On Wed, Jul 17, 2019 at 05:02:06PM -0700, Vaibhav Rustagi wrote: > From: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > > Implementing memcpy and memset in terms of __builtin_memcpy and > __builtin_memset is problematic. > > GCC at -O2 will replace calls to the builtins with calls to memcpy and > memset (but will generate an inline implementation at -Os). Clang will > replace the builtins with these calls regardless of optimization level. > > $ llvm-objdump -dr arch/x86/purgatory/string.o | tail > > 0000000000000339 memcpy: > 339: 48 b8 00 00 00 00 00 00 00 00 movabsq $0, %rax > 000000000000033b: R_X86_64_64 memcpy > 343: ff e0 jmpq *%rax > > 0000000000000345 memset: > 345: 48 b8 00 00 00 00 00 00 00 00 movabsq $0, %rax > 0000000000000347: R_X86_64_64 memset > 34f: ff e0 > > Such code results in infinite recursion at runtime. This is observed > when doing kexec. > > Instead, reuse an implementation from arch/x86/boot/compressed/string.c > if we define warn as a symbol. > > Link: https://bugs.chromium.org/p/chromium/issues/detail?id=984056 > Reported-by: Vaibhav Rustagi <vaibhavrustagi@xxxxxxxxxx> > Tested-by: Vaibhav Rustagi <vaibhavrustagi@xxxxxxxxxx> > Debugged-by: Vaibhav Rustagi <vaibhavrustagi@xxxxxxxxxx> > Debugged-by: Manoj Gupta <manojgupta@xxxxxxxxxx> > Suggested-by: Alistair Delva <adelva@xxxxxxxxxx> > Signed-off-by: Vaibhav Rustagi <vaibhavrustagi@xxxxxxxxxx> > Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > --- > arch/x86/purgatory/Makefile | 3 +++ > arch/x86/purgatory/purgatory.c | 6 ++++++ > arch/x86/purgatory/string.c | 23 ----------------------- > 3 files changed, 9 insertions(+), 23 deletions(-) > delete mode 100644 arch/x86/purgatory/string.c <formletter> This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly. </formletter>
