powerpc/64s: fix scv entry fallback flush vs interrupt

commit 08685be7761d69914f08c3d6211c543a385a5b9c upstream.

The L1D flush fallback functions are not recoverable vs interrupts,
yet the scv entry flush runs with MSR[EE]=1. This can result in a
timer (soft-NMI) or MCE or SRESET interrupt hitting here and overwriting
the EXRFI save area, which ends up corrupting userspace registers for
scv return.

Fix this by disabling RI and EE for the scv entry fallback flush.

Fixes: f79643787e0a0 ("powerpc/64s: flush L1D on kernel entry")
Cc: stable@vger.kernel.org # 5.9+ which also have flush L1D patch backport
Reported-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210111062408.287092-1-npiggin@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 1d32b17..c1a8aac 100644 (file)
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -63,6 +63,12 @@
        nop;                                                            \
        nop;
 
+#define SCV_ENTRY_FLUSH_SLOT                                           \
+       SCV_ENTRY_FLUSH_FIXUP_SECTION;                                  \
+       nop;                                                            \
+       nop;                                                            \
+       nop;
+
 /*
  * r10 must be free to use, r13 must be paca
  */
@@ -71,6 +77,13 @@
        ENTRY_FLUSH_SLOT
 
 /*
+ * r10, ctr must be free to use, r13 must be paca
+ */
+#define SCV_INTERRUPT_TO_KERNEL                                                \
+       STF_ENTRY_BARRIER_SLOT;                                         \
+       SCV_ENTRY_FLUSH_SLOT
+
+/*
  * Macros for annotating the expected destination of (h)rfid
  *
  * The nop instructions allow us to insert one or more instructions to flush the

diff --git a/arch/powerpc/include/asm/feature-fixups.h b/arch/powerpc/include/asm/feature-fixups.h
index fbd406c..8d10005 100644 (file)
--- a/arch/powerpc/include/asm/feature-fixups.h
+++ b/arch/powerpc/include/asm/feature-fixups.h
@@ -221,6 +221,14 @@ label##3:                                          \
        FTR_ENTRY_OFFSET 957b-958b;                     \
        .popsection;
 
+#define SCV_ENTRY_FLUSH_FIXUP_SECTION                  \
+957:                                                   \
+       .pushsection __scv_entry_flush_fixup,"a";       \
+       .align 2;                                       \
+958:                                                   \
+       FTR_ENTRY_OFFSET 957b-958b;                     \
+       .popsection;
+
 #define RFI_FLUSH_FIXUP_SECTION                                \
 951:                                                   \
        .pushsection __rfi_flush_fixup,"a";             \
@@ -254,10 +262,12 @@ label##3:                                         \
 
 extern long stf_barrier_fallback;
 extern long entry_flush_fallback;
+extern long scv_entry_flush_fallback;
 extern long __start___stf_entry_barrier_fixup, __stop___stf_entry_barrier_fixup;
 extern long __start___stf_exit_barrier_fixup, __stop___stf_exit_barrier_fixup;
 extern long __start___uaccess_flush_fixup, __stop___uaccess_flush_fixup;
 extern long __start___entry_flush_fixup, __stop___entry_flush_fixup;
+extern long __start___scv_entry_flush_fixup, __stop___scv_entry_flush_fixup;
 extern long __start___rfi_flush_fixup, __stop___rfi_flush_fixup;
 extern long __start___barrier_nospec_fixup, __stop___barrier_nospec_fixup;
 extern long __start__btb_flush_fixup, __stop__btb_flush_fixup;

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 2f38461..2831b0a 100644 (file)
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -75,7 +75,7 @@ BEGIN_FTR_SECTION
        bne     .Ltabort_syscall
 END_FTR_SECTION_IFSET(CPU_FTR_TM)
 #endif
-       INTERRUPT_TO_KERNEL
+       SCV_INTERRUPT_TO_KERNEL
        mr      r10,r1
        ld      r1,PACAKSAVE(r13)
        std     r10,0(r1)

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 4d01f09..3cde2fb 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -2993,6 +2993,25 @@ TRAMP_REAL_BEGIN(entry_flush_fallback)
        ld      r11,PACA_EXRFI+EX_R11(r13)
        blr
 
