From: Aditya Bodkhe Date: Tue, 16 Sep 2025 04:40:34 +0000 (+0530) Subject: powerpc/ftrace: support CONFIG_FUNCTION_GRAPH_RETVAL X-Git-Tag: v6.18-rc1~206^2~11 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=d733f18a6da6fb719450d5122162556d785ed580;p=thirdparty%2Flinux.git powerpc/ftrace: support CONFIG_FUNCTION_GRAPH_RETVAL commit a1be9ccc57f0 ("function_graph: Support recording and printing the return value of function") introduced support for function graph return value tracing. Additionally, commit a3ed4157b7d8 ("fgraph: Replace fgraph_ret_regs with ftrace_regs") further refactored and optimized the implementation, making `struct fgraph_ret_regs` unnecessary. This patch enables the above modifications for powerpc all, ensuring that function graph return value tracing is available on this architecture. In this patch we have redefined two functions: - 'ftrace_regs_get_return_value()' - the existing implementation on ppc returns -ve of return value based on some conditions not relevant to our patch. - 'ftrace_regs_get_frame_pointer()' - always returns 0 in current code . We also allocate stack space to equivalent of 'SWITCH_FRAME_SIZE', allowing us to directly use predefined offsets like 'GPR3' and 'GPR4' this keeps code clean and consistent with already defined offsets . After this patch, v6.14+ kernel can also be built with FPROBE on powerpc but there are a few other build and runtime dependencies for FPROBE to work properly. The next patch addresses them. Tested-by: Venkat Rao Bagalkote Reviewed-by: Christophe Leroy Signed-off-by: Aditya Bodkhe Signed-off-by: Madhavan Srinivasan Link: https://patch.msgid.link/20250916044035.29033-1-adityab1@linux.ibm.com --- diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index ba9750c8e0cd8..449404d3932bf 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -246,6 +246,7 @@ config PPC select HAVE_FUNCTION_ARG_ACCESS_API select HAVE_FUNCTION_DESCRIPTORS if PPC64_ELF_ABI_V1 select HAVE_FUNCTION_ERROR_INJECTION + select HAVE_FUNCTION_GRAPH_FREGS select HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_TRACER if !COMPILE_TEST && (PPC64 || (PPC32 && CC_IS_GCC)) select HAVE_GCC_PLUGINS diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h index bd61a230b19d0..5984eaa75ce8d 100644 --- a/arch/powerpc/include/asm/ftrace.h +++ b/arch/powerpc/include/asm/ftrace.h @@ -50,6 +50,21 @@ static __always_inline struct pt_regs *arch_ftrace_get_regs(struct ftrace_regs * asm volatile("mfmsr %0" : "=r" ((_regs)->msr)); \ } while (0) +#undef ftrace_regs_get_return_value +static __always_inline unsigned long +ftrace_regs_get_return_value(const struct ftrace_regs *fregs) +{ + return arch_ftrace_regs(fregs)->regs.gpr[3]; +} +#define ftrace_regs_get_return_value ftrace_regs_get_return_value + +#undef ftrace_regs_get_frame_pointer +static __always_inline unsigned long +ftrace_regs_get_frame_pointer(const struct ftrace_regs *fregs) +{ + return arch_ftrace_regs(fregs)->regs.gpr[1]; +} + static __always_inline void ftrace_regs_set_instruction_pointer(struct ftrace_regs *fregs, unsigned long ip) diff --git a/arch/powerpc/kernel/trace/ftrace_entry.S b/arch/powerpc/kernel/trace/ftrace_entry.S index 3565c67fc6385..6599fe3c62347 100644 --- a/arch/powerpc/kernel/trace/ftrace_entry.S +++ b/arch/powerpc/kernel/trace/ftrace_entry.S @@ -409,23 +409,31 @@ EXPORT_SYMBOL(_mcount) _GLOBAL(return_to_handler) /* need to save return values */ #ifdef CONFIG_PPC64 - std r4, -32(r1) - std r3, -24(r1) + stdu r1, -SWITCH_FRAME_SIZE(r1) + std r4, GPR4(r1) + std r3, GPR3(r1) + /* Save previous stack pointer (r1) */ + addi r3, r1, SWITCH_FRAME_SIZE + std r3, GPR1(r1) /* save TOC */ - std r2, -16(r1) - std r31, -8(r1) + std r2, 24(r1) + std r31, 32(r1) mr r31, r1 - stdu r1, -112(r1) - + /* pass ftrace_regs/pt_regs to ftrace_return_to_handler */ + addi r3, r1, STACK_INT_FRAME_REGS /* * We might be called from a module. * Switch to our TOC to run inside the core kernel. */ LOAD_PACA_TOC() #else - stwu r1, -16(r1) - stw r3, 8(r1) - stw r4, 12(r1) + stwu r1, -SWITCH_FRAME_SIZE(r1) + stw r4, GPR4(r1) + stw r3, GPR3(r1) + addi r3, r1, SWITCH_FRAME_SIZE + stw r3, GPR1(r1) + /* pass ftrace_regs/pt_regs to ftrace_return_to_handler */ + addi r3, r1, STACK_INT_FRAME_REGS #endif bl ftrace_return_to_handler @@ -435,15 +443,15 @@ _GLOBAL(return_to_handler) mtlr r3 #ifdef CONFIG_PPC64 - ld r1, 0(r1) - ld r4, -32(r1) - ld r3, -24(r1) - ld r2, -16(r1) - ld r31, -8(r1) + ld r4, GPR4(r1) + ld r3, GPR3(r1) + ld r2, 24(r1) + ld r31, 32(r1) + ld r1, 0(r1) #else - lwz r3, 8(r1) - lwz r4, 12(r1) - addi r1, r1, 16 + lwz r3, GPR3(r1) + lwz r4, GPR4(r1) + addi r1, r1, SWITCH_FRAME_SIZE #endif /* Jump back to real return address */