The CPU15 erratum on MPC8xx chips can cause incorrect code execution
under certain circumstances, where there is a conditional or indirect
branch in the last word of a page, with a target in the last cache line
of the next page. This patch implements one of the suggested
workarounds, by forcing a TLB miss whenever execution crosses a page
boundary. This is done by invalidating the pages before and after the
one being loaded into the TLB in the ITLB miss handler.
Signed-off-by: Scott Wood <[EMAIL PROTECTED]>
---
arch/powerpc/kernel/head_8xx.S | 6 ++++++
arch/powerpc/platforms/8xx/Kconfig | 16 ++++++++++++++++
2 files changed, 22 insertions(+), 0 deletions(-)
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index e40e122..dd223df 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -301,6 +301,12 @@ InstructionTLBMiss:
stw r10, 0(r0)
stw r11, 4(r0)
mfspr r10, SPRN_SRR0 /* Get effective address of fault */
+#ifdef CONFIG_8xx_CPU15
+ addi r11, r10, 0x1000
+ tlbie r11
+ addi r11, r10, -0x1000
+ tlbie r11
+#endif
DO_8xx_CPU6(0x3780, r3)
mtspr SPRN_MD_EPN, r10 /* Have to use MD_EPN for walk, MI_EPN
can't */
mfspr r10, SPRN_M_TWB /* Get level 1 table entry address */
diff --git a/arch/powerpc/platforms/8xx/Kconfig
b/arch/powerpc/platforms/8xx/Kconfig
index 8ecd01a..322b155 100644
--- a/arch/powerpc/platforms/8xx/Kconfig
+++ b/arch/powerpc/platforms/8xx/Kconfig
@@ -100,6 +100,22 @@ config 8xx_CPU6
If in doubt, say N here.
+config 8xx_CPU15
+ bool "CPU15 Silicon Errata"
+ default y
+ help
+ This enables a workaround for erratum CPU15 on MPC8xx chips.
+ This bug can cause incorrect code execution under certain
+ circumstances. This workaround adds some overhead (a TLB miss
+ every time execution crosses a page boundary), and you may wish
+ to disable it if you have worked around the bug in the compiler
+ (by not placing conditional branches or branches to LR or CTR
+ in the last word of a page, with a target of the last cache
+ line in the next page), or if you have used some other
+ workaround.
+
+ If in doubt, say Y here.
+
choice
prompt "Microcode patch selection"
default NO_UCODE_PATCH
--
1.5.3
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