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ftrace: arm64: remove static ftrace 

The build test robot pointer out that there's a build failure when:

  CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS=y
  CONFIG_DYNAMIC_FTRACE_WITH_ARGS=n

... due to some mismatched ifdeffery, some of which checks
CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS, and some of which checks
CONFIG_DYNAMIC_FTRACE_WITH_ARGS, leading to some missing definitions expected
by the core code when CONFIG_DYNAMIC_FTRACE=n and consequently
CONFIG_DYNAMIC_FTRACE_WITH_ARGS=n.

There's really not much point in supporting CONFIG_DYNAMIC_FTRACE=n (AKA
static ftrace). All supported toolchains allow us to implement
DYNAMIC_FTRACE, distributions all prefer DYNAMIC_FTRACE, and both
powerpc and s390 removed support for static ftrace in commits:

  0c0c52306f ("powerpc: Only support DYNAMIC_FTRACE not static")
  5d6a016349 ("s390/ftrace: enforce DYNAMIC_FTRACE if FUNCTION_TRACER is selected")

... and according to Steven, static ftrace is only supported on x86 to
allow testing that the core code still functions in this configuration.

Given that, let's simplify matters by removing arm64's support for
static ftrace. This avoids the problem originally reported, and leaves
us with less code to maintain.

Fixes: 26299b3f6b ("ftrace: arm64: move from REGS to ARGS")
Link: https://lore.kernel.org/r/202211212249.livTPi3Y-lkp@intel.com
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20221122163624.1225912-1-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Mark Rutland 2022-11-22 16:36:24 +00:00 committed by Will Deacon
parent 26299b3f6b
commit cfce092dae
3 changed files with 1 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/arm64/Kconfig
View File

@ -117,6 +117,7 @@ config ARM64
select CPU_PM if (SUSPEND || CPU_IDLE)
select CRC32
select DCACHE_WORD_ACCESS
select DYNAMIC_FTRACE if FUNCTION_TRACER
select DMA_DIRECT_REMAP
select EDAC_SUPPORT
select FRAME_POINTER

39
arch/arm64/kernel/entry-ftrace.S
View File

@ -170,44 +170,6 @@ SYM_CODE_END(ftrace_caller)
add \reg, \reg, #8
.endm
#ifndef CONFIG_DYNAMIC_FTRACE
/*
* void _mcount(unsigned long return_address)
* @return_address: return address to instrumented function
*
* This function makes calls, if enabled, to:
* - tracer function to probe instrumented function's entry,
* - ftrace_graph_caller to set up an exit hook
*/
SYM_FUNC_START(_mcount)
mcount_enter
ldr_l x2, ftrace_trace_function
adr x0, ftrace_stub
cmp x0, x2 // if (ftrace_trace_function
b.eq skip_ftrace_call // != ftrace_stub) {
mcount_get_pc x0 // function's pc
mcount_get_lr x1 // function's lr (= parent's pc)
blr x2 // (*ftrace_trace_function)(pc, lr);
skip_ftrace_call: // }
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
ldr_l x2, ftrace_graph_return
cmp x0, x2 // if ((ftrace_graph_return
b.ne ftrace_graph_caller // != ftrace_stub)
ldr_l x2, ftrace_graph_entry // || (ftrace_graph_entry
adr_l x0, ftrace_graph_entry_stub // != ftrace_graph_entry_stub))
cmp x0, x2
b.ne ftrace_graph_caller // ftrace_graph_caller();
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
mcount_exit
SYM_FUNC_END(_mcount)
EXPORT_SYMBOL(_mcount)
NOKPROBE(_mcount)
#else /* CONFIG_DYNAMIC_FTRACE */
/*
* _mcount() is used to build the kernel with -pg option, but all the branch
* instructions to _mcount() are replaced to NOP initially at kernel start up,
@ -247,7 +209,6 @@ SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL) // ftrace_graph_caller();
mcount_exit
SYM_FUNC_END(ftrace_caller)
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/*

5
arch/arm64/kernel/ftrace.c
View File

@ -60,7 +60,6 @@ int ftrace_regs_query_register_offset(const char *name)
}
#endif
#ifdef CONFIG_DYNAMIC_FTRACE
/*
* Replace a single instruction, which may be a branch or NOP.
* If @validate == true, a replaced instruction is checked against 'old'.
@ -268,7 +267,6 @@ void arch_ftrace_update_code(int command)
command |= FTRACE_MAY_SLEEP;
ftrace_modify_all_code(command);
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/*
@ -299,8 +297,6 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
}
}
#ifdef CONFIG_DYNAMIC_FTRACE
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct ftrace_regs *fregs)
@ -338,5 +334,4 @@ int ftrace_disable_ftrace_graph_caller(void)
return ftrace_modify_graph_caller(false);
}
#endif /* CONFIG_DYNAMIC_FTRACE_WITH_ARGS */
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */