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    Subject[PATCH 6/9] ftrace, ia64: IA64 dynamic ftrace support
    From: Shaohua Li <shaohua.li@intel.com>

    IA64 dynamic ftrace support.
    The original _mcount stub for each function is like:
    alloc r40=ar.pfs,12,8,0
    mov r43=r0;;
    mov r42=b0
    mov r41=r1
    nop.i 0x0
    br.call.sptk.many b0 = _mcount;;

    The patch convert it to below for nop:
    [MII] nop.m 0x0
    mov r3=ip
    nop.i 0x0
    [MLX] nop.m 0x0
    nop.x 0x0;;
    This isn't completely nop, as there is one instuction 'mov r3=ip', but
    it should be light and harmless for code follow it.

    And below is for call
    [MII] nop.m 0x0
    mov r3=ip
    nop.i 0x0
    [MLX] nop.m 0x0
    brl.many .;;
    In this way, only one instruction is changed to convert code between nop
    and call. This should meet dyn-ftrace's requirement.
    But this requires CPU support brl instruction, so dyn-ftrace isn't
    supported for old Itanium system. Assume there are quite few such old
    system running.

    Signed-off-by: Shaohua Li <shaohua.li@intel.com>
    Signed-off-by: Steven Rostedt <srostedt@redhat.com>
    ---
    arch/ia64/Kconfig | 2 +
    arch/ia64/include/asm/ftrace.h | 13 +++
    arch/ia64/kernel/Makefile | 5 +
    arch/ia64/kernel/entry.S | 51 ++++++++++
    arch/ia64/kernel/ftrace.c | 206 ++++++++++++++++++++++++++++++++++++++++
    5 files changed, 277 insertions(+), 0 deletions(-)
    create mode 100644 arch/ia64/kernel/ftrace.c

    diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
    index b992ba4..e20c1d4 100644
    --- a/arch/ia64/Kconfig
    +++ b/arch/ia64/Kconfig
    @@ -21,6 +21,8 @@ config IA64
    select HAVE_OPROFILE
    select HAVE_KPROBES
    select HAVE_KRETPROBES
    + select HAVE_FTRACE_MCOUNT_RECORD
    + select HAVE_DYNAMIC_FTRACE if (!ITANIUM)
    select HAVE_FUNCTION_TRACER
    select HAVE_DMA_ATTRS
    select HAVE_KVM
    diff --git a/arch/ia64/include/asm/ftrace.h b/arch/ia64/include/asm/ftrace.h
    index 48694b3..d20db3c 100644
    --- a/arch/ia64/include/asm/ftrace.h
    +++ b/arch/ia64/include/asm/ftrace.h
    @@ -8,6 +8,19 @@
    extern void _mcount(unsigned long pfs, unsigned long r1, unsigned long b0, unsigned long r0);
    #define mcount _mcount

    +#include <asm/kprobes.h>
    +/* In IA64, MCOUNT_ADDR is set in link time, so it's not a constant at compile time */
    +#define MCOUNT_ADDR (((struct fnptr *)mcount)->ip)
    +#define FTRACE_ADDR (((struct fnptr *)ftrace_caller)->ip)
    +
    +static inline unsigned long ftrace_call_adjust(unsigned long addr)
    +{
    + /* second bundle, insn 2 */
    + return addr - 0x12;
    +}
    +
    +struct dyn_arch_ftrace {
    +};
    #endif

    #endif /* CONFIG_FUNCTION_TRACER */
    diff --git a/arch/ia64/kernel/Makefile b/arch/ia64/kernel/Makefile
    index f2778f2..dc62df0 100644
    --- a/arch/ia64/kernel/Makefile
    +++ b/arch/ia64/kernel/Makefile
    @@ -2,6 +2,10 @@
    # Makefile for the linux kernel.
    #

    +ifdef CONFIG_DYNAMIC_FTRACE
    +CFLAGS_REMOVE_ftrace.o = -pg
    +endif
    +
    extra-y := head.o init_task.o vmlinux.lds

    obj-y := acpi.o entry.o efi.o efi_stub.o gate-data.o fsys.o ia64_ksyms.o irq.o irq_ia64.o \
    @@ -28,6 +32,7 @@ obj-$(CONFIG_IA64_CYCLONE) += cyclone.o
    obj-$(CONFIG_CPU_FREQ) += cpufreq/
    obj-$(CONFIG_IA64_MCA_RECOVERY) += mca_recovery.o
    obj-$(CONFIG_KPROBES) += kprobes.o jprobes.o
    +obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
    obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o crash.o
    obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
    obj-$(CONFIG_IA64_UNCACHED_ALLOCATOR) += uncached.o
    diff --git a/arch/ia64/kernel/entry.S b/arch/ia64/kernel/entry.S
    index c2f7d79..e0be92a 100644
    --- a/arch/ia64/kernel/entry.S
    +++ b/arch/ia64/kernel/entry.S
    @@ -1406,6 +1406,56 @@ GLOBAL_ENTRY(unw_init_running)
    END(unw_init_running)

