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    SubjectRe: [RFC/PATCH 3/3] ARM: Replace calls to __aeabi_{u}idiv with udiv/sdiv instructions
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    Stephen Boyd <sboyd@codeaurora.org> writes:

    > +static int module_patch_aeabi_uidiv(unsigned long loc, const Elf32_Sym *sym)
    > +{
    > + extern char __aeabi_uidiv[], __aeabi_idiv[];
    > + unsigned long udiv_addr = (unsigned long)__aeabi_uidiv;
    > + unsigned long sdiv_addr = (unsigned long)__aeabi_idiv;
    > + unsigned int udiv_insn, sdiv_insn, mask;
    > +
    > + if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
    > + mask = HWCAP_IDIVT;
    > + udiv_insn = __opcode_to_mem_thumb32(0xfbb0f0f1);
    > + sdiv_insn = __opcode_to_mem_thumb32(0xfb90f0f1);
    > + } else {
    > + mask = HWCAP_IDIVA;
    > + udiv_insn = __opcode_to_mem_arm(0xe730f110);
    > + sdiv_insn = __opcode_to_mem_arm(0xe710f110);
    > + }
    > +
    > + if (elf_hwcap & mask) {
    > + if (sym->st_value == udiv_addr) {
    > + *(u32 *)loc = udiv_insn;
    > + return 1;
    > + } else if (sym->st_value == sdiv_addr) {
    > + *(u32 *)loc = sdiv_insn;
    > + return 1;
    > + }
    > + }
    > +
    > + return 0;
    > +}

    [...]

    > +static void __init patch_aeabi_uidiv(void)
    > +{
    > + extern unsigned long *__start_udiv_loc[], *__stop_udiv_loc[];
    > + extern unsigned long *__start_idiv_loc[], *__stop_idiv_loc[];
    > + unsigned long **p;
    > + unsigned int udiv_insn, sdiv_insn, mask;
    > +
    > + if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
    > + mask = HWCAP_IDIVT;
    > + udiv_insn = __opcode_to_mem_thumb32(0xfbb0f0f1);
    > + sdiv_insn = __opcode_to_mem_thumb32(0xfb90f0f1);
    > + } else {
    > + mask = HWCAP_IDIVA;
    > + udiv_insn = __opcode_to_mem_arm(0xe730f110);
    > + sdiv_insn = __opcode_to_mem_arm(0xe710f110);
    > + }
    > +
    > + if (elf_hwcap & mask) {
    > + for (p = __start_udiv_loc; p < __stop_udiv_loc; p++) {
    > + unsigned long *inst = *p;
    > + *inst = udiv_insn;
    > + }
    > + for (p = __start_idiv_loc; p < __stop_idiv_loc; p++) {
    > + unsigned long *inst = *p;
    > + *inst = sdiv_insn;
    > + }
    > + }
    > +}

    These functions are rather similar. Perhaps they could be combined
    somehow.

    --
    Måns Rullgård
    mans@mansr.com


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