| Message ID | 20181205153918.29480-5-frankja@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | 390x: Add cross hypervisor and disk boot | expand |
On 05.12.18 16:39, Janosch Frank wrote: > 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@linux.ibm.com> > --- > s390x/cstart64.S | 23 ++++++++++++++++++++++- > s390x/flat.lds | 2 ++ > 2 files changed, 24 insertions(+), 1 deletion(-) > > diff --git a/s390x/cstart64.S b/s390x/cstart64.S > index 7886f35..0246e18 100644 > --- a/s390x/cstart64.S > +++ b/s390x/cstart64.S > @@ -37,6 +37,24 @@ start: > /* setup initial PSW mask + control registers*/ > larl %r1, initial_psw > lpswe 0(%r1) > +init_clear_bss: > + larl %r2, __bss_start > + larl %r3, __bss_end > + slgr %r3, %r2 # Get sizeof bss > + ltgr %r3,%r3 # bss empty?> + jz init_psw_cont # Yes, jump to init_psw_cont do we actually need these two instructions? If we should ever not have a bss, things are already pretty shaky :D (we could even enforce a BSS size > 0 in flat.lds) > + aghi %r3,-1 > + srlg %r4,%r3,8 # Calc number of 256 byte chunks > + ltgr %r4,%r4 > + lgr %r1,%r2 > + jz remainder # If none, clear remaining bytes > +loop: > + xc 0(256,%r1), 0(%r1) # Clear 256 byte chunks via xor > + la %r1, 256(%r1) > + brctg %r4, loop > +remainder: > + larl %r2, memsetxc > + ex %r3, 0(%r2) > init_psw_cont: > /* setup pgm interrupt handler */ > larl %r1, pgm_int_psw > @@ -69,6 +87,9 @@ 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 > @@ -157,7 +178,7 @@ svc_int: > > .align 8 > initial_psw: > - .quad 0x0000000180000000, init_psw_cont > + .quad 0x0000000180000000, init_clear_bss > pgm_int_psw: > .quad 0x0000000180000000, pgm_int > ext_int_psw: > diff --git a/s390x/flat.lds b/s390x/flat.lds > index 7cfd9f9..fb229ce 100644 > --- a/s390x/flat.lds > +++ b/s390x/flat.lds > @@ -35,7 +35,9 @@ SECTIONS > . = ALIGN(16); > .rodata : { *(.rodata) *(.rodata.*) } > . = ALIGN(16); > + __bss_start = .; > .bss : { *(.bss) } > + __bss_end = .; > . = ALIGN(64K); > edata = .; > . += 64K; >
diff --git a/s390x/cstart64.S b/s390x/cstart64.S index 7886f35..0246e18 100644 --- a/s390x/cstart64.S +++ b/s390x/cstart64.S @@ -37,6 +37,24 @@ start: /* setup initial PSW mask + control registers*/ larl %r1, initial_psw lpswe 0(%r1) +init_clear_bss: + larl %r2, __bss_start + larl %r3, __bss_end + slgr %r3, %r2 # Get sizeof bss + ltgr %r3,%r3 # bss empty? + jz init_psw_cont # Yes, jump to init_psw_cont + aghi %r3,-1 + srlg %r4,%r3,8 # Calc number of 256 byte chunks + ltgr %r4,%r4 + lgr %r1,%r2 + jz remainder # If none, clear remaining bytes +loop: + xc 0(256,%r1), 0(%r1) # Clear 256 byte chunks via xor + la %r1, 256(%r1) + brctg %r4, loop +remainder: + larl %r2, memsetxc + ex %r3, 0(%r2) init_psw_cont: /* setup pgm interrupt handler */ larl %r1, pgm_int_psw @@ -69,6 +87,9 @@ 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 @@ -157,7 +178,7 @@ svc_int: .align 8 initial_psw: - .quad 0x0000000180000000, init_psw_cont + .quad 0x0000000180000000, init_clear_bss pgm_int_psw: .quad 0x0000000180000000, pgm_int ext_int_psw: diff --git a/s390x/flat.lds b/s390x/flat.lds index 7cfd9f9..fb229ce 100644 --- a/s390x/flat.lds +++ b/s390x/flat.lds @@ -35,7 +35,9 @@ SECTIONS . = ALIGN(16); .rodata : { *(.rodata) *(.rodata.*) } . = ALIGN(16); + __bss_start = .; .bss : { *(.bss) } + __bss_end = .; . = ALIGN(64K); edata = .; . += 64K;
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@linux.ibm.com> --- s390x/cstart64.S | 23 ++++++++++++++++++++++- s390x/flat.lds | 2 ++ 2 files changed, 24 insertions(+), 1 deletion(-)