[PATCH v2] ppc: use rfid when running under a CPU from the 970 family.

[Cédric Le Goater]

A recent attempt to restrict the use of rfi on 64bit cpus in qemu
broke 32bit OpenBIOS when run under a 970.

This patches memory to replace rfi instructions with rfid in the
vector code.

Signed-off-by: Cédric Le Goater 
Suggested-by: Alexander Graf 
---

Tested on qemu.

arch/ppc/qemu/ofmem.c |   24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

Index: openbios.git/arch/ppc/qemu/ofmem.c
===================================================================
--- openbios.git.orig/arch/ppc/qemu/ofmem.c
+++ openbios.git/arch/ppc/qemu/ofmem.c
@@ -478,6 +478,26 @@ isi_exception(void)
     hash_page(nip, phys, mode);
 }

+/* When running on ppc64, we cannot use rfi anymore. Let's patch the
+ * vectors to use rfid instead.
+ */
+#define RFI     0x4c000064
+#define RFID    0x4c000024
+
+static void patch_rfi(char *from, uint32_t len)
+{
+    int i;
+
+    for (i = 0; i < len; i += 4)  {
+        uint32_t* addr = (uint32_t *) (from + i);
+        if (*addr == RFI)
+            *addr = RFID;
+    }
+    flush_icache_range(from, from + len);
+}
+
+extern char __vectors[];
+extern char __vectors_end[];

/************************************************************************/
 /*	init / cleanup							*/
@@ -532,6 +552,10 @@ setup_mmu(unsigned long ramsize)

memcpy((void *)get_rom_base(), (void *)OF_CODE_START, OF_CODE_SIZE);

+    if (is_ppc64()) {
+        patch_rfi(0x0, (uint32_t) __vectors_end - (uint32_t) __vectors);
+    }
+
     /* Enable MMU */

mtmsr(mfmsr() | MSR_IR | MSR_DR);

[Alexander Graf]

> Am 21.06.2016 um 23:36 schrieb Cédric Le Goater :
>
> A recent attempt to restrict the use of rfi on 64bit cpus in qemu
> broke 32bit OpenBIOS when run under a 970.
>
> This patches memory to replace rfi instructions with rfid in the
> vector code.
>
> Signed-off-by: Cédric Le Goater 
> Suggested-by: Alexander Graf
>
> Tested on qemu.
>
> arch/ppc/qemu/ofmem.c |   24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
> Index: openbios.git/arch/ppc/qemu/ofmem.c
>
> --- openbios.git.orig/arch/ppc/qemu/ofmem.c
> +++ openbios.git/arch/ppc/qemu/ofmem.c
> @@ -478,6 +478,26 @@ isi_exception(void)
>     hash_page(nip, phys, mode);
> }
>
> +/* When running on ppc64, we cannot use rfi anymore. Let's patch the
> vectors to use rfid instead.
> */
>
> +#define RFI     0x4c000064
> +#define RFID    0x4c000024
>
> +static void patch_rfi(char *from, uint32_t len)
> +{
> int i;
> for (i = 0; i < len; i += 4)  {
>    uint32_t* addr = (uint32_t *) (from + i);

If you use a uint32* here you can just increment by 1 ...
>    if (*addr == RFI)
>        *addr = RFID;
> }
> flush_icache_range(from, from + len);
>
> +}
>
> +extern char __vectors[];
> +extern char __vectors_end[];

And in fact you can just loop from vectors until ptr==vectors_end.

uint32_t *ptr;

for (ptr = __vectors; ptr != __vectors_end; ptr++)
> /************************************************************************/
> /*    init / cleanup                            */
> @@ -532,6 +552,10 @@ setup_mmu(unsigned long ramsize)
> memcpy((void *)get_rom_base(), (void *)OF_CODE_START, OF_CODE_SIZE);
>
> if (is_ppc64()) {
>    patch_rfi(0x0, (uint32_t) __vectors_end - (uint32_t) __vectors);
> }

Just fold all of this together. Make patch_rfi have no parameters and just call it unconditionally. Then check for ppc64 in there.

