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    Subject[PATCH v9 08/10] tracing: make ftrace for MIPS work without -fno-omit-frame-pointer
    Date
    From: Wu Zhangjin <wuzhangjin@gmail.com>

    When remove the -fno-omit-frame-pointer, gcc will not save the frame
    pointer for us, we need to save one ourselves.

    Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
    ---
    arch/mips/include/asm/ftrace.h | 57 ++++++++++++++++++++++++++++++++++++++++
    arch/mips/kernel/ftrace.c | 56 ++++++++++++++++++++++++++++----------
    arch/mips/kernel/mcount.S | 8 +++++
    3 files changed, 106 insertions(+), 15 deletions(-)

    diff --git a/arch/mips/include/asm/ftrace.h b/arch/mips/include/asm/ftrace.h
    index 7094a40..3986cd8 100644
    --- a/arch/mips/include/asm/ftrace.h
    +++ b/arch/mips/include/asm/ftrace.h
    @@ -19,6 +19,62 @@
    extern void _mcount(void);
    #define mcount _mcount

    +#define safe_load(load, src, dst, error) \
    +do { \
    + asm volatile ( \
    + "1: " load " %[" STR(dst) "], 0(%[" STR(src) "])\n"\
    + " li %[" STR(error) "], 0\n" \
    + "2:\n" \
    + \
    + ".section .fixup, \"ax\"\n" \
    + "3: li %[" STR(error) "], 1\n" \
    + " j 2b\n" \
    + ".previous\n" \
    + \
    + ".section\t__ex_table,\"a\"\n\t" \
    + STR(PTR) "\t1b, 3b\n\t" \
    + ".previous\n" \
    + \
    + : [dst] "=&r" (dst), [error] "=r" (error)\
    + : [src] "r" (src) \
    + : "memory" \
    + ); \
    +} while (0)
    +
    +#define safe_store(store, src, dst, error) \
    +do { \
    + asm volatile ( \
    + "1: " store " %[" STR(src) "], 0(%[" STR(dst) "])\n"\
    + " li %[" STR(error) "], 0\n" \
    + "2:\n" \
    + \
    + ".section .fixup, \"ax\"\n" \
    + "3: li %[" STR(error) "], 1\n" \
    + " j 2b\n" \
    + ".previous\n" \
    + \
    + ".section\t__ex_table,\"a\"\n\t"\
    + STR(PTR) "\t1b, 3b\n\t" \
    + ".previous\n" \
    + \
    + : [error] "=r" (error) \
    + : [dst] "r" (dst), [src] "r" (src)\
    + : "memory" \
    + ); \
    +} while (0)
    +
    +#define safe_load_code(dst, src, error) \
    + safe_load(STR(lw), src, dst, error)
    +#define safe_store_code(src, dst, error) \
    + safe_store(STR(sw), src, dst, error)
    +
    +#define safe_load_stack(dst, src, error) \
    + safe_load(STR(PTR_L), src, dst, error)
    +
    +#define safe_store_stack(src, dst, error) \
    + safe_store(STR(PTR_S), src, dst, error)
    +
    +
    #ifdef CONFIG_DYNAMIC_FTRACE
    static inline unsigned long ftrace_call_adjust(unsigned long addr)
    {
    @@ -27,6 +83,7 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)

    struct dyn_arch_ftrace {
    };
    +
    #endif /* CONFIG_DYNAMIC_FTRACE */
    #endif /* __ASSEMBLY__ */
    #endif /* CONFIG_FUNCTION_TRACER */
    diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
    index e981a49..e363fc6 100644
    --- a/arch/mips/kernel/ftrace.c
    +++ b/arch/mips/kernel/ftrace.c
    @@ -27,7 +27,13 @@ static unsigned int ftrace_nop = 0x00000000;

    static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
    {
    - *(unsigned int *)ip = new_code;
    + int faulted;
    +
    + /* *(unsigned int *)ip = new_code; */
    + safe_store_code(new_code, ip, faulted);
    +
    + if (unlikely(faulted))
    + return -EFAULT;

    flush_icache_range(ip, ip + 8);