    #ifdef CONFIG_FUNCTION_TRACER
    +#ifdef CONFIG_DYNAMIC_FTRACE
    +GLOBAL_ENTRY(_mcount)
    + br ftrace_stub
    +END(_mcount)
    +
    +.here:
    + br.ret.sptk.many b0
    +
    +GLOBAL_ENTRY(ftrace_caller)
    + alloc out0 = ar.pfs, 8, 0, 4, 0
    + mov out3 = r0
    + ;;
    + mov out2 = b0
    + add r3 = 0x20, r3
    + mov out1 = r1;
    + br.call.sptk.many b0 = ftrace_patch_gp
    + //this might be called from module, so we must patch gp
    +ftrace_patch_gp:
    + movl gp=__gp
    + mov b0 = r3
    + ;;
    +.global ftrace_call;
    +ftrace_call:
    +{
    + .mlx
    + nop.m 0x0
    + movl r3 = .here;;
    +}
    + alloc loc0 = ar.pfs, 4, 4, 2, 0
    + ;;
    + mov loc1 = b0
    + mov out0 = b0
    + mov loc2 = r8
    + mov loc3 = r15
    + ;;
    + adds out0 = -MCOUNT_INSN_SIZE, out0
    + mov out1 = in2
    + mov b6 = r3
    +
    + br.call.sptk.many b0 = b6
    + ;;
    + mov ar.pfs = loc0
    + mov b0 = loc1
    + mov r8 = loc2
    + mov r15 = loc3
    + br ftrace_stub
    + ;;
    +END(ftrace_caller)
    +
    +#else
    GLOBAL_ENTRY(_mcount)
    movl r2 = ftrace_stub
    movl r3 = ftrace_trace_function;;
    @@ -1435,6 +1485,7 @@ GLOBAL_ENTRY(_mcount)
    br ftrace_stub
    ;;
    END(_mcount)
    +#endif

