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Commit 76a5eaa3 authored by Diana Craciun's avatar Diana Craciun Committed by Michael Ellerman
Browse files

powerpc/fsl: Add infrastructure to fixup branch predictor flush 



In order to protect against speculation attacks (Spectre
variant 2) on NXP PowerPC platforms, the branch predictor
should be flushed when the privillege level is changed.
This patch is adding the infrastructure to fixup at runtime
the code sections that are performing the branch predictor flush
depending on a boot arg parameter which is added later in a
separate patch.

Signed-off-by: default avatarDiana Craciun <diana.craciun@nxp.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent f242e0ac

arch/powerpc/include/asm/feature-fixups.h

+12 −0
Original line number Diff line number Diff line
@@ -221,6 +221,17 @@ label##3: \ 
	FTR_ENTRY_OFFSET 953b-954b;			\

	.popsection;



#define START_BTB_FLUSH_SECTION			\

955:							\



#define END_BTB_FLUSH_SECTION			\

956:							\

	.pushsection __btb_flush_fixup,"a";	\

	.align 2;							\

957:						\

	FTR_ENTRY_OFFSET 955b-957b;			\

	FTR_ENTRY_OFFSET 956b-957b;			\

	.popsection;



#ifndef __ASSEMBLY__

#include <linux/types.h>
@@ -230,6 +241,7 @@ extern long __start___stf_entry_barrier_fixup, __stop___stf_entry_barrier_fixup; 
extern long __start___stf_exit_barrier_fixup, __stop___stf_exit_barrier_fixup;

extern long __start___rfi_flush_fixup, __stop___rfi_flush_fixup;

extern long __start___barrier_nospec_fixup, __stop___barrier_nospec_fixup;

extern long __start__btb_flush_fixup, __stop__btb_flush_fixup;



void apply_feature_fixups(void);

void setup_feature_keys(void);

arch/powerpc/include/asm/setup.h

+2 −0
Original line number Diff line number Diff line
@@ -67,6 +67,8 @@ void do_barrier_nospec_fixups_range(bool enable, void *start, void *end); 
static inline void do_barrier_nospec_fixups_range(bool enable, void *start, void *end) { };

#endif



void do_btb_flush_fixups(void);



#endif /* !__ASSEMBLY__ */



#endif	/* _ASM_POWERPC_SETUP_H */

arch/powerpc/kernel/vmlinux.lds.S

+8 −0
Original line number Diff line number Diff line
@@ -170,6 +170,14 @@ SECTIONS 
	}

#endif /* CONFIG_PPC_BARRIER_NOSPEC */



#ifdef CONFIG_PPC_FSL_BOOK3E

	. = ALIGN(8);

	__spec_btb_flush_fixup : AT(ADDR(__spec_btb_flush_fixup) - LOAD_OFFSET) {

		__start__btb_flush_fixup = .;

		*(__btb_flush_fixup)

		__stop__btb_flush_fixup = .;

	}

#endif

	EXCEPTION_TABLE(0)



	NOTES :kernel :notes

arch/powerpc/lib/feature-fixups.c

+23 −0
Original line number Diff line number Diff line
@@ -347,6 +347,29 @@ void do_barrier_nospec_fixups_range(bool enable, void *fixup_start, void *fixup_ 


	printk(KERN_DEBUG "barrier-nospec: patched %d locations\n", i);

}



static void patch_btb_flush_section(long *curr)

{

	unsigned int *start, *end;



	start = (void *)curr + *curr;

	end = (void *)curr + *(curr + 1);

	for (; start < end; start++) {

		pr_devel("patching dest %lx\n", (unsigned long)start);

		patch_instruction(start, PPC_INST_NOP);

	}

}



void do_btb_flush_fixups(void)

{

	long *start, *end;



	start = PTRRELOC(&__start__btb_flush_fixup);

	end = PTRRELOC(&__stop__btb_flush_fixup);



	for (; start < end; start += 2)

		patch_btb_flush_section(start);

}

#endif /* CONFIG_PPC_FSL_BOOK3E */



void do_lwsync_fixups(unsigned long value, void *fixup_start, void *fixup_end)