Re: [PATCH v6 5/9] LoongArch/ftrace: Add DYNAMIC_FTRACE_WITH_REGS support

[Huacai Chen]

On Tue, Nov 15, 2022 at 5:22 PM Qing Zhang <zhangqing@xxxxxxxxxxx> wrote:
>
> Hi, Huacai
>
> On 2022/11/15 下午4:41, Huacai Chen wrote:
> > Hi, Qing,
> >
> > Patch5 and Patch6 are small and related, maybe they can be combined
> > with a name "LoongArch/ftrace: Add DYNAMIC_FTRACE_WITH_{ARGS,REGS}
> > support"
> I think they should be independent due to different use scenarios.
>From the commit message it seems  DYNAMIC_FTRACE_WITH_ARGS depend on
DYNAMIC_FTRACE_WITH_REGS.

Huacai
>
> Thanks,
> -Qing
> >
> > Huacai
> >
> > On Tue, Nov 15, 2022 at 10:55 AM Qing Zhang <zhangqing@xxxxxxxxxxx> wrote:
> >>
> >> This patch implements DYNAMIC_FTRACE_WITH_REGS on LoongArch, which allows
> >> a traced function's arguments (and some other registers) to be captured
> >> into a struct pt_regs, allowing these to be inspected and modified.
> >>
> >> Co-developed-by: Jinyang He <hejinyang@xxxxxxxxxxx>
> >> Signed-off-by: Jinyang He <hejinyang@xxxxxxxxxxx>
> >> Signed-off-by: Qing Zhang <zhangqing@xxxxxxxxxxx>
> >> ---
> >>   arch/loongarch/Kconfig              |  1 +
> >>   arch/loongarch/include/asm/ftrace.h |  3 +++
> >>   arch/loongarch/kernel/ftrace_dyn.c  | 17 ++++++++++++++
> >>   arch/loongarch/kernel/mcount-dyn.S  | 36 +++++++++++++++++++++++++++--
> >>   4 files changed, 55 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> >> index 615ce62422b8..12e3e91a68ae 100644
> >> --- a/arch/loongarch/Kconfig
> >> +++ b/arch/loongarch/Kconfig
> >> @@ -90,6 +90,7 @@ config LOONGARCH
> >>          select HAVE_DEBUG_STACKOVERFLOW
> >>          select HAVE_DMA_CONTIGUOUS
> >>          select HAVE_DYNAMIC_FTRACE
> >> +       select HAVE_DYNAMIC_FTRACE_WITH_REGS
> >>          select HAVE_EBPF_JIT
> >>          select HAVE_EXIT_THREAD
> >>          select HAVE_FAST_GUP
> >> diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
> >> index 76ca58767f4d..a3f974a7a5ce 100644
> >> --- a/arch/loongarch/include/asm/ftrace.h
> >> +++ b/arch/loongarch/include/asm/ftrace.h
> >> @@ -28,6 +28,9 @@ struct dyn_ftrace;
> >>   int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
> >>   #define ftrace_init_nop ftrace_init_nop
> >>
> >> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> >> +#define ARCH_SUPPORTS_FTRACE_OPS 1
> >> +#endif
> >>   #endif /* CONFIG_DYNAMIC_FTRACE */
> >>   #endif /* __ASSEMBLY__ */
> >>   #endif /* CONFIG_FUNCTION_TRACER */
> >> diff --git a/arch/loongarch/kernel/ftrace_dyn.c b/arch/loongarch/kernel/ftrace_dyn.c
> >> index 3fe791b6783e..ec3d951be50c 100644
> >> --- a/arch/loongarch/kernel/ftrace_dyn.c
> >> +++ b/arch/loongarch/kernel/ftrace_dyn.c
> >> @@ -99,6 +99,23 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
> >>          return ftrace_modify_code(pc, old, new, true);
> >>   }
> >>
> >> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> >> +int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
> >> +                       unsigned long addr)
> >> +{
> >> +       unsigned long pc;
> >> +       long offset;
> >> +       u32 old, new;
> >> +
> >> +       pc = rec->ip + LOONGARCH_INSN_SIZE;
> >> +
> >> +       old = larch_insn_gen_bl(pc, old_addr);
> >> +       new = larch_insn_gen_bl(pc, addr);
> >> +
> >> +       return ftrace_modify_code(pc, old, new, true);
> >> +}
> >> +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
> >> +
> >>   void arch_ftrace_update_code(int command)
> >>   {
> >>          command |= FTRACE_MAY_SLEEP;
> >> diff --git a/arch/loongarch/kernel/mcount-dyn.S b/arch/loongarch/kernel/mcount-dyn.S
> >> index 0c12cc108e6f..02835186b463 100644
> >> --- a/arch/loongarch/kernel/mcount-dyn.S
> >> +++ b/arch/loongarch/kernel/mcount-dyn.S
> >> @@ -27,7 +27,7 @@
> >>    * follows the LoongArch psABI well.
> >>    */
> >>
> >> -       .macro  ftrace_regs_entry
> >> +       .macro  ftrace_regs_entry allregs=0
> >>          PTR_ADDI sp, sp, -PT_SIZE
> >>          /* Save trace function ra at PT_ERA */
> >>          PTR_S   ra, sp, PT_ERA
> >> @@ -43,16 +43,48 @@
> >>          PTR_S   a7, sp, PT_R11
> >>          PTR_S   fp, sp, PT_R22
> >>
> >> +       .if \allregs
> >> +       PTR_S   t0, sp, PT_R12
> >> +       PTR_S   t1, sp, PT_R13
> >> +       PTR_S   t2, sp, PT_R14
> >> +       PTR_S   t3, sp, PT_R15
> >> +       PTR_S   t4, sp, PT_R16
> >> +       PTR_S   t5, sp, PT_R17
> >> +       PTR_S   t6, sp, PT_R18
> >> +       PTR_S   t7, sp, PT_R19
> >> +       PTR_S   t8, sp, PT_R20
> >> +       PTR_S   s0, sp, PT_R23
> >> +       PTR_S   s1, sp, PT_R24
> >> +       PTR_S   s2, sp, PT_R25
> >> +       PTR_S   s3, sp, PT_R26
> >> +       PTR_S   s4, sp, PT_R27
> >> +       PTR_S   s5, sp, PT_R28
> >> +       PTR_S   s6, sp, PT_R29
> >> +       PTR_S   s7, sp, PT_R30
> >> +       PTR_S   s8, sp, PT_R31
> >> +       PTR_S   tp, sp, PT_R2
> >> +       /* Clear it for later use as a flag sometimes. */
> >> +       PTR_S   zero, sp, PT_R0
> >> +       PTR_S   $r21, sp, PT_R21
> >> +       .endif
> >> +
> >>          PTR_ADDI t8, sp, PT_SIZE
> >>          PTR_S   t8, sp, PT_R3
> >>
> >>          .endm
> >>
> >>   SYM_CODE_START(ftrace_caller)
> >> -       ftrace_regs_entry
> >> +       ftrace_regs_entry allregs=0
> >>          b       ftrace_common
> >>   SYM_CODE_END(ftrace_caller)
> >>
> >> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> >> +SYM_CODE_START(ftrace_regs_caller)
> >> +       ftrace_regs_entry allregs=1
> >> +       b       ftrace_common
> >> +SYM_CODE_END(ftrace_regs_caller)
> >> +#endif
> >> +
> >>   SYM_CODE_START(ftrace_common)
> >>          PTR_ADDI        a0, ra, -8      /* arg0: ip */
> >>          move            a1, t0          /* arg1: parent_ip */
> >> --
> >> 2.36.0
> >>
> >>
>
>