Alex
> /* Enable MMU */
>
> mtmsr(mfmsr() | MSR_IR | MSR_DR);

[Cédric Le Goater]

On 06/22/2016 06:50 AM, Alexander Graf wrote:
> > Am 21.06.2016 um 23:36 schrieb Cédric Le Goater :
> >
> > A recent attempt to restrict the use of rfi on 64bit cpus in qemu
> > broke 32bit OpenBIOS when run under a 970.
> >
> > This patches memory to replace rfi instructions with rfid in the
> > vector code.
> >
> > Signed-off-by: Cédric Le Goater 
> > Suggested-by: Alexander Graf
> >
> > Tested on qemu.
> >
> > arch/ppc/qemu/ofmem.c |   24 ++++++++++++++++++++++++
> > 1 file changed, 24 insertions(+)
> > Index: openbios.git/arch/ppc/qemu/ofmem.c
> >
> > --- openbios.git.orig/arch/ppc/qemu/ofmem.c
> > +++ openbios.git/arch/ppc/qemu/ofmem.c
> > @@ -478,6 +478,26 @@ isi_exception(void)
> >     hash_page(nip, phys, mode);
> > }
> >
> > +/* When running on ppc64, we cannot use rfi anymore. Let's patch the
> > vectors to use rfid instead.
> > */
> >
> > +#define RFI     0x4c000064
> > +#define RFID    0x4c000024
> >
> > +static void patch_rfi(char *from, uint32_t len)
> > +{
> > int i;
> > for (i = 0; i < len; i += 4)  {
> >    uint32_t* addr = (uint32_t *) (from + i);
>
> If you use a uint32* here you can just increment by 1 ...

yes. I tried a couple of versions and that was the most friendly for the
flush_icache_range.
> >    if (*addr == RFI)
> >        *addr = RFID;
> > }
> > flush_icache_range(from, from + len);
> >
> > +}
> >
> > +extern char __vectors[];
> > +extern char __vectors_end[];
>
> And in fact you can just loop from vectors until ptr==vectors_end.
>
> uint32_t *ptr;
>
> for (ptr = __vectors; ptr != __vectors_end; ptr++)
> > /************************************************************************/
> > /*    init / cleanup                            */
> > @@ -532,6 +552,10 @@ setup_mmu(unsigned long ramsize)
> > memcpy((void *)get_rom_base(), (void *)OF_CODE_START, OF_CODE_SIZE);
> >
> > if (is_ppc64()) {
> >    patch_rfi(0x0, (uint32_t) __vectors_end - (uint32_t) __vectors);
> > }
>
> Just fold all of this together. Make patch_rfi have no parameters and just call it unconditionally. Then check for ppc64 in there.

ok. v3 on the way.

Thanks,

C.
> Alex
> > /* Enable MMU */
> >
> > mtmsr(mfmsr() | MSR_IR | MSR_DR);

[Alexander Graf]

> Am 22.06.2016 um 08:42 schrieb Cédric Le Goater :
> > On 06/22/2016 06:50 AM, Alexander Graf wrote:
> > > Am 21.06.2016 um 23:36 schrieb Cédric Le Goater :
> > >
> > > A recent attempt to restrict the use of rfi on 64bit cpus in qemu
> > > broke 32bit OpenBIOS when run under a 970.
> > >
> > > This patches memory to replace rfi instructions with rfid in the
> > > vector code.
> > >
> > > Signed-off-by: Cédric Le Goater 
> > > Suggested-by: Alexander Graf
> > >
> > > Tested on qemu.
> > >
> > > arch/ppc/qemu/ofmem.c |   24 ++++++++++++++++++++++++
> > > 1 file changed, 24 insertions(+)
> > > Index: openbios.git/arch/ppc/qemu/ofmem.c
> > >
> > > --- openbios.git.orig/arch/ppc/qemu/ofmem.c
> > > +++ openbios.git/arch/ppc/qemu/ofmem.c
> > > @@ -478,6 +478,26 @@ isi_exception(void)
> > >    hash_page(nip, phys, mode);
> > > }
> > >
> > > +/* When running on ppc64, we cannot use rfi anymore. Let's patch the
> > > vectors to use rfid instead.
> > > */
> > >
> > > +#define RFI     0x4c000064
> > > +#define RFID    0x4c000024
> > >
> > > +static void patch_rfi(char *from, uint32_t len)
> > > +{
> > > int i;
> > > for (i = 0; i < len; i += 4)  {
> > >    uint32_t* addr = (uint32_t *) (from + i);
> >
> > If you use a uint32* here you can just increment by 1 ...
>
> yes. I tried a couple of versions and that was the most friendly for the
> flush_icache_range.

