As spotted and explained in commit c12ab8dbc492 ("powerpc/8xx: Fix Oops with STRICT_KERNEL_RWX without DEBUG_RODATA_TEST"), the selection of STRICT_KERNEL_RWX without selecting DEBUG_RODATA_TEST has spotted the lack of the DIRTY bit in the pinned kernel data TLBs.
This problem should have been detected a lot earlier if things had been working as expected. But due to an incredible level of chance or mishap, this went undetected because of a set of bugs: In fact the DTLBs were not pinned, because instead of setting the reserve bit in MD_CTR, it was set in MI_CTR that is the register for ITLBs.
But then, another huge bug was there: the physical address was reset to 0 at the boundary between RO and RW areas, leading to the same physical space being mapped at both 0xc0000000 and 0xc8000000. This had by miracle no consequence until now because the entry was not really pinned so it was overwritten soon enough to go undetected.
Of course, now that we really pin the DTLBs, it must be fixed as well.
Depends-on: c12ab8dbc492 ("powerpc/8xx: Fix Oops with STRICT_KERNEL_RWX without DEBUG_RODATA_TEST") Fixes: f76c8f6d257c ("powerpc/8xx: Add function to set pinned TLBs") Cc: stable@vger.kernel.org Signed-off-by: Christophe Leroy christophe.leroy@csgroup.eu --- arch/powerpc/kernel/head_8xx.S | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S index 2d596881b70e..0d073b9fd52c 100644 --- a/arch/powerpc/kernel/head_8xx.S +++ b/arch/powerpc/kernel/head_8xx.S @@ -733,6 +733,7 @@ _GLOBAL(mmu_pin_tlb) #ifdef CONFIG_PIN_TLB_DATA LOAD_REG_IMMEDIATE(r6, PAGE_OFFSET) LOAD_REG_IMMEDIATE(r7, MI_SVALID | MI_PS8MEG | _PMD_ACCESSED) + li r8, 0 #ifdef CONFIG_PIN_TLB_IMMR li r0, 3 #else @@ -741,26 +742,26 @@ _GLOBAL(mmu_pin_tlb) mtctr r0 cmpwi r4, 0 beq 4f - LOAD_REG_IMMEDIATE(r8, 0xf0 | _PAGE_RO | _PAGE_SPS | _PAGE_SH | _PAGE_PRESENT) LOAD_REG_ADDR(r9, _sinittext)
2: ori r0, r6, MD_EVALID + ori r12, r8, 0xf0 | _PAGE_RO | _PAGE_SPS | _PAGE_SH | _PAGE_PRESENT mtspr SPRN_MD_CTR, r5 mtspr SPRN_MD_EPN, r0 mtspr SPRN_MD_TWC, r7 - mtspr SPRN_MD_RPN, r8 + mtspr SPRN_MD_RPN, r12 addi r5, r5, 0x100 addis r6, r6, SZ_8M@h addis r8, r8, SZ_8M@h cmplw r6, r9 bdnzt lt, 2b - -4: LOAD_REG_IMMEDIATE(r8, 0xf0 | _PAGE_DIRTY | _PAGE_SPS | _PAGE_SH | _PAGE_PRESENT) +4: 2: ori r0, r6, MD_EVALID + ori r12, r8, 0xf0 | _PAGE_DIRTY | _PAGE_SPS | _PAGE_SH | _PAGE_PRESENT mtspr SPRN_MD_CTR, r5 mtspr SPRN_MD_EPN, r0 mtspr SPRN_MD_TWC, r7 - mtspr SPRN_MD_RPN, r8 + mtspr SPRN_MD_RPN, r12 addi r5, r5, 0x100 addis r6, r6, SZ_8M@h addis r8, r8, SZ_8M@h @@ -781,7 +782,7 @@ _GLOBAL(mmu_pin_tlb) #endif #if defined(CONFIG_PIN_TLB_IMMR) || defined(CONFIG_PIN_TLB_DATA) lis r0, (MD_RSV4I | MD_TWAM)@h - mtspr SPRN_MI_CTR, r0 + mtspr SPRN_MD_CTR, r0 #endif mtspr SPRN_SRR1, r10 mtspr SPRN_SRR0, r11