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    Subject[PATCH v10 4/8] arm64: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL
    Date
    The previous patch ("function_graph: Support recording and printing
    the return value of function") has laid the groundwork for the for
    the funcgraph-retval, and this modification makes it available on
    the ARM64 platform.

    We introduce a new structure called fgraph_ret_regs for the ARM64
    platform to hold return registers and the frame pointer. We then
    fill its content in the return_to_handler and pass its address to
    the function ftrace_return_to_handler to record the return value.

    Signed-off-by: Donglin Peng <pengdonglin@sangfor.com.cn>
    ---
    v10:
    - Use CONFIG_FUNCTION_GRAPH_TRACER to control fgraph_ret_regs definition

    v9:
    - Update the commit message

    v8:
    - Fix issues in ARM64 asm code
    - Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
    ---
    arch/arm64/Kconfig | 1 +
    arch/arm64/include/asm/ftrace.h | 22 ++++++++++++++++++++++
    arch/arm64/kernel/asm-offsets.c | 13 +++++++++++++
    arch/arm64/kernel/entry-ftrace.S | 27 ++++++++++++++-------------
    4 files changed, 50 insertions(+), 13 deletions(-)

    diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
    index 1023e896d46b..48856d230800 100644
    --- a/arch/arm64/Kconfig
    +++ b/arch/arm64/Kconfig
    @@ -195,6 +195,7 @@ config ARM64
    select HAVE_FTRACE_MCOUNT_RECORD
    select HAVE_FUNCTION_TRACER
    select HAVE_FUNCTION_ERROR_INJECTION
    + select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
    select HAVE_FUNCTION_GRAPH_TRACER
    select HAVE_GCC_PLUGINS
    select HAVE_HW_BREAKPOINT if PERF_EVENTS
    diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
    index 1c2672bbbf37..657adcbd80a4 100644
    --- a/arch/arm64/include/asm/ftrace.h
    +++ b/arch/arm64/include/asm/ftrace.h
    @@ -170,4 +170,26 @@ static inline bool arch_syscall_match_sym_name(const char *sym,
    }
    #endif /* ifndef __ASSEMBLY__ */

    +#ifndef __ASSEMBLY__
    +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
    +struct fgraph_ret_regs {
    + /* x0 - x7 */
    + unsigned long regs[8];
    +
    + unsigned long fp;
    + unsigned long __unused;
    +};
    +
    +static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
    +{
    + return ret_regs->regs[0];
    +}
    +
    +static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
    +{
    + return ret_regs->fp;
    +}
    +#endif /* ifdef CONFIG_FUNCTION_GRAPH_TRACER */
    +#endif
    +
    #endif /* __ASM_FTRACE_H */
    diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
    index ae345b06e9f7..75082e0409bf 100644
    --- a/arch/arm64/kernel/asm-offsets.c
    +++ b/arch/arm64/kernel/asm-offsets.c
    @@ -197,6 +197,19 @@ int main(void)
    #endif
    #ifdef CONFIG_FUNCTION_TRACER
    DEFINE(FTRACE_OPS_FUNC, offsetof(struct ftrace_ops, func));
    +#endif
    + BLANK();
    +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
    + DEFINE(FGRET_REGS_X0, offsetof(struct fgraph_ret_regs, regs[0]));
    + DEFINE(FGRET_REGS_X1, offsetof(struct fgraph_ret_regs, regs[1]));
    + DEFINE(FGRET_REGS_X2, offsetof(struct fgraph_ret_regs, regs[2]));
    + DEFINE(FGRET_REGS_X3, offsetof(struct fgraph_ret_regs, regs[3]));
    + DEFINE(FGRET_REGS_X4, offsetof(struct fgraph_ret_regs, regs[4]));
    + DEFINE(FGRET_REGS_X5, offsetof(struct fgraph_ret_regs, regs[5]));
    + DEFINE(FGRET_REGS_X6, offsetof(struct fgraph_ret_regs, regs[6]));
    + DEFINE(FGRET_REGS_X7, offsetof(struct fgraph_ret_regs, regs[7]));
    + DEFINE(FGRET_REGS_FP, offsetof(struct fgraph_ret_regs, fp));
    + DEFINE(FGRET_REGS_SIZE, sizeof(struct fgraph_ret_regs));
    #endif
    return 0;
    }
    diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S
    index 350ed81324ac..da1443bcf776 100644
    --- a/arch/arm64/kernel/entry-ftrace.S
    +++ b/arch/arm64/kernel/entry-ftrace.S
    @@ -270,22 +270,23 @@ SYM_FUNC_END(ftrace_stub_graph)
    */
    SYM_CODE_START(return_to_handler)
    /* save return value regs */
    - sub sp, sp, #64
    - stp x0, x1, [sp]
    - stp x2, x3, [sp, #16]
    - stp x4, x5, [sp, #32]
    - stp x6, x7, [sp, #48]
    + sub sp, sp, #FGRET_REGS_SIZE
    + stp x0, x1, [sp, #FGRET_REGS_X0]
    + stp x2, x3, [sp, #FGRET_REGS_X2]
    + stp x4, x5, [sp, #FGRET_REGS_X4]
    + stp x6, x7, [sp, #FGRET_REGS_X6]
    + str x29, [sp, #FGRET_REGS_FP] // parent's fp

    - mov x0, x29 // parent's fp
    - bl ftrace_return_to_handler// addr = ftrace_return_to_hander(fp);
    - mov x30, x0 // restore the original return address
    + mov x0, sp
    + bl ftrace_return_to_handler // addr = ftrace_return_to_hander(regs);
    + mov x30, x0 // restore the original return address

    /* restore return value regs */
    - ldp x0, x1, [sp]
    - ldp x2, x3, [sp, #16]
    - ldp x4, x5, [sp, #32]
    - ldp x6, x7, [sp, #48]
    - add sp, sp, #64
    + ldp x0, x1, [sp, #FGRET_REGS_X0]
    + ldp x2, x3, [sp, #FGRET_REGS_X2]
    + ldp x4, x5, [sp, #FGRET_REGS_X4]
    + ldp x6, x7, [sp, #FGRET_REGS_X6]
    + add sp, sp, #FGRET_REGS_SIZE

    ret
    SYM_CODE_END(return_to_handler)
    --
    2.25.1
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