Re: [PATCH v7 25/36] arm64: ftrace: Enable HAVE_FUNCTION_GRAPH_FREGS
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2024-02-15 16:08:50
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On Wed, 7 Feb 2024 00:12:06 +0900 "Masami Hiramatsu (Google)" [off-list ref] wrote:
quoted hunk ↗ jump to hunk
From: Masami Hiramatsu (Google) <mhiramat@kernel.org> Enable CONFIG_HAVE_FUNCTION_GRAPH_FREGS on arm64. Note that this depends on HAVE_DYNAMIC_FTRACE_WITH_ARGS which is enabled if the compiler supports "-fpatchable-function-entry=2". If not, it continue to use ftrace_ret_regs. Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> --- Changes in v3: - Newly added. --- arch/arm64/Kconfig | 2 ++ arch/arm64/include/asm/ftrace.h | 6 ++++++ arch/arm64/kernel/entry-ftrace.S | 28 ++++++++++++++++++++++++++++ 3 files changed, 36 insertions(+)diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index aa7c1d435139..34becd41ae66 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig@@ -194,6 +194,8 @@ config ARM64 select HAVE_DYNAMIC_FTRACE select HAVE_DYNAMIC_FTRACE_WITH_ARGS \ if $(cc-option,-fpatchable-function-entry=2) + select HAVE_FUNCTION_GRAPH_FREGS \ + if HAVE_DYNAMIC_FTRACE_WITH_ARGS select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS \ if DYNAMIC_FTRACE_WITH_ARGS && DYNAMIC_FTRACE_WITH_CALL_OPS select HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS \diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h index ab158196480c..efd5dbf74dd6 100644 --- a/arch/arm64/include/asm/ftrace.h +++ b/arch/arm64/include/asm/ftrace.h@@ -131,6 +131,12 @@ ftrace_regs_set_return_value(struct ftrace_regs *fregs, fregs->regs[0] = ret; } +static __always_inline unsigned long +ftrace_regs_get_frame_pointer(struct ftrace_regs *fregs) +{ + return fregs->fp; +} + static __always_inline void ftrace_override_function_with_return(struct ftrace_regs *fregs) {diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S index f0c16640ef21..d87ccdb9e678 100644 --- a/arch/arm64/kernel/entry-ftrace.S +++ b/arch/arm64/kernel/entry-ftrace.S@@ -328,6 +328,33 @@ SYM_FUNC_END(ftrace_stub_graph) * Run ftrace_return_to_handler() before going back to parent. * @fp is checked against the value passed by ftrace_graph_caller(). */ +#ifdef CONFIG_HAVE_FUNCTION_GRAPH_FREGS +SYM_CODE_START(return_to_handler) + /* save ftrace_regs except for PC */ + sub sp, sp, #FREGS_SIZE + stp x0, x1, [sp, #FREGS_X0] + stp x2, x3, [sp, #FREGS_X2] + stp x4, x5, [sp, #FREGS_X4] + stp x6, x7, [sp, #FREGS_X6] + str x8, [sp, #FREGS_X8] + str x29, [sp, #FREGS_FP] + str x9, [sp, #FREGS_LR] + str x10, [sp, #FREGS_SP]
Here too. The above is just garbage. Let's not fill in garbarge registers. The above is useless on return of a function. Heck, adding zeros is better than this. But really, we need to have ftrace regs to have some kind of flag that can state what it holds. Right now I see three states: 1 - holds all regs and pt_regs can be retrieved 2 - only holds function entry regs (parameters and stack) 3 - only holds function exit regs (return value and stack) Don't save anything else unless needed. -- Steve
quoted hunk ↗ jump to hunk
+ + mov x0, sp + bl ftrace_return_to_handler // addr = ftrace_return_to_hander(fregs); + mov x30, x0 // restore the original return address + + /* restore return value regs */ + ldp x0, x1, [sp, #FREGS_X0] + ldp x2, x3, [sp, #FREGS_X2] + ldp x4, x5, [sp, #FREGS_X4] + ldp x6, x7, [sp, #FREGS_X6] + add sp, sp, #FREGS_SIZE + + ret +SYM_CODE_END(return_to_handler) +#else /* !CONFIG_HAVE_FUNCTION_GRAPH_FREGS */ SYM_CODE_START(return_to_handler) /* save return value regs */ sub sp, sp, #FGRET_REGS_SIZE@@ -350,4 +377,5 @@ SYM_CODE_START(return_to_handler) ret SYM_CODE_END(return_to_handler) +#endif /* CONFIG_HAVE_FUNCTION_GRAPH_FREGS */ #endif /* CONFIG_FUNCTION_GRAPH_TRACER */