Messages in this thread | | | Date | Mon, 28 Oct 2019 16:25:26 +0000 | From | Will Deacon <> | Subject | Re: [PATCH v4 13/16] arm/ftrace: Use __patch_text_real() |
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Hi Peter,
On Fri, Oct 18, 2019 at 09:35:38AM +0200, Peter Zijlstra wrote: > Instead of flipping text protection, use the patch_text infrastructure > that uses a fixmap alias where required. > > This removes the last user of set_all_modules_text_*(). > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Cc: ard.biesheuvel@linaro.org > Cc: rabin@rab.in > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: Will Deacon <will@kernel.org> > Cc: james.morse@arm.com > --- > arch/arm/kernel/ftrace.c | 16 ++++++++-------- > 1 file changed, 8 insertions(+), 8 deletions(-) > > --- 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} */ > @@ -31,13 +32,15 @@ > > #ifdef CONFIG_DYNAMIC_FTRACE > > +static int patch_text_remap = 0; > + > static int __ftrace_modify_code(void *data) > { > int *command = data; > > - set_kernel_text_rw(); > + patch_text_remap++; > ftrace_modify_all_code(*command); > - set_kernel_text_ro(); > + patch_text_remap--; > > return 0; > } > @@ -59,13 +62,13 @@ static unsigned long adjust_address(stru > > int ftrace_arch_code_modify_prepare(void) > { > - set_all_modules_text_rw(); > + patch_text_remap++; > return 0; > } > > int ftrace_arch_code_modify_post_process(void) > { > - set_all_modules_text_ro(); > + patch_text_remap--; > /* Make sure any TLB misses during machine stop are cleared. */ > flush_tlb_all(); > return 0; > @@ -97,10 +100,7 @@ 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, patch_text_remap);
Why can't you just pass 'true' for patch_text_remap? AFAICT, the only time you want to pass false is during early boot when the text is assumedly still writable without the fixmap.
Will
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