    @@ -41,14 +47,20 @@ int ftrace_make_nop(struct module *mod,
    struct dyn_ftrace *rec, unsigned long addr)
    {
    unsigned int new;
    + int faulted;
    unsigned long ip = rec->ip;

    /* We have compiled module with -mlong-calls, but compiled the kernel
    * without it, we need to cope with them respectively. */
    if (ip & 0x40000000) {
    /* record it for ftrace_make_call */
    - if (lui_v1 == 0)
    - lui_v1 = *(unsigned int *)ip;
    + if (lui_v1 == 0) {
    + /* lui_v1 = *(unsigned int *)ip; */
    + safe_load_code(lui_v1, ip, faulted);
    +
    + if (unlikely(faulted))
    + return -EFAULT;
    + }

    /* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
    * addiu v1, v1, low_16bit_of_mcount
    @@ -147,6 +159,7 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
    {
    unsigned long sp, ip, ra;
    unsigned int code;
    + int faulted;

    /* in module or kernel? */
    if (self_addr & 0x40000000) {
    @@ -162,8 +175,11 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
    do {
    ip -= 4;

    - /* get the code at "ip" */
    - code = *(unsigned int *)ip;
    + /* get the code at "ip": code = *(unsigned int *)ip; */
    + safe_load_code(code, ip, faulted);
    +
    + if (unlikely(faulted))
    + return 0;

    /* If we hit the non-store instruction before finding where the
    * ra is stored, then this is a leaf function and it does not
    @@ -174,11 +190,14 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
    } while (((code & S_RA_SP) != S_RA_SP));

    sp = fp + (code & OFFSET_MASK);
    - ra = *(unsigned long *)sp;
    +
    + /* ra = *(unsigned long *)sp; */
    + safe_load_stack(ra, sp, faulted);
    + if (unlikely(faulted))
    + return 0;

    if (ra == parent)
    return sp;
    -
    return 0;
    }

    @@ -193,6 +212,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
    struct ftrace_graph_ent trace;
    unsigned long return_hooker = (unsigned long)
    &return_to_handler;
    + int faulted;

    if (unlikely(atomic_read(&current->tracing_graph_pause)))
    return;
    @@ -206,21 +226,23 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
    * ftrace_get_parent_addr() does it!
    */

    - old = *parent;
    + /* old = *parent; */
    + safe_load_stack(old, parent, faulted);
    + if (unlikely(faulted))
    + goto out;

    parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old,
    (unsigned long)parent,
    fp);
    -
    /* If fails when getting the stack address of the non-leaf function's
    * ra, stop function graph tracer and return */
    - if (parent == 0) {
    - ftrace_graph_stop();
    - WARN_ON(1);
    - return;
    - }
    + if (parent == 0)
    + goto out;

    - *parent = return_hooker;
    + /* *parent = return_hooker; */
    + safe_store_stack(return_hooker, parent, faulted);
    + if (unlikely(faulted))
    + goto out;

    if (ftrace_push_return_trace(old, self_addr, &trace.depth, fp) ==
    -EBUSY) {
    @@ -235,5 +257,9 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
    current->curr_ret_stack--;
    *parent = old;
    }
    + return;
    +out:
    + ftrace_graph_stop();
    + WARN_ON(1);
    }
    #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
    diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
    index 98d4690..bdfef2c 100644
    --- a/arch/mips/kernel/mcount.S
    +++ b/arch/mips/kernel/mcount.S
    @@ -139,7 +139,15 @@ NESTED(ftrace_graph_caller, PT_SIZE, ra)
    #endif
    PTR_LA a0, PT_R1(sp) /* arg1: &AT -> a0 */
    jal prepare_ftrace_return
    +#ifdef CONFIG_FRAME_POINTER
    move a2, fp /* arg3: frame pointer */
    +#else
    +#ifdef CONFIG_64BIT
    + PTR_LA a2, PT_SIZE(sp)
    +#else
    + PTR_LA a2, (PT_SIZE+8)(sp)
    +#endif
    +#endif

    MCOUNT_RESTORE_REGS
    RETURN_BACK
    --
    1.6.2.1


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