+/*
+ * The SCV entry flush happens with interrupts enabled, so it must disable
+ * to prevent EXRFI being clobbered by NMIs (e.g., soft_nmi_common). r10
+ * (containing LR) does not need to be preserved here because scv entry
+ * puts 0 in the pt_regs, CTR can be clobbered for the same reason.
+ */
+TRAMP_REAL_BEGIN(scv_entry_flush_fallback)
+       li      r10,0
+       mtmsrd  r10,1
+       lbz     r10,PACAIRQHAPPENED(r13)
+       ori     r10,r10,PACA_IRQ_HARD_DIS
+       stb     r10,PACAIRQHAPPENED(r13)
+       std     r11,PACA_EXRFI+EX_R11(r13)
+       L1D_DISPLACEMENT_FLUSH
+       ld      r11,PACA_EXRFI+EX_R11(r13)
+       li      r10,MSR_RI
+       mtmsrd  r10,1
+       blr
+
 TRAMP_REAL_BEGIN(rfi_flush_fallback)
        SET_SCRATCH0(r13);
        GET_PACA(r13);

diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 83281ae..4a1f494 100644 (file)
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -146,6 +146,13 @@ SECTIONS
        }
 
        . = ALIGN(8);
+       __scv_entry_flush_fixup : AT(ADDR(__scv_entry_flush_fixup) - LOAD_OFFSET) {
+               __start___scv_entry_flush_fixup = .;
+               *(__scv_entry_flush_fixup)
+               __stop___scv_entry_flush_fixup = .;
+       }
+
+       . = ALIGN(8);
        __stf_exit_barrier_fixup : AT(ADDR(__stf_exit_barrier_fixup) - LOAD_OFFSET) {
                __start___stf_exit_barrier_fixup = .;
                *(__stf_exit_barrier_fixup)

diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-fixups.c
index 321c12a..92705d6 100644 (file)
--- a/arch/powerpc/lib/feature-fixups.c
+++ b/arch/powerpc/lib/feature-fixups.c
@@ -290,9 +290,6 @@ void do_entry_flush_fixups(enum l1d_flush_type types)
        long *start, *end;
        int i;
 
-       start = PTRRELOC(&__start___entry_flush_fixup);
-       end = PTRRELOC(&__stop___entry_flush_fixup);
-
        instrs[0] = 0x60000000; /* nop */
        instrs[1] = 0x60000000; /* nop */
        instrs[2] = 0x60000000; /* nop */
@@ -312,6 +309,8 @@ void do_entry_flush_fixups(enum l1d_flush_type types)
        if (types & L1D_FLUSH_MTTRIG)
                instrs[i++] = 0x7c12dba6; /* mtspr TRIG2,r0 (SPR #882) */
 
+       start = PTRRELOC(&__start___entry_flush_fixup);
+       end = PTRRELOC(&__stop___entry_flush_fixup);
        for (i = 0; start < end; start++, i++) {
                dest = (void *)start + *start;
 
@@ -328,6 +327,25 @@ void do_entry_flush_fixups(enum l1d_flush_type types)
                patch_instruction((struct ppc_inst *)(dest + 2), ppc_inst(instrs[2]));
        }
 
+       start = PTRRELOC(&__start___scv_entry_flush_fixup);
+       end = PTRRELOC(&__stop___scv_entry_flush_fixup);
+       for (; start < end; start++, i++) {
+               dest = (void *)start + *start;
+
+               pr_devel("patching dest %lx\n", (unsigned long)dest);
+
+               patch_instruction((struct ppc_inst *)dest, ppc_inst(instrs[0]));
+
+               if (types == L1D_FLUSH_FALLBACK)
+                       patch_branch((struct ppc_inst *)(dest + 1), (unsigned long)&scv_entry_flush_fallback,
+                                    BRANCH_SET_LINK);
+               else
+                       patch_instruction((struct ppc_inst *)(dest + 1), ppc_inst(instrs[1]));
+
+               patch_instruction((struct ppc_inst *)(dest + 2), ppc_inst(instrs[2]));
+       }
+
+
        printk(KERN_DEBUG "entry-flush: patched %d locations (%s flush)\n", i,
                (types == L1D_FLUSH_NONE)       ? "no" :
                (types == L1D_FLUSH_FALLBACK)   ? "fallback displacement" :