On Wed, Sep 2, 2020 at 7:31 PM Arvind Sankar <[email protected]> wrote: > > When CONFIG_RETPOLINE is disabled, Clang uses a jump table for the > switch statement in cmdline_find_option (jump tables are disabled when > CONFIG_RETPOLINE is enabled). This function is called very early in boot > from sme_enable() if CONFIG_AMD_MEM_ENCRYPT is enabled. At this time,
Hi Arvind, sorry I missed this when you first sent it. I'm going through and mass deleting my inbox (email bankruptcy) but noticed this. I couldn't reproduce jump tables in cmdline_find_option with CONFIG_RETPOLINE disabled but CONFIG_AMD_MEM_ENCRYPT on today's linux-next. Can you please confirm that this is still an issue? I will reread the disassembly, but it looks like a bunch of cmp/test+jumps. > the kernel is still executing out of the identity mapping, but the jump > table will contain virtual addresses. > > Fix this by disabling jump tables for cmdline.c when AMD_MEM_ENCRYPT is > enabled. > > Signed-off-by: Arvind Sankar <[email protected]> > --- > arch/x86/lib/Makefile | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile > index d46fff11f06f..aa067859a70b 100644 > --- a/arch/x86/lib/Makefile > +++ b/arch/x86/lib/Makefile > @@ -24,7 +24,7 @@ ifdef CONFIG_FUNCTION_TRACER > CFLAGS_REMOVE_cmdline.o = -pg > endif > > -CFLAGS_cmdline.o := -fno-stack-protector > +CFLAGS_cmdline.o := -fno-stack-protector -fno-jump-tables > endif > > inat_tables_script = $(srctree)/arch/x86/tools/gen-insn-attr-x86.awk > -- > 2.26.2 > > -- > You received this message because you are subscribed to the Google Groups > "Clang Built Linux" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/clang-built-linux/20200903023056.3914690-1-nivedita%40alum.mit.edu. -- Thanks, ~Nick Desaulniers
