr %r3, %r2 # Get sizeof bss
+ aghi %r3,-1
+ srlg %r4,%r3,8 # Calc number of 256 byte chunks
+ ltgr %r4,%r4
+ lgr %r1,%r2
+ jz clear_bss_remainder # If none, clear remaining bytes
+clear_bss_loop:
+ xc 0(256,%r1), 0(%r1) # Clear 256 byte chunks via xor
+ la %r1, 256(%r1)
+ brctg %r4, clear_bss_loop
+clear_bss_remainder:
+ larl %r2, memsetxc
+ ex %r3, 0(%r2)
/* setup pgm interrupt handler */
larl %r1, pgm_int_psw
mvc GEN_LC_PGM_NEW_PSW(16), 0(%r1)
@@ -71,6 +86,9 @@ init_psw_cont:
/* call exit() */
j exit
+memsetxc:
+ xc 0(1,%r1),0(%r1)
+
.macro SAVE_REGS
/* save grs 0-15 */
stmg %r0, %r15, GEN_LC_SW_INT_GRS
@@ -159,7 +177,7 @@ svc_int:
.align 8
initial_psw:
- .quad 0x0000000180000000, init_psw_cont
+ .quad 0x0000000180000000, clear_bss_start
pgm_int_psw:
.quad 0x0000000180000000, pgm_int
ext_int_psw:
diff --git a/s390x/flat.lds b/s390x/flat.lds
index 977af7c..403d967 100644
--- a/s390x/flat.lds
+++ b/s390x/flat.lds
@@ -40,7 +40,9 @@ SECTIONS
. = ALIGN(16);
.rodata : { *(.rodata) *(.rodata.*) }
. = ALIGN(16);
+ __bss_start = .;
.bss : { *(.bss) }
+ __bss_end = .;
. = ALIGN(64K);
edata = .;
. += 64K;
--
1.8.3.1
