On Wed, Feb 11, 2015 at 10:55:52PM +0100, Denys Vlasenko wrote: > 64-bit code was using six stack slots less by not saving/restoring > registers which are callee-preserved according to C ABI, > and not allocating space for them. > Only when syscall needed a complete "struct pt_regs", > the complete area was allocated and filled in. > As an additional twist, on interrupt entry a "slightly less truncated pt_regs" > trick is used, to make nested interrupt stacks easier to unwind. > > This proved to be a source of significant obfuscation and subtle bugs. > For example, stub_fork had to pop the return address, > extend the struct, save registers, and push return address back. Ugly. > ia32_ptregs_common pops return address and "returns" via jmp insn, > throwing a wrench into CPU return stack cache. > > This patch changes code to always allocate a complete "struct pt_regs". > The saving of registers is still done lazily. > > "Partial pt_regs" trick on interrupt stack is retained. > > Macros which manipulate "struct pt_regs" on stack are reworked: > ALLOC_PT_GPREGS_ON_STACK allocates the structure. > SAVE_C_REGS saves to it those registers which are clobbered by C code. > SAVE_EXTRA_REGS saves to it all other registers. > Corresponding RESTORE_* and REMOVE_PT_GPREGS_FROM_STACK macros reverse it. > > ia32_ptregs_common, stub_fork and friends lost their ugly dance with > return pointer. > > LOAD_ARGS32 in ia32entry.S now uses symbolic stack offsets > instead of magic numbers. > > error_entry and save_paranoid now use SAVE_C_REGS + SAVE_EXTRA_REGS > instead of having it open-coded yet again. > > Patch was run-tested: 64-bit executables, 32-bit executables, > strace works. > Timing tests did not show measurable difference in 32-bit > and 64-bit syscalls. > > Signed-off-by: Denys Vlasenko <dvlas...@redhat.com> > CC: Linus Torvalds <torva...@linux-foundation.org> > CC: Oleg Nesterov <o...@redhat.com> > CC: Borislav Petkov <b...@alien8.de> > CC: "H. Peter Anvin" <h...@zytor.com> > CC: Andy Lutomirski <l...@amacapital.net> > CC: Frederic Weisbecker <fweis...@gmail.com> > CC: X86 ML <x...@kernel.org> > CC: Alexei Starovoitov <a...@plumgrid.com> > CC: Will Drewry <w...@chromium.org> > CC: Kees Cook <keesc...@chromium.org> > CC: linux-kernel@vger.kernel.org > --- > arch/x86/ia32/ia32entry.S | 47 +++---- > arch/x86/include/asm/calling.h | 222 > ++++++++++++++++----------------- > arch/x86/include/asm/irqflags.h | 4 +- > arch/x86/include/uapi/asm/ptrace-abi.h | 1 - > arch/x86/kernel/entry_64.S | 192 +++++++++++-----------------
You'd need to redo that patch against latest upstream because of changes it is missing: Andy's branch x86/entry should have them too: http://git.kernel.org/cgit/linux/kernel/git/luto/linux.git arch/x86/kernel/entry_64.S: Assembler messages: arch/x86/kernel/entry_64.S:760: Error: no such instruction: `restore_args 1,8,1' make[2]: *** [arch/x86/kernel/entry_64.o] Error 1 make[1]: *** [arch/x86/kernel] Error 2 make[1]: *** Waiting for unfinished jobs.... make: *** [arch/x86] Error 2 make: *** Waiting for unfinished jobs.... -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