Just call it for every instruction :)

Alex
> > >    if (*addr == RFI)
> > >        *addr = RFID;
> > > }
> > > flush_icache_range(from, from + len);
> > >
> > > +}
> > >
> > > +extern char __vectors[];
> > > +extern char __vectors_end[];
> >
> > And in fact you can just loop from vectors until ptr==vectors_end.
> >
> > uint32_t *ptr;
> >
> > for (ptr = __vectors; ptr != __vectors_end; ptr++)
> > > /************************************************************************/
> > > /*    init / cleanup                            */
> > > @@ -532,6 +552,10 @@ setup_mmu(unsigned long ramsize)
> > >
> > > memcpy((void *)get_rom_base(), (void *)OF_CODE_START, OF_CODE_SIZE);
> > > if (is_ppc64()) {
> > >    patch_rfi(0x0, (uint32_t) __vectors_end - (uint32_t) __vectors);
> > > }
> >
> > Just fold all of this together. Make patch_rfi have no parameters and just call it unconditionally. Then check for ppc64 in there.
>
> ok. v3 on the way.
>
> Thanks,
>
> C.
> > Alex
> > > /* Enable MMU */
> > >
> > > mtmsr(mfmsr() | MSR_IR | MSR_DR);

[Cédric Le Goater]

On 06/22/2016 06:50 AM, Alexander Graf wrote:
> > Am 21.06.2016 um 23:36 schrieb Cédric Le Goater :
> >
> > A recent attempt to restrict the use of rfi on 64bit cpus in qemu
> > broke 32bit OpenBIOS when run under a 970.
> >
> > This patches memory to replace rfi instructions with rfid in the
> > vector code.
> >
> > Signed-off-by: Cédric Le Goater 
> > Suggested-by: Alexander Graf
> >
> > Tested on qemu.
> >
> > arch/ppc/qemu/ofmem.c |   24 ++++++++++++++++++++++++
> > 1 file changed, 24 insertions(+)
> > Index: openbios.git/arch/ppc/qemu/ofmem.c
> >
> > --- openbios.git.orig/arch/ppc/qemu/ofmem.c
> > +++ openbios.git/arch/ppc/qemu/ofmem.c
> > @@ -478,6 +478,26 @@ isi_exception(void)
> >     hash_page(nip, phys, mode);
> > }
> >
> > +/* When running on ppc64, we cannot use rfi anymore. Let's patch the
> > vectors to use rfid instead.
> > */
> >
> > +#define RFI     0x4c000064
> > +#define RFID    0x4c000024
> >
> > +static void patch_rfi(char *from, uint32_t len)
> > +{
> > int i;
> > for (i = 0; i < len; i += 4)  {
> >    uint32_t* addr = (uint32_t *) (from + i);
>
> If you use a uint32* here you can just increment by 1 ...
> >    if (*addr == RFI)
> >        *addr = RFID;
> > }
> > flush_icache_range(from, from + len);
> >
> > +}
> >
> > +extern char __vectors[];
> > +extern char __vectors_end[];
>
> And in fact you can just loop from vectors until ptr==vectors_end.
>
> uint32_t *ptr;
>
> for (ptr = __vectors; ptr != __vectors_end; ptr++)

ah, we can not do that, we need to patch the memory and not the rom, so 
[ 0,  __vectors_end - __vectors]

