Messages in this thread Patch in this message | | | Date | Mon, 2 May 2022 11:15:47 -0700 | From | Josh Poimboeuf <> | Subject | Re: [PATCH] objtool: Fix SLS checks |
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On Sat, Apr 30, 2022 at 12:50:02PM +0200, Peter Zijlstra wrote: > > Fix the SLS validation; not having a next instruction is also a fail > when the next instruction should be INSN_TRAP. > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > --- > tools/objtool/check.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/tools/objtool/check.c b/tools/objtool/check.c > index 3f6785415894..3354101ffe34 100644 > --- a/tools/objtool/check.c > +++ b/tools/objtool/check.c > @@ -3380,7 +3380,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, > > case INSN_RETURN: > if (sls && !insn->retpoline_safe && > - next_insn && next_insn->type != INSN_TRAP) { > + (!next_insn || (next_insn && next_insn->type != INSN_TRAP))) { > WARN_FUNC("missing int3 after ret", > insn->sec, insn->offset); > } > @@ -3428,7 +3428,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, > > case INSN_JUMP_DYNAMIC: > if (sls && !insn->retpoline_safe && > - next_insn && next_insn->type != INSN_TRAP) { > + (!next_insn || (next_insn && next_insn->type != INSN_TRAP))) { > WARN_FUNC("missing int3 after indirect jump", > insn->sec, insn->offset); > }
My SLS rewrite in tip/objtool/core already fixed this, FWIW. But this could be good for -urgent.
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Here's another SLS improvement I mentioned to you the other day, do you agree we should do this as well?
From: Josh Poimboeuf <jpoimboe@redhat.com> Subject: [PATCH] x86/speculation: Mitigate SLS for JMP_NOSPEC with retpolines disabled
Having disabled retpolines doesn't necessarily mean the user doesn't care about straight-line speculation. For example, retpolines are disabled when eIBRS is used.
If CONFIG_SLS is enabled, properly mitigate SLS for JMP_NOSPEC for the retpolines disabled cases.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> --- arch/x86/include/asm/nospec-branch.h | 13 ++++++++++--- tools/objtool/check.c | 3 --- 2 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index acbaeaf83b61..0648746bf60b 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -75,6 +75,13 @@ .popsection .endm +.macro INDIRECT_JMP reg + jmp *%\reg +#ifdef CONFIG_SLS + int3 +#endif +.endm + /* * JMP_NOSPEC and CALL_NOSPEC macros can be used instead of a simple * indirect jmp/call which may be susceptible to the Spectre variant 2 @@ -82,11 +89,11 @@ */ .macro JMP_NOSPEC reg:req #ifdef CONFIG_RETPOLINE - ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), \ + ALTERNATIVE_2 __stringify(ANNOTATE_RETPOLINE_SAFE; INDIRECT_JMP \reg), \ __stringify(jmp __x86_indirect_thunk_\reg), X86_FEATURE_RETPOLINE, \ - __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; jmp *%\reg), X86_FEATURE_RETPOLINE_LFENCE + __stringify(lfence; ANNOTATE_RETPOLINE_SAFE; INDIRECT_JMP \reg), X86_FEATURE_RETPOLINE_LFENCE #else - jmp *%\reg + INDIRECT_JMP \reg #endif .endm diff --git a/tools/objtool/check.c b/tools/objtool/check.c index e7983c3e2408..3cf3ad0b5db5 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -3842,9 +3842,6 @@ static int validate_sls(struct objtool_file *file) for_each_insn(file, insn) { next_insn = next_insn_same_sec(file, insn); - if (insn->retpoline_safe) - continue; - switch (insn->type) { case INSN_RETURN: if (!next_insn || next_insn->type != INSN_TRAP) { -- 2.34.1
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