s390/alternatives: Rework to allow for callbacks

Rework alternatives to allow for callbacks. With this every
alternative entry has additional data encoded:

- When (aka context) an alternative is supposed to be applied

- The type of an alternative, which allows for type specific handling
  and callbacks

- Extra type specific payload (patch information), which can be passed
  to callbacks in order to decide if an alternative should be applied
  or not

With this only the "late" context is implemented, which means there is
no change to the previous behaviour. All code is just converted to the
more generic new infrastructure.

Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Tested-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

diff --git a/arch/s390/include/asm/alternative.h b/arch/s390/include/asm/alternative.h
index 16de33750d6c09ecfac332e32c4bb44f8e468d59..5b931070be16524f3bed763bb3de74334b858f84 100644 (file)
--- a/arch/s390/include/asm/alternative.h
+++ b/arch/s390/include/asm/alternative.h
@@ -2,6 +2,44 @@
 #ifndef _ASM_S390_ALTERNATIVE_H
 #define _ASM_S390_ALTERNATIVE_H
 
+/*
+ * Each alternative comes with a 32 bit feature field:
+ *     union {
+ *             u32 feature;
+ *             struct {
+ *                     u32 ctx  : 4;
+ *                     u32 type : 8;
+ *                     u32 data : 20;
+ *             };
+ *     }
+ *
+ * @ctx is a bitfield, where only one bit must be set. Each bit defines
+ * in which context an alternative is supposed to be applied to the
+ * kernel image:
+ *
+ * - from the decompressor before the kernel itself is executed
+ * - from early kernel code from within the kernel
+ *
+ * @type is a number which defines the type and with that the type
+ * specific alternative patching.
+ *
+ * @data is additional type specific information which defines if an
+ * alternative should be applied.
+ */
+
+#define ALT_CTX_LATE           1
+#define ALT_CTX_ALL            ALT_CTX_LATE
+
+#define ALT_TYPE_FACILITY      0
+
+#define ALT_DATA_SHIFT         0
+#define ALT_TYPE_SHIFT         20
+#define ALT_CTX_SHIFT          28
+
+#define ALT_FACILITY(facility)         (ALT_CTX_LATE << ALT_CTX_SHIFT          | \
+                                        ALT_TYPE_FACILITY << ALT_TYPE_SHIFT    | \
+                                        (facility) << ALT_DATA_SHIFT)
+
 #ifndef __ASSEMBLY__
 
 #include <linux/types.h>
@@ -11,12 +49,30 @@
 struct alt_instr {
        s32 instr_offset;       /* original instruction */
        s32 repl_offset;        /* offset to replacement instruction */
-       u16 feature;            /* feature required for replacement */
+       union {
+               u32 feature;    /* feature required for replacement */
+               struct {
+                       u32 ctx  : 4;  /* context */
+                       u32 type : 8;  /* type of alternative */
+                       u32 data : 20; /* patching information */
+               };
+       };
        u8  instrlen;           /* length of original instruction */
 } __packed;
 
-void apply_alternative_instructions(void);
-void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
+extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
+
+void __apply_alternatives(struct alt_instr *start, struct alt_instr *end, unsigned int ctx);
+
+static inline void apply_alternative_instructions(void)
+{
+       __apply_alternatives(__alt_instructions, __alt_instructions_end, ALT_CTX_LATE);
+}
+
+static inline void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
+{
+       __apply_alternatives(start, end, ALT_CTX_ALL);
+}
 
 /*
  * +---------------------------------+
@@ -51,7 +107,7 @@ void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
 #define ALTINSTR_ENTRY(feature, num)                                   \
        "\t.long 661b - .\n"                    /* old instruction */   \
        "\t.long " b_altinstr(num)"b - .\n"     /* alt instruction */   \
-       "\t.word " __stringify(feature) "\n"    /* feature         */   \
+       "\t.long " __stringify(feature) "\n"    /* feature         */   \
        "\t.byte " oldinstr_len "\n"            /* instruction len */   \
        "\t.org . - (" oldinstr_len ") & 1\n"                           \
        "\t.org . - (" oldinstr_len ") + (" altinstr_len(num) ")\n"     \
@@ -127,7 +183,7 @@ void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
 .macro alt_entry orig_start, orig_end, alt_start, alt_end, feature
        .long   \orig_start - .
        .long   \alt_start - .
-       .word   \feature
+       .long   \feature
        .byte   \orig_end - \orig_start
        .org    . - ( \orig_end - \orig_start ) & 1
        .org    . - ( \orig_end - \orig_start ) + ( \alt_end - \alt_start )

diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index 5debb12614adbbe7fc54000f302c821d2b7fe764..8a52554f49f09732446f758e5f7d27bc992656b5 100644 (file)
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -419,7 +419,7 @@ static __always_inline bool regs_irqs_disabled(struct pt_regs *regs)
 
 static __always_inline void bpon(void)
 {
-       asm volatile(ALTERNATIVE("nop", ".insn  rrf,0xb2e80000,0,0,13,0", 82));
+       asm volatile(ALTERNATIVE("nop", ".insn  rrf,0xb2e80000,0,0,13,0", ALT_FACILITY(82)));
 }
 
 #endif /* __ASSEMBLY__ */

diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
index 3e43c90ff1354612de111ef55cc22e930e0c12e9..77d5e804af93e5a2ed2412f20a8f5a6b72ed65e5 100644 (file)
--- a/arch/s390/include/asm/spinlock.h
+++ b/arch/s390/include/asm/spinlock.h
@@ -79,7 +79,7 @@ static inline void arch_spin_unlock(arch_spinlock_t *lp)
        typecheck(int, lp->lock);
        kcsan_release();
        asm_inline volatile(
-               ALTERNATIVE("nop", ".insn rre,0xb2fa0000,7,0", 49) /* NIAI 7 */
+               ALTERNATIVE("nop", ".insn rre,0xb2fa0000,7,0", ALT_FACILITY(49)) /* NIAI 7 */
                "       sth     %1,%0\n"
                : "=R" (((unsigned short *) &lp->lock)[1])
                : "d" (0) : "cc", "memory");

diff --git a/arch/s390/kernel/alternative.c b/arch/s390/kernel/alternative.c
index 33debc2a26c919436240c9758787c41c515157ce..ecabdff89bce0bea59e1ea279ae776bb00003fdc 100644 (file)
--- a/arch/s390/kernel/alternative.c
+++ b/arch/s390/kernel/alternative.c
@@ -1,31 +1,33 @@
 // SPDX-License-Identifier: GPL-2.0
-#include <linux/module.h>
+
+#include <linux/uaccess.h>
 #include <asm/alternative.h>
 #include <asm/facility.h>
-#include <asm/nospec-branch.h>
 
-void __init_or_module apply_alternatives(struct alt_instr *start,
-                                        struct alt_instr *end)
+void __apply_alternatives(struct alt_instr *start, struct alt_instr *end, unsigned int ctx)
 {
-       struct alt_instr *a;
        u8 *instr, *replacement;
+       struct alt_instr *a;
+       bool replace;
 
        /*
         * The scan order should be from start to end. A later scanned
         * alternative code can overwrite previously scanned alternative code.
         */
        for (a = start; a < end; a++) {
+               if (!(a->ctx & ctx))
+                       continue;
+               switch (a->type) {
+               case ALT_TYPE_FACILITY:
+                       replace = __test_facility(a->data, alt_stfle_fac_list);
+                       break;
+               default:
+                       replace = false;
+               }
+               if (!replace)
+                       continue;
                instr = (u8 *)&a->instr_offset + a->instr_offset;
                replacement = (u8 *)&a->repl_offset + a->repl_offset;
-
-               if (!__test_facility(a->feature, alt_stfle_fac_list))
-                       continue;
                s390_kernel_write(instr, replacement, a->instrlen);
        }
 }
-
-extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
-void __init apply_alternative_instructions(void)
-{
-       apply_alternatives(__alt_instructions, __alt_instructions_end);
-}

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 866917ff013fae051c3a5d166d4c22a89554623a..90027a57a524900eb0a9f454016ee0a12206f9bb 100644 (file)
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -32,19 +32,19 @@
 _LPP_OFFSET    = __LC_LPP
 
        .macro STBEAR address
-       ALTERNATIVE "nop", ".insn s,0xb2010000,\address", 193
+       ALTERNATIVE "nop", ".insn s,0xb2010000,\address", ALT_FACILITY(193)
        .endm
 
        .macro LBEAR address
-       ALTERNATIVE "nop", ".insn s,0xb2000000,\address", 193
+       ALTERNATIVE "nop", ".insn s,0xb2000000,\address", ALT_FACILITY(193)
        .endm
 
        .macro LPSWEY address,lpswe
-       ALTERNATIVE "b \lpswe; nopr", ".insn siy,0xeb0000000071,\address,0", 193
+       ALTERNATIVE "b \lpswe; nopr", ".insn siy,0xeb0000000071,\address,0", ALT_FACILITY(193)
        .endm
 
        .macro MBEAR reg
-       ALTERNATIVE "brcl 0,0", __stringify(mvc __PT_LAST_BREAK(8,\reg),__LC_LAST_BREAK), 193
+       ALTERNATIVE "brcl 0,0", __stringify(mvc __PT_LAST_BREAK(8,\reg),__LC_LAST_BREAK), ALT_FACILITY(193)
        .endm
 
