powerpc/64: avoid using r13 in relocate

relocate() uses r13 in early boot before it is used for the paca. Use
a different register for this so r13 is kept unchanged until it is
set to the paca pointer.

Avoid r14 as well while we're here, there's no reason not to use the
volatile registers which is a bit less surprising, and r14 could be used
as another fixed reg one day.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220926055620.2676869-4-npiggin@gmail.com

diff --git a/arch/powerpc/kernel/reloc_64.S b/arch/powerpc/kernel/reloc_64.S
index 232e4549defe1f79b78f148bf94989565b45d973..efd52f2e70339919535983e86a143f62f6a17f47 100644 (file)
--- a/arch/powerpc/kernel/reloc_64.S
+++ b/arch/powerpc/kernel/reloc_64.S
@@ -27,8 +27,8 @@ _GLOBAL(relocate)
        add     r9,r9,r12       /* r9 has runtime addr of .rela.dyn section */
        ld      r10,(p_st - 0b)(r12)
        add     r10,r10,r12     /* r10 has runtime addr of _stext */
-       ld      r13,(p_sym - 0b)(r12)
-       add     r13,r13,r12     /* r13 has runtime addr of .dynsym */
+       ld      r4,(p_sym - 0b)(r12)
+       add     r4,r4,r12       /* r4 has runtime addr of .dynsym */
 
        /*
         * Scan the dynamic section for the RELA, RELASZ and RELAENT entries.
@@ -84,16 +84,16 @@ _GLOBAL(relocate)
        ld      r0,16(r9)       /* reloc->r_addend */
        b       .Lstore
 .Luaddr64:
-       srdi    r14,r0,32       /* ELF64_R_SYM(reloc->r_info) */
+       srdi    r5,r0,32        /* ELF64_R_SYM(reloc->r_info) */
        clrldi  r0,r0,32
        cmpdi   r0,R_PPC64_UADDR64
        bne     .Lnext
        ld      r6,0(r9)
        ld      r0,16(r9)
-       mulli   r14,r14,24      /* 24 == sizeof(elf64_sym) */
-       add     r14,r14,r13     /* elf64_sym[ELF64_R_SYM] */
-       ld      r14,8(r14)
-       add     r0,r0,r14
+       mulli   r5,r5,24        /* 24 == sizeof(elf64_sym) */
+       add     r5,r5,r4        /* elf64_sym[ELF64_R_SYM] */
+       ld      r5,8(r5)
+       add     r0,r0,r5
 .Lstore:
        add     r0,r0,r3
        stdx    r0,r7,r6