sh: boot kernel with SR.BL set

Update the SH kernel to keep SR.BL set until the VBR
register has been initialized. Useful to allow boot
of the kernel even though exceptions are pending.

Without this patch there is a window of time when
exceptions such as NMI are enabled but no exception
handlers are installed.

This patch modifies both the zImage loader and the
actual kernel to boot with BL=1, but the zImage
loader is modfied in such a way that the init_sr
value is unchanged to not break the zImage loader
provided by kexec.

Tested on sh7724 Ecovec and on the SH4AL-DSP core
included in sh7372.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

diff --git a/arch/sh/boot/compressed/head_32.S b/arch/sh/boot/compressed/head_32.S
index 200c1d4f1efe4c518a6470993603d748550d4eae..3e150326f1fd8a16a6161d6ce796c5ba63094c15 100644 (file)
--- a/arch/sh/boot/compressed/head_32.S
+++ b/arch/sh/boot/compressed/head_32.S
@@ -91,7 +91,9 @@ bss_start_addr:
 end_addr:
        .long   _end
 init_sr:
-       .long   0x400000F0      /* Privileged mode, Bank=0, Block=0, IMASK=0xF */
+       .long   0x500000F0      /* Privileged mode, Bank=0, Block=1, IMASK=0xF */
+kexec_magic:
+       .long   0x400000F0      /* magic used by kexec to parse zImage format */
 init_stack_addr:
        .long   stack_start
 decompress_kernel_addr:

diff --git a/arch/sh/kernel/head_32.S b/arch/sh/kernel/head_32.S
index 6e35f012cc0361150804c9f6084ac176c0ba75f0..7db248936b60ef7ca6639fc3420612b0c22d06d3 100644 (file)
--- a/arch/sh/kernel/head_32.S
+++ b/arch/sh/kernel/head_32.S
@@ -330,7 +330,7 @@ ENTRY(_stext)
 #if defined(CONFIG_CPU_SH2)
 1:     .long   0x000000F0              ! IMASK=0xF
 #else
-1:     .long   0x400080F0              ! MD=1, RB=0, BL=0, FD=1, IMASK=0xF
+1:     .long   0x500080F0              ! MD=1, RB=0, BL=1, FD=1, IMASK=0xF
 #endif
 ENTRY(stack_start)
 2:     .long   init_thread_union+THREAD_SIZE

diff --git a/arch/sh/kernel/traps_32.c b/arch/sh/kernel/traps_32.c
index c3d86fa71ddfc9bbe2b98819fe9a2513becb5e8e..f5613529a6bfe174a7dc4e27fcd67ece9d9949ab 100644 (file)
--- a/arch/sh/kernel/traps_32.c
+++ b/arch/sh/kernel/traps_32.c
@@ -802,6 +802,9 @@ void __cpuinit per_cpu_trap_init(void)
                     : /* no output */
                     : "r" (&vbr_base)
                     : "memory");
+
+       /* disable exception blocking now when the vbr has been setup */
+       clear_bl_bit();
 }
 
 void *set_exception_table_vec(unsigned int vec, void *handler)