Re: [PATCH -v5 13/17] arm/ftrace: Use __patch_text_real()

Peter Zijlstra
2019-11-11T17:20:33Z

On Mon, Nov 11, 2019 at 04:47:03PM +0000, Will Deacon wrote:

> I'd still prefer to pass 'true' unconditionally here, since I don't think
> this is a hot path.

If you can give me a Tested-by, I'll replace it with the below... :-)

--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -22,6 +22,7 @@
#include <asm/ftrace.h>
#include <asm/insn.h>
#include <asm/set_memory.h>
+#include <asm/patch.h>

#ifdef CONFIG_THUMB2_KERNEL
#define NOP 0xf85deb04 /* pop.w {lr} */
@@ -35,9 +36,7 @@ static int __ftrace_modify_code(void *da
{
int *command = data;

- set_kernel_text_rw();
ftrace_modify_all_code(*command);
- set_kernel_text_ro();

return 0;
}
@@ -59,13 +58,11 @@ static unsigned long adjust_address(stru

int ftrace_arch_code_modify_prepare(void)
{
- set_all_modules_text_rw();
return 0;
}

int ftrace_arch_code_modify_post_process(void)
{
- set_all_modules_text_ro();
/* Make sure any TLB misses during machine stop are cleared. */
flush_tlb_all();
return 0;
@@ -97,10 +94,7 @@ static int ftrace_modify_code(unsigned l
return -EINVAL;
}

- if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
- return -EPERM;
-
- flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
+ __patch_text_real((void *)pc, new, true);

return 0;
}