        .macro  CHECK_STACK savearea
@@ -100,22 +100,22 @@ _LPP_OFFSET       = __LC_LPP
        .endm
 
        .macro BPOFF
-       ALTERNATIVE "nop", ".insn rrf,0xb2e80000,0,0,12,0", 82
+       ALTERNATIVE "nop", ".insn rrf,0xb2e80000,0,0,12,0", ALT_FACILITY(82)
        .endm
 
        .macro BPON
-       ALTERNATIVE "nop", ".insn rrf,0xb2e80000,0,0,13,0", 82
+       ALTERNATIVE "nop", ".insn rrf,0xb2e80000,0,0,13,0", ALT_FACILITY(82)
        .endm
 
        .macro BPENTER tif_ptr,tif_mask
        ALTERNATIVE "TSTMSK \tif_ptr,\tif_mask; jz .+8; .insn rrf,0xb2e80000,0,0,13,0", \
-                   "j .+12; nop; nop", 82
+                   "j .+12; nop; nop", ALT_FACILITY(82)
        .endm
 
        .macro BPEXIT tif_ptr,tif_mask
        TSTMSK  \tif_ptr,\tif_mask
        ALTERNATIVE "jz .+8;  .insn rrf,0xb2e80000,0,0,12,0", \
-                   "jnz .+8; .insn rrf,0xb2e80000,0,0,13,0", 82
+                   "jnz .+8; .insn rrf,0xb2e80000,0,0,13,0", ALT_FACILITY(82)
        .endm
 
 #if IS_ENABLED(CONFIG_KVM)
@@ -169,7 +169,7 @@ SYM_FUNC_START(__switch_to_asm)
        aghi    %r3,__TASK_pid
        mvc     __LC_CURRENT_PID(4,%r0),0(%r3)  # store pid of next
        lmg     %r6,%r15,__SF_GPRS(%r15)        # load gprs of next task
-       ALTERNATIVE "nop", "lpp _LPP_OFFSET", 40
+       ALTERNATIVE "nop", "lpp _LPP_OFFSET", ALT_FACILITY(40)
        BR_EX   %r14
 SYM_FUNC_END(__switch_to_asm)
 
@@ -515,7 +515,7 @@ SYM_CODE_START(mcck_int_handler)
        jno     0f
        BPON
        stpt    __LC_EXIT_TIMER
-0:     ALTERNATIVE "nop", __stringify(lghi %r12,__LC_LAST_BREAK_SAVE_AREA),193
+0:     ALTERNATIVE "nop", __stringify(lghi %r12,__LC_LAST_BREAK_SAVE_AREA), ALT_FACILITY(193)
        LBEAR   0(%r12)
        lmg     %r11,%r15,__PT_R11(%r11)
        LPSWEY  __LC_RETURN_MCCK_PSW,__LC_RETURN_MCCK_LPSWE
@@ -551,7 +551,7 @@ SYM_CODE_START(mcck_int_handler)
 SYM_CODE_END(mcck_int_handler)
 
 SYM_CODE_START(restart_int_handler)
-       ALTERNATIVE "nop", "lpp _LPP_OFFSET", 40
+       ALTERNATIVE "nop", "lpp _LPP_OFFSET", ALT_FACILITY(40)
        stg     %r15,__LC_SAVE_AREA_RESTART
        TSTMSK  __LC_RESTART_FLAGS,RESTART_FLAG_CTLREGS,4
        jz      0f

diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
index 0c9a73a18826ca7ecb7cc13851f3cbe9b69dfe59..9f86ad8fa8b4dca716de58d4fe0313cdc4818f31 100644 (file)
--- a/arch/s390/lib/spinlock.c
+++ b/arch/s390/lib/spinlock.c
@@ -75,7 +75,7 @@ static inline int arch_load_niai4(int *lock)
        int owner;
 
        asm_inline volatile(
-               ALTERNATIVE("nop", ".insn rre,0xb2fa0000,4,0", 49) /* NIAI 4 */
+               ALTERNATIVE("nop", ".insn rre,0xb2fa0000,4,0", ALT_FACILITY(49)) /* NIAI 4 */
                "       l       %0,%1\n"
                : "=d" (owner) : "Q" (*lock) : "memory");
        return owner;
@@ -86,7 +86,7 @@ static inline int arch_cmpxchg_niai8(int *lock, int old, int new)
        int expected = old;
 
        asm_inline volatile(
-               ALTERNATIVE("nop", ".insn rre,0xb2fa0000,8,0", 49) /* NIAI 8 */
+               ALTERNATIVE("nop", ".insn rre,0xb2fa0000,8,0", ALT_FACILITY(49)) /* NIAI 8 */
                "       cs      %0,%3,%1\n"
                : "=d" (old), "=Q" (*lock)
                : "0" (old), "d" (new), "Q" (*lock)