powerpc/64: use 32-bit immediate for STACK_FRAME_REGS_MARKER

Using a 32-bit constant for this marker allows it to be loaded with
two ALU instructions, like 32-bit. This avoids a TOC entry and a
TOC load that depends on the r2 value that has just been loaded from
the PACA.

This changes the value for 32-bit as well, so both have the same
value in the low 4 bytes and 64-bit has 0 in the top bytes.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220926034057.2360083-2-npiggin@gmail.com

diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h
index a034036..5b496e5 100644 (file)
--- a/arch/powerpc/include/asm/ptrace.h
+++ b/arch/powerpc/include/asm/ptrace.h
@@ -99,6 +99,8 @@ struct pt_regs
 
 #define STACK_FRAME_WITH_PT_REGS (STACK_FRAME_OVERHEAD + sizeof(struct pt_regs))
 
+#define STACK_FRAME_REGS_MARKER        ASM_CONST(0x72656773)
+
 #ifdef __powerpc64__
 
 /*
@@ -115,7 +117,6 @@ struct pt_regs
 
 #define STACK_FRAME_OVERHEAD   112     /* size of minimum stack frame */
 #define STACK_FRAME_LR_SAVE    2       /* Location of LR in stack frame */
-#define STACK_FRAME_REGS_MARKER        ASM_CONST(0x7265677368657265)
 #define STACK_INT_FRAME_SIZE   (sizeof(struct pt_regs) + \
                                 STACK_FRAME_OVERHEAD + KERNEL_REDZONE_SIZE)
 #define STACK_FRAME_MARKER     12
@@ -136,7 +137,6 @@ struct pt_regs
 #define KERNEL_REDZONE_SIZE    0
 #define STACK_FRAME_OVERHEAD   16      /* size of minimum stack frame */
 #define STACK_FRAME_LR_SAVE    1       /* Location of LR in stack frame */
-#define STACK_FRAME_REGS_MARKER        ASM_CONST(0x72656773)
 #define STACK_INT_FRAME_SIZE   (sizeof(struct pt_regs) + STACK_FRAME_OVERHEAD)
 #define STACK_FRAME_MARKER     2
 #define STACK_FRAME_MIN_SIZE   STACK_FRAME_OVERHEAD

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 55fcc70..3fc7c98 100644 (file)
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -263,7 +263,7 @@ fast_exception_return:
        mtcr    r10
        lwz     r10,_LINK(r11)
        mtlr    r10
-       /* Clear the exception_marker on the stack to avoid confusing stacktrace */
+       /* Clear the exception marker on the stack to avoid confusing stacktrace */
        li      r10, 0
        stw     r10, 8(r11)
        REST_GPR(10, r11)
@@ -320,7 +320,7 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
        li      r0,0
 
        /*
-        * Leaving a stale exception_marker on the stack can confuse
+        * Leaving a stale exception marker on the stack can confuse
         * the reliable stack unwinder later on. Clear it.
         */
        stw     r0,8(r1)
@@ -372,7 +372,7 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
        mtspr   SPRN_XER,r5
 
        /*
-        * Leaving a stale exception_marker on the stack can confuse
+        * Leaving a stale exception marker on the stack can confuse
         * the reliable stack unwinder later on. Clear it.
         */
        stw     r0,8(r1)

diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index d6b7aa0..4781271 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -378,7 +378,7 @@ exc_##n##_common:                                                       \
        ld      r9,excf+EX_R1(r13);     /* load orig r1 back from PACA */   \
        lwz     r10,excf+EX_CR(r13);    /* load orig CR back from PACA  */  \
        lbz     r11,PACAIRQSOFTMASK(r13); /* get current IRQ softe */       \
-       ld      r12,exception_marker@toc(r2);                               \
+       LOAD_REG_IMMEDIATE(r12, STACK_FRAME_REGS_MARKER);                   \
        ZEROIZE_GPR(0);                                                     \
        std     r3,GPR10(r1);           /* save r10 to stackframe */        \
        std     r4,GPR11(r1);           /* save r11 to stackframe */        \
@@ -459,12 +459,6 @@ exc_##n##_bad_stack:                                                           \
        bl      hdlr;                                                   \
        b       interrupt_return
 
-/* This value is used to mark exception frames on the stack. */
-       .section        ".toc","aw"
-exception_marker:
-       .tc     ID_EXC_MARKER[TC],STACK_FRAME_REGS_MARKER
-
-
 /*
  * And here we have the exception vectors !
  */

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 43e5385..3b56fc6 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -589,7 +589,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
        li      r9,IVEC
        std     r9,_TRAP(r1)            /* set trap number              */
        li      r10,0
-       ld      r11,exception_marker@toc(r2)
+       LOAD_REG_IMMEDIATE(r11, STACK_FRAME_REGS_MARKER)
        std     r10,RESULT(r1)          /* clear regs->result           */
        std     r11,STACK_FRAME_OVERHEAD-16(r1) /* mark the frame       */
 .endm

diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index da544ea..c79da95 100644 (file)
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -192,13 +192,6 @@ __secondary_hold:
 #endif
 CLOSE_FIXED_SECTION(first_256B)
 
-/* This value is used to mark exception frames on the stack. */
-       .section ".toc","aw"
-/* This value is used to mark exception frames on the stack. */
-exception_marker:
-       .tc     ID_EXC_MARKER[TC],STACK_FRAME_REGS_MARKER
-       .previous
-
 /*
  * On server, we include the exception vectors code here as it
  * relies on absolute addressing which is only possible within

diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
index 1dfa67e..f02c559 100644 (file)
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S
@@ -80,7 +80,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name)
        /* Calling convention has r3 = regs, r4 = orig r0 */
        addi    r3,r1,STACK_FRAME_OVERHEAD
        mr      r4,r0
-       ld      r11,exception_marker@toc(r2)
+       LOAD_REG_IMMEDIATE(r11, STACK_FRAME_REGS_MARKER)
        std     r11,-16(r3)             /* "regshere" marker */
 
 BEGIN_FTR_SECTION
@@ -253,7 +253,7 @@ END_BTB_FLUSH_SECTION
        /* Calling convention has r3 = regs, r4 = orig r0 */
        addi    r3,r1,STACK_FRAME_OVERHEAD
        mr      r4,r0
-       ld      r11,exception_marker@toc(r2)
+       LOAD_REG_IMMEDIATE(r11, STACK_FRAME_REGS_MARKER)
        std     r11,-16(r3)             /* "regshere" marker */
 
 #ifdef CONFIG_PPC_BOOK3S
@@ -614,7 +614,7 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
        mtspr   SPRN_XER,r5
 
        /*
-        * Leaving a stale exception_marker on the stack can confuse
+        * Leaving a stale STACK_FRAME_REGS_MARKER on the stack can confuse
         * the reliable stack unwinder later on. Clear it.
         */
        std     r0,STACK_FRAME_OVERHEAD-16(r1)