Re: [PATCH v16 04/18] function_graph: Replace fgraph_ret_regs with ftrace_regs
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Date: 2024-10-15 23:33:22
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On Tue, 15 Oct 2024 20:39:06 +0200 Heiko Carstens [off-list ref] wrote:
On Tue, Oct 15, 2024 at 10:29:17AM +0900, Masami Hiramatsu (Google) wrote:quoted
From: Masami Hiramatsu (Google) <mhiramat@kernel.org> Use ftrace_regs instead of fgraph_ret_regs for tracing return value on function_graph tracer because of simplifying the callback interface. The CONFIG_HAVE_FUNCTION_GRAPH_RETVAL is also replaced by CONFIG_HAVE_FUNCTION_GRAPH_FREGS. Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>...quoted
diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S index 7e267ef63a7f..a9ca56ea0858 100644 --- a/arch/s390/kernel/mcount.S +++ b/arch/s390/kernel/mcount.S@@ -134,14 +134,15 @@ SYM_CODE_END(ftrace_common) SYM_FUNC_START(return_to_handler) stmg %r2,%r5,32(%r15) lgr %r1,%r15 - aghi %r15,-(STACK_FRAME_OVERHEAD+__FGRAPH_RET_SIZE) + aghi %r15,-(STACK_FRAME_OVERHEAD+STACK_FRAME_SIZE_FREGS) stg %r1,__SF_BACKCHAIN(%r15) - la %r3,STACK_FRAME_OVERHEAD(%r15) - stg %r1,__FGRAPH_RET_FP(%r3) - stg %r2,__FGRAPH_RET_GPR2(%r3) - lgr %r2,%r3 + la %r4,STACK_FRAME_OVERHEAD(%r15) + stg %r2,__PT_R2(%r4) + stg %r3,__PT_R3(%r4) + stg %r1,__PT_R15(%r4) + lgr %r2,%r4 brasl %r14,ftrace_return_to_handler - aghi %r15,STACK_FRAME_OVERHEAD+__FGRAPH_RET_SIZE + aghi %r15,STACK_FRAME_SIZE_FREGS lgr %r14,%r2 lmg %r2,%r5,32(%r15) BR_EX %r14Why didn't you simply merge the addon patch which I provided, and which I tested? https://lore.kernel.org/all/20240916121656.20933-B-hca@linux.ibm.com (local) That would make things much simpler... e.g. your new patch is also writing r3 to fregs, why? The stackframe allocation is also wrong. I didn't try, but I guess the above code would crash instantly.
I thought it is better to focus on replacing fgraph_ret_regs with ftrace_regs in this patch, but if it is wrong and I should remove stack_frame, let me fix that. Thank you, -- Masami Hiramatsu (Google) [off-list ref]