Hi,
Gentry ping.
I think this should be an important fix because if a fprobe handler without
FTRACE_OPS_FL_SAVE_REGS tries to access any register via ftrace_regs, that
will get a wrong value.
Thank you,
On Mon, 2 Oct 2023 21:50:34 +0900
"Masami Hiramatsu (Google)" <mhira...@kernel.org> wrote:
> From: Masami Hiramatsu (Google) <mhira...@kernel.org>
>
> Since ftrace_func_t requires to pass 'struct ftrace_regs *' as the 4th
> argument even if FTRACE_OPS_FL_SAVE_REGS is not set, ftrace_caller must
> pass 'struct ftrace_regs *', which is a partial pt_regs, on the stack
> to the ftrace_func_t functions, so that the ftrace_func_t functions can
> access some partial registers.
>
> Fix to allocate 'struct ftrace_regs' (which has the same size of 'struct
> pt_regs') on the stack and save partial (argument) registers on it
> instead of reduced size custom data structure.
>
> Fixes: afc76b8b8011 ("riscv: Using PATCHABLE_FUNCTION_ENTRY instead of
> MCOUNT")
> Signed-off-by: Masami Hiramatsu (Google) <mhira...@kernel.org>
> ---
> arch/riscv/kernel/mcount-dyn.S | 65
> +++++++++++++++++-----------------------
> 1 file changed, 28 insertions(+), 37 deletions(-)
>
> diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S
> index 669b8697aa38..84963680eff4 100644
> --- a/arch/riscv/kernel/mcount-dyn.S
> +++ b/arch/riscv/kernel/mcount-dyn.S
> @@ -14,46 +14,37 @@
> .text
>
> #define FENTRY_RA_OFFSET 8
> -#define ABI_SIZE_ON_STACK 80
> -#define ABI_A0 0
> -#define ABI_A1 8
> -#define ABI_A2 16
> -#define ABI_A3 24
> -#define ABI_A4 32
> -#define ABI_A5 40
> -#define ABI_A6 48
> -#define ABI_A7 56
> -#define ABI_T0 64
> -#define ABI_RA 72
>
> .macro SAVE_ABI
> - addi sp, sp, -ABI_SIZE_ON_STACK
> -
> - REG_S a0, ABI_A0(sp)
> - REG_S a1, ABI_A1(sp)
> - REG_S a2, ABI_A2(sp)
> - REG_S a3, ABI_A3(sp)
> - REG_S a4, ABI_A4(sp)
> - REG_S a5, ABI_A5(sp)
> - REG_S a6, ABI_A6(sp)
> - REG_S a7, ABI_A7(sp)
> - REG_S t0, ABI_T0(sp)
> - REG_S ra, ABI_RA(sp)
> + addi sp, sp, -PT_SIZE_ON_STACK
> +
> + /* Save t0 as epc for ftrace_regs_get_instruction_pointer() */
> + REG_S t0, PT_EPC(sp)
> + REG_S a0, PT_A0(sp)
> + REG_S a1, PT_A1(sp)
> + REG_S a2, PT_A2(sp)
> + REG_S a3, PT_A3(sp)
> + REG_S a4, PT_A4(sp)
> + REG_S a5, PT_A5(sp)
> + REG_S a6, PT_A6(sp)
> + REG_S a7, PT_A7(sp)
> + REG_S t0, PT_T0(sp)
> + REG_S ra, PT_RA(sp)
> .endm
>
> .macro RESTORE_ABI
> - REG_L a0, ABI_A0(sp)
> - REG_L a1, ABI_A1(sp)
> - REG_L a2, ABI_A2(sp)
> - REG_L a3, ABI_A3(sp)
> - REG_L a4, ABI_A4(sp)
> - REG_L a5, ABI_A5(sp)
> - REG_L a6, ABI_A6(sp)
> - REG_L a7, ABI_A7(sp)
> - REG_L t0, ABI_T0(sp)
> - REG_L ra, ABI_RA(sp)
> -
> - addi sp, sp, ABI_SIZE_ON_STACK
> + REG_L a0, PT_A0(sp)
> + REG_L a1, PT_A1(sp)
> + REG_L a2, PT_A2(sp)
> + REG_L a3, PT_A3(sp)
> + REG_L a4, PT_A4(sp)
> + REG_L a5, PT_A5(sp)
> + REG_L a6, PT_A6(sp)
> + REG_L a7, PT_A7(sp)
> + REG_L t0, PT_T0(sp)
> + REG_L ra, PT_RA(sp)
> +
> + addi sp, sp, PT_SIZE_ON_STACK
> .endm
>
> #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> @@ -96,8 +87,8 @@ ftrace_call:
> call ftrace_stub
>
> #ifdef CONFIG_FUNCTION_GRAPH_TRACER
> - addi a0, sp, ABI_RA
> - REG_L a1, ABI_T0(sp)
> + addi a0, sp, PT_RA
> + REG_L a1, PT_T0(sp)
> addi a1, a1, -FENTRY_RA_OFFSET
> #ifdef HAVE_FUNCTION_GRAPH_FP_TEST
> mv a2, s0
>
>
--
Masami Hiramatsu (Google) <mhira...@kernel.org>
