Since commit b86fb88855ea ("powerpc/32: implement fast entry for syscalls on non BOOKE") and commit 1a4b739bbb4f ("powerpc/32: implement fast entry for syscalls on BOOKE"), syscalls from kernel are unexpected and can have catastrophic consequences as it will destroy the kernel stack.
Test MSR_PR on syscall entry. In case syscall is from kernel, emit a warning and return ENOSYS error. Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr> --- v2: Rebased on powerpc/next-test, ie on top of VMAP_STACK series v3: - Rebased on today's powerpc/merge. - Reloading both SRR0 and SRR1 in ret_from_kernel_syscall allthough SRR1 is already in r9 at the time being, allows more flexibility and less prone to risk of errors for future changes in the syscall entry. Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr> --- arch/powerpc/kernel/entry_32.S | 27 +++++++++++++++++++++++++++ arch/powerpc/kernel/head_32.h | 16 +++++++++------- arch/powerpc/kernel/head_booke.h | 5 ++++- 3 files changed, 40 insertions(+), 8 deletions(-) diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S index 77abbc34bbe0..e808626ff230 100644 --- a/arch/powerpc/kernel/entry_32.S +++ b/arch/powerpc/kernel/entry_32.S @@ -575,6 +575,33 @@ syscall_exit_work: bl do_syscall_trace_leave b ret_from_except_full + /* + * System call was called from kernel. We get here with SRR1 in r9. + * Mark the exception as recoverable once we have retrieved SRR0, + * trap a warning and return ENOSYS with CR[SO] set. + */ + .globl ret_from_kernel_syscall +ret_from_kernel_syscall: + mfspr r9, SPRN_SRR0 + mfspr r10, SPRN_SRR1 +#if !defined(CONFIG_4xx) && !defined(CONFIG_BOOKE) + LOAD_REG_IMMEDIATE(r11, MSR_KERNEL & ~(MSR_IR|MSR_DR)) + mtmsr r11 +#endif + +0: trap + EMIT_BUG_ENTRY 0b,__FILE__,__LINE__, BUGFLAG_WARNING + + li r3, ENOSYS + crset so +#if defined(CONFIG_PPC_8xx) && defined(CONFIG_PERF_EVENTS) + mtspr SPRN_NRI, r0 +#endif + mtspr SPRN_SRR0, r9 + mtspr SPRN_SRR1, r10 + SYNC + RFI + /* * The fork/clone functions need to copy the full register set into * the child process. Therefore we need to save all the nonvolatile diff --git a/arch/powerpc/kernel/head_32.h b/arch/powerpc/kernel/head_32.h index a6a5fbbf8504..0e7bf28fe53a 100644 --- a/arch/powerpc/kernel/head_32.h +++ b/arch/powerpc/kernel/head_32.h @@ -111,14 +111,16 @@ .macro SYSCALL_ENTRY trapno mfspr r12,SPRN_SPRG_THREAD + mfspr r9, SPRN_SRR1 #ifdef CONFIG_VMAP_STACK - mfspr r9, SPRN_SRR0 - mfspr r11, SPRN_SRR1 - stw r9, SRR0(r12) - stw r11, SRR1(r12) + mfspr r11, SPRN_SRR0 + stw r11, SRR0(r12) + stw r9, SRR1(r12) #endif mfcr r10 + andi. r11, r9, MSR_PR lwz r11,TASK_STACK-THREAD(r12) + beq- 99f rlwinm r10,r10,0,4,2 /* Clear SO bit in CR */ addi r11, r11, THREAD_SIZE - INT_FRAME_SIZE #ifdef CONFIG_VMAP_STACK @@ -128,15 +130,14 @@ #endif tovirt_vmstack r12, r12 tophys_novmstack r11, r11 - mflr r9 stw r10,_CCR(r11) /* save registers */ - stw r9, _LINK(r11) + mflr r10 + stw r10, _LINK(r11) #ifdef CONFIG_VMAP_STACK lwz r10, SRR0(r12) lwz r9, SRR1(r12) #else mfspr r10,SPRN_SRR0 - mfspr r9,SPRN_SRR1 #endif stw r1,GPR1(r11) stw r1,0(r11) @@ -209,6 +210,7 @@ mtspr SPRN_SRR0,r11 SYNC RFI /* jump to handler, enable MMU */ +99: b ret_from_kernel_syscall .endm .macro save_dar_dsisr_on_stack reg1, reg2, sp diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h index 37fc84ed90e3..bd2e5ed8dd50 100644 --- a/arch/powerpc/kernel/head_booke.h +++ b/arch/powerpc/kernel/head_booke.h @@ -104,16 +104,18 @@ FTR_SECTION_ELSE #ifdef CONFIG_KVM_BOOKE_HV ALT_FTR_SECTION_END_IFSET(CPU_FTR_EMB_HV) #endif + mfspr r9, SPRN_SRR1 BOOKE_CLEAR_BTB(r11) + andi. r11, r9, MSR_PR lwz r11, TASK_STACK - THREAD(r10) rlwinm r12,r12,0,4,2 /* Clear SO bit in CR */ + beq- 99f ALLOC_STACK_FRAME(r11, THREAD_SIZE - INT_FRAME_SIZE) stw r12, _CCR(r11) /* save various registers */ mflr r12 stw r12,_LINK(r11) mfspr r12,SPRN_SRR0 stw r1, GPR1(r11) - mfspr r9,SPRN_SRR1 stw r1, 0(r11) mr r1, r11 stw r12,_NIP(r11) @@ -176,6 +178,7 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_EMB_HV) mtspr SPRN_SRR0,r11 SYNC RFI /* jump to handler, enable MMU */ +99: b ret_from_kernel_syscall .endm /* To handle the additional exception priority levels on 40x and Book-E -- 2.25.0