C.
> > /************************************************************************/
> > /*    init / cleanup                            */
> > @@ -532,6 +552,10 @@ setup_mmu(unsigned long ramsize)
> > memcpy((void *)get_rom_base(), (void *)OF_CODE_START, OF_CODE_SIZE);
> >
> > if (is_ppc64()) {
> >    patch_rfi(0x0, (uint32_t) __vectors_end - (uint32_t) __vectors);
> > }
>
> Just fold all of this together. Make patch_rfi have no parameters and just call it unconditionally. Then check for ppc64 in there.
>
> Alex
> > /* Enable MMU */
> >
> > mtmsr(mfmsr() | MSR_IR | MSR_DR);

[Alexander Graf]

> Am 22.06.2016 um 09:08 schrieb Cédric Le Goater :
> > On 06/22/2016 06:50 AM, Alexander Graf wrote:
> > > Am 21.06.2016 um 23:36 schrieb Cédric Le Goater :
> > >
> > > A recent attempt to restrict the use of rfi on 64bit cpus in qemu
> > > broke 32bit OpenBIOS when run under a 970.
> > >
> > > This patches memory to replace rfi instructions with rfid in the
> > > vector code.
> > >
> > > Signed-off-by: Cédric Le Goater 
> > > Suggested-by: Alexander Graf
> > >
> > > Tested on qemu.
> > >
> > > arch/ppc/qemu/ofmem.c |   24 ++++++++++++++++++++++++
> > > 1 file changed, 24 insertions(+)
> > > Index: openbios.git/arch/ppc/qemu/ofmem.c
> > >
> > > --- openbios.git.orig/arch/ppc/qemu/ofmem.c
> > > +++ openbios.git/arch/ppc/qemu/ofmem.c
> > > @@ -478,6 +478,26 @@ isi_exception(void)
> > >    hash_page(nip, phys, mode);
> > > }
> > >
> > > +/* When running on ppc64, we cannot use rfi anymore. Let's patch the
> > > vectors to use rfid instead.
> > > */
> > >
> > > +#define RFI     0x4c000064
> > > +#define RFID    0x4c000024
> > >
> > > +static void patch_rfi(char *from, uint32_t len)
> > > +{
> > > int i;
> > > for (i = 0; i < len; i += 4)  {
> > >    uint32_t* addr = (uint32_t *) (from + i);
> >
> > If you use a uint32* here you can just increment by 1 ...
> > >    if (*addr == RFI)
> > >        *addr = RFID;
> > > }
> > > flush_icache_range(from, from + len);
> > >
> > > +}
> > >
> > > +extern char __vectors[];
> > > +extern char __vectors_end[];
> >
> > And in fact you can just loop from vectors until ptr==vectors_end.
> >
> > uint32_t *ptr;
> >
> > for (ptr = __vectors; ptr != __vectors_end; ptr++)
>
> ah, we can not do that, we need to patch the memory and not the rom, so 
> [ 0,  __vectors_end - __vectors]

Aaah, I see. Then your version makes more sense.
> C.
> > > /************************************************************************/
> > > /*    init / cleanup                            */
> > > @@ -532,6 +552,10 @@ setup_mmu(unsigned long ramsize)
> > >
> > > memcpy((void *)get_rom_base(), (void *)OF_CODE_START, OF_CODE_SIZE);
> > > if (is_ppc64()) {
> > >    patch_rfi(0x0, (uint32_t) __vectors_end - (uint32_t) __vectors);

Please cast to uintptr_t instead though :)

Alex
> > > }
> >
> > Just fold all of this together. Make patch_rfi have no parameters and just call it unconditionally. Then check for ppc64 in there.
> >
> > Alex
> > > /* Enable MMU */
> > >
> > > mtmsr(mfmsr() | MSR_IR | MSR_DR);