3.2.101-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: David Woodhouse <d...@amazon.co.uk> commit 2641f08bb7fc63a636a2b18173221d7040a3512e upstream. Convert indirect jumps in core 32/64bit entry assembler code to use non-speculative sequences when CONFIG_RETPOLINE is enabled. Don't use CALL_NOSPEC in entry_SYSCALL_64_fastpath because the return address after the 'call' instruction must be *precisely* at the .Lentry_SYSCALL_64_after_fastpath label for stub_ptregs_64 to work, and the use of alternatives will mess that up unless we play horrid games to prepend with NOPs and make the variants the same length. It's not worth it; in the case where we ALTERNATIVE out the retpoline, the first instruction at __x86.indirect_thunk.rax is going to be a bare jmp *%rax anyway. Signed-off-by: David Woodhouse <d...@amazon.co.uk> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Acked-by: Ingo Molnar <mi...@kernel.org> Acked-by: Arjan van de Ven <ar...@linux.intel.com> Cc: gno...@lxorguk.ukuu.org.uk Cc: Rik van Riel <r...@redhat.com> Cc: Andi Kleen <a...@linux.intel.com> Cc: Josh Poimboeuf <jpoim...@redhat.com> Cc: thomas.lenda...@amd.com Cc: Peter Zijlstra <pet...@infradead.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Jiri Kosina <ji...@kernel.org> Cc: Andy Lutomirski <l...@amacapital.net> Cc: Dave Hansen <dave.han...@intel.com> Cc: Kees Cook <keesc...@google.com> Cc: Tim Chen <tim.c.c...@linux.intel.com> Cc: Greg Kroah-Hartman <gre...@linux-foundation.org> Cc: Paul Turner <p...@google.com> Link: https://lkml.kernel.org/r/1515707194-20531-7-git-send-email-d...@amazon.co.uk Signed-off-by: David Woodhouse <d...@amazon.co.uk> Signed-off-by: Razvan Ghitulete <r...@amazon.de> [bwh: Backported to 3.2: adjust filenames, context] Signed-off-by: Ben Hutchings <b...@decadent.org.uk> --- --- a/arch/x86/kernel/entry_32.S +++ b/arch/x86/kernel/entry_32.S @@ -55,6 +55,7 @@ #include <asm/irq_vectors.h> #include <asm/cpufeature.h> #include <asm/alternative-asm.h> +#include <asm/nospec-branch.h> /* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this. */ #include <linux/elf-em.h> @@ -1017,7 +1018,7 @@ ENTRY(kernel_thread_helper) pushl $0 # fake return address for unwinder CFI_STARTPROC movl %edi,%eax - call *%esi + CALL_NOSPEC %esi call do_exit ud2 # padding for call trace CFI_ENDPROC @@ -1274,7 +1275,7 @@ error_code: movl %ecx, %es TRACE_IRQS_OFF movl %esp,%eax # pt_regs pointer - call *%edi + CALL_NOSPEC %edi jmp ret_from_exception CFI_ENDPROC END(page_fault) --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -59,6 +59,7 @@ #include <asm/alternative-asm.h> #include <asm/cpufeature.h> #include <asm/kaiser.h> +#include <asm/nospec-branch.h> /* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this. */ #include <linux/elf-em.h> @@ -519,7 +520,12 @@ system_call_fastpath: cmpq $__NR_syscall_max,%rax ja badsys movq %r10,%rcx +#ifdef CONFIG_RETPOLINE + movq sys_call_table(, %rax, 8), %rax + call __x86_indirect_thunk_rax +#else call *sys_call_table(,%rax,8) # XXX: rip relative +#endif movq %rax,RAX-ARGOFFSET(%rsp) /* * Syscall return path ending with SYSRET (fast path) @@ -643,7 +649,12 @@ tracesys: cmpq $__NR_syscall_max,%rax ja int_ret_from_sys_call /* RAX(%rsp) set to -ENOSYS above */ movq %r10,%rcx /* fixup for C */ +#ifdef CONFIG_RETPOLINE + movq sys_call_table(, %rax, 8), %rax + call __x86_indirect_thunk_rax +#else call *sys_call_table(,%rax,8) +#endif movq %rax,RAX-ARGOFFSET(%rsp) /* Use IRET because user could have changed frame */ @@ -1219,7 +1230,7 @@ ENTRY(kernel_thread_helper) * Here we are in the child and the registers are set as they were * at kernel_thread() invocation in the parent. */ - call *%rsi + CALL_NOSPEC %rsi # exit mov %eax, %edi call do_exit