    GLOBAL_ENTRY(ftrace_stub)
    mov r3 = b0
    diff --git a/arch/ia64/kernel/ftrace.c b/arch/ia64/kernel/ftrace.c
    new file mode 100644
    index 0000000..7fc8c96
    --- /dev/null
    +++ b/arch/ia64/kernel/ftrace.c
    @@ -0,0 +1,206 @@
    +/*
    + * Dynamic function tracing support.
    + *
    + * Copyright (C) 2008 Shaohua Li <shaohua.li@intel.com>
    + *
    + * For licencing details, see COPYING.
    + *
    + * Defines low-level handling of mcount calls when the kernel
    + * is compiled with the -pg flag. When using dynamic ftrace, the
    + * mcount call-sites get patched lazily with NOP till they are
    + * enabled. All code mutation routines here take effect atomically.
    + */
    +
    +#include <linux/uaccess.h>
    +#include <linux/ftrace.h>
    +
    +#include <asm/cacheflush.h>
    +#include <asm/patch.h>
    +
    +/* In IA64, each function will be added below two bundles with -pg option */
    +static unsigned char __attribute__((aligned(8)))
    +ftrace_orig_code[MCOUNT_INSN_SIZE] = {
    + 0x02, 0x40, 0x31, 0x10, 0x80, 0x05, /* alloc r40=ar.pfs,12,8,0 */
    + 0xb0, 0x02, 0x00, 0x00, 0x42, 0x40, /* mov r43=r0;; */
    + 0x05, 0x00, 0xc4, 0x00, /* mov r42=b0 */
    + 0x11, 0x48, 0x01, 0x02, 0x00, 0x21, /* mov r41=r1 */
    + 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, /* nop.i 0x0 */
    + 0x08, 0x00, 0x00, 0x50 /* br.call.sptk.many b0 = _mcount;; */
    +};
    +
    +struct ftrace_orig_insn {
    + u64 dummy1, dummy2, dummy3;
    + u64 dummy4:64-41+13;
    + u64 imm20:20;
    + u64 dummy5:3;
    + u64 sign:1;
    + u64 dummy6:4;
    +};
    +
    +/* mcount stub will be converted below for nop */
    +static unsigned char ftrace_nop_code[MCOUNT_INSN_SIZE] = {
    + 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MII] nop.m 0x0 */
    + 0x30, 0x00, 0x00, 0x60, 0x00, 0x00, /* mov r3=ip */
    + 0x00, 0x00, 0x04, 0x00, /* nop.i 0x0 */
    + 0x05, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MLX] nop.m 0x0 */
    + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* nop.x 0x0;; */
    + 0x00, 0x00, 0x04, 0x00
    +};
    +
    +static unsigned char *ftrace_nop_replace(void)
    +{
    + return ftrace_nop_code;
    +}
    +
    +/*
    + * mcount stub will be converted below for call
    + * Note: Just the last instruction is changed against nop
    + * */
    +static unsigned char __attribute__((aligned(8)))
    +ftrace_call_code[MCOUNT_INSN_SIZE] = {
    + 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MII] nop.m 0x0 */
    + 0x30, 0x00, 0x00, 0x60, 0x00, 0x00, /* mov r3=ip */
    + 0x00, 0x00, 0x04, 0x00, /* nop.i 0x0 */
    + 0x05, 0x00, 0x00, 0x00, 0x01, 0x00, /* [MLX] nop.m 0x0 */
    + 0xff, 0xff, 0xff, 0xff, 0x7f, 0x00, /* brl.many .;;*/
    + 0xf8, 0xff, 0xff, 0xc8
    +};
    +
    +struct ftrace_call_insn {
    + u64 dummy1, dummy2;
    + u64 dummy3:48;
    + u64 imm39_l:16;
    + u64 imm39_h:23;
    + u64 dummy4:13;
    + u64 imm20:20;
    + u64 dummy5:3;
    + u64 i:1;
    + u64 dummy6:4;
    +};
    +
    +static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
    +{
    + struct ftrace_call_insn *code = (void *)ftrace_call_code;
    + unsigned long offset = addr - (ip + 0x10);
    +
    + code->imm39_l = offset >> 24;
    + code->imm39_h = offset >> 40;
    + code->imm20 = offset >> 4;
    + code->i = offset >> 63;
    + return ftrace_call_code;
    +}
    +
    +static int
    +ftrace_modify_code(unsigned long ip, unsigned char *old_code,
    + unsigned char *new_code, int do_check)
    +{
    + unsigned char replaced[MCOUNT_INSN_SIZE];
    +
    + /*
    + * Note: Due to modules and __init, code can
    + * disappear and change, we need to protect against faulting
    + * as well as code changing. We do this by using the
    + * probe_kernel_* functions.
    + *
    + * No real locking needed, this code is run through
    + * kstop_machine, or before SMP starts.
    + */
    +
    + if (!do_check)
    + goto skip_check;
    +
    + /* read the text we want to modify */
    + if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
    + return -EFAULT;
    +
    + /* Make sure it is what we expect it to be */
    + if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
    + return -EINVAL;
    +
    +skip_check:
    + /* replace the text with the new text */
    + if (probe_kernel_write(((void *)ip), new_code, MCOUNT_INSN_SIZE))
    + return -EPERM;
    + flush_icache_range(ip, ip + MCOUNT_INSN_SIZE);
    +
    + return 0;
    +}
    +
    +static int ftrace_make_nop_check(struct dyn_ftrace *rec, unsigned long addr)
    +{
    + unsigned char __attribute__((aligned(8))) replaced[MCOUNT_INSN_SIZE];
    + unsigned long ip = rec->ip;
    +
    + if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
    + return -EFAULT;
    + if (rec->flags & FTRACE_FL_CONVERTED) {
    + struct ftrace_call_insn *call_insn, *tmp_call;
    +
    + call_insn = (void *)ftrace_call_code;
    + tmp_call = (void *)replaced;
    + call_insn->imm39_l = tmp_call->imm39_l;
    + call_insn->imm39_h = tmp_call->imm39_h;
    + call_insn->imm20 = tmp_call->imm20;
    + call_insn->i = tmp_call->i;
    + if (memcmp(replaced, ftrace_call_code, MCOUNT_INSN_SIZE) != 0)
    + return -EINVAL;
    + return 0;
    + } else {
    + struct ftrace_orig_insn *call_insn, *tmp_call;
    +
    + call_insn = (void *)ftrace_orig_code;
    + tmp_call = (void *)replaced;
    + call_insn->sign = tmp_call->sign;
    + call_insn->imm20 = tmp_call->imm20;
    + if (memcmp(replaced, ftrace_orig_code, MCOUNT_INSN_SIZE) != 0)
    + return -EINVAL;
    + return 0;
    + }
    +}
    +
    +int ftrace_make_nop(struct module *mod,
    + struct dyn_ftrace *rec, unsigned long addr)
    +{
    + int ret;
    + char *new;
    +
    + ret = ftrace_make_nop_check(rec, addr);
    + if (ret)
    + return ret;
    + new = ftrace_nop_replace();
    + return ftrace_modify_code(rec->ip, NULL, new, 0);
    +}
    +
    +int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
    +{
    + unsigned long ip = rec->ip;
    + unsigned char *old, *new;
    +
    + old= ftrace_nop_replace();
    + new = ftrace_call_replace(ip, addr);
    + return ftrace_modify_code(ip, old, new, 1);
    +}
    +
    +/* in IA64, _mcount can't directly call ftrace_stub. Only jump is ok */
    +int ftrace_update_ftrace_func(ftrace_func_t func)
    +{
    + unsigned long ip;
    + unsigned long addr = ((struct fnptr *)ftrace_call)->ip;
    +
    + if (func == ftrace_stub)
    + return 0;
    + ip = ((struct fnptr *)func)->ip;
    +
    + ia64_patch_imm64(addr + 2, ip);
    +
    + flush_icache_range(addr, addr + 16);
    + return 0;
    +}
    +
    +/* run from kstop_machine */
    +int __init ftrace_dyn_arch_init(void *data)
    +{
    + *(unsigned long *)data = 0;
    +
    + return 0;
    +}
    --
    1.5.6.5
    --


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