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    SubjectRe: [PATCH v11 3/8] ARM: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL

    Hi Russell,

    I noticed that this patch set only went to the linux-arm-kernel mailing
    list but did not include you in the Cc.

    Could you give an ack to this patch, and I can take it through my tree?

    The full patch set went to linux-arm-kernel where I'm sure you have access
    to.

    Thanks!

    -- Steve


    On Sat, 8 Apr 2023 05:42:17 -0700
    Donglin Peng <pengdonglin@sangfor.com.cn> wrote:

    > 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 ARM platform.
    >
    > We introduce a new structure called fgraph_ret_regs for the ARM 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:
    > - Fix stack pointer align issues
    > - Update the commit message
    >
    > v8:
    > - Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
    > ---
    > arch/arm/Kconfig | 1 +
    > arch/arm/include/asm/ftrace.h | 22 ++++++++++++++++++++++
    > arch/arm/kernel/asm-offsets.c | 8 +++++++-
    > arch/arm/kernel/entry-ftrace.S | 10 ++++++----
    > 4 files changed, 36 insertions(+), 5 deletions(-)
    >
    > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
    > index e24a9820e12f..73061379855a 100644
    > --- a/arch/arm/Kconfig
    > +++ b/arch/arm/Kconfig
    > @@ -98,6 +98,7 @@ config ARM
    > select HAVE_FAST_GUP if ARM_LPAE
    > select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
    > select HAVE_FUNCTION_ERROR_INJECTION
    > + select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
    > select HAVE_FUNCTION_GRAPH_TRACER
    > select HAVE_FUNCTION_TRACER if !XIP_KERNEL
    > select HAVE_GCC_PLUGINS
    > diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
    > index 7e9251ca29fe..3c457902b355 100644
    > --- a/arch/arm/include/asm/ftrace.h
    > +++ b/arch/arm/include/asm/ftrace.h
    > @@ -77,4 +77,26 @@ 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 {
    > + /* r0 - r3 */
    > + unsigned long regs[4];
    > +
    > + 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_ARM_FTRACE */
    > diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c
    > index 38121c59cbc2..18bb85115b21 100644
    > --- a/arch/arm/kernel/asm-offsets.c
    > +++ b/arch/arm/kernel/asm-offsets.c
    > @@ -23,6 +23,7 @@
    > #include <asm/suspend.h>
    > #include <asm/vdso_datapage.h>
    > #include <asm/hardware/cache-l2x0.h>
    > +#include <asm/ftrace.h>
    > #include <linux/kbuild.h>
    > #include <linux/arm-smccc.h>
    > #include "signal.h"
    > @@ -170,5 +171,10 @@ int main(void)
    > DEFINE(KEXEC_INDIR_PAGE, offsetof(struct kexec_relocate_data, kexec_indirection_page));
    > DEFINE(KEXEC_MACH_TYPE, offsetof(struct kexec_relocate_data, kexec_mach_type));
    > DEFINE(KEXEC_R2, offsetof(struct kexec_relocate_data, kexec_r2));
    > - return 0;
    > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
    > + BLANK();
    > + DEFINE(FGRET_REGS_SIZE, sizeof(struct fgraph_ret_regs));
    > + BLANK();
    > +#endif
    > + return 0;
    > }
    > diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S
    > index 3e7bcaca5e07..d41a1676608c 100644
    > --- a/arch/arm/kernel/entry-ftrace.S
    > +++ b/arch/arm/kernel/entry-ftrace.S
    > @@ -257,11 +257,13 @@ ENDPROC(ftrace_graph_regs_caller)
    >
    > #ifdef CONFIG_FUNCTION_GRAPH_TRACER
    > ENTRY(return_to_handler)
    > - stmdb sp!, {r0-r3}
    > - add r0, sp, #16 @ sp at exit of instrumented routine
    > + mov ip, sp @ sp at exit of instrumented routine
    > + stmdb sp!, {r0-r3, ip, lr} @ fill fgraph_ret_regs
    > + mov r0, sp
    > bl ftrace_return_to_handler
    > - mov lr, r0 @ r0 has real ret addr
    > - ldmia sp!, {r0-r3}
    > + mov lr, r0 @ r0 has real ret addr
    > + ldmia sp, {r0-r3}
    > + add sp, sp, #FGRET_REGS_SIZE @ restore stack pointer
    > ret lr
    > ENDPROC(return_to_handler)
    > #endif

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