From: Diana Craciun diana.craciun@nxp.com
commit 76a5eaa38b15dda92cd6964248c39b5a6f3a4e9d upstream.
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: Diana Craciun diana.craciun@nxp.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/powerpc/include/asm/feature-fixups.h | 12 ++++++++++++ arch/powerpc/include/asm/setup.h | 2 ++ arch/powerpc/kernel/vmlinux.lds.S | 8 ++++++++ arch/powerpc/lib/feature-fixups.c | 23 +++++++++++++++++++++++ 4 files changed, 45 insertions(+)
--- a/arch/powerpc/include/asm/feature-fixups.h +++ b/arch/powerpc/include/asm/feature-fixups.h @@ -216,6 +216,17 @@ 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__
@@ -224,6 +235,7 @@ extern long __start___stf_entry_barrier_ 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;
#endif
--- a/arch/powerpc/include/asm/setup.h +++ b/arch/powerpc/include/asm/setup.h @@ -53,6 +53,8 @@ void do_barrier_nospec_fixups_range(bool 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 */ --- a/arch/powerpc/kernel/vmlinux.lds.S +++ b/arch/powerpc/kernel/vmlinux.lds.S @@ -104,6 +104,14 @@ 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 --- a/arch/powerpc/lib/feature-fixups.c +++ b/arch/powerpc/lib/feature-fixups.c @@ -344,6 +344,29 @@ void do_barrier_nospec_fixups_range(bool
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)