On Thu, Feb 22, 2018 at 11:40:41AM +0100, Arnd Bergmann wrote: > gcc-8 warns that we copy TRAMPOLINE_32BIT_CODE_SIZE bytes from the pointer > to the function into actual trampoline, when that pointer is only 8 bytes: > > In file included from arch/x86/boot/compressed/pgtable_64.c:3: > arch/x86/boot/compressed/pgtable_64.c: In function 'paging_prepare': > arch/x86/boot/compressed/../string.h:18:23: error: '__builtin_memcpy' reading > 96 bytes from a region of size 8 [-Werror=stringop-overflow=] > #define memcpy(d,s,l) __builtin_memcpy(d,s,l) > ^~~~~~~~~~~~~~~~~~~~~~~ > arch/x86/boot/compressed/pgtable_64.c:62:2: note: in expansion of macro > 'memcpy' > memcpy(trampoline + TRAMPOLINE_32BIT_CODE_OFFSET / sizeof(unsigned long), > ^~~~~~ > > I assume what was intended here is to copy the trampoline itself rather than > the pointer to the trampoline. > > Cc: Martin Sebor <[email protected]> > Fixes: b91993a87aff ("x86/boot/compressed/64: Prepare trampoline memory") > Signed-off-by: Arnd Bergmann <[email protected]> > --- > This is a fairly new warning in gcc, it's possible that the code is > correct and the warning message got it wrong, please double-check this. > > Was the 32-bit trampoline code in the 64-bit decompressor tested successfully?
Yes, it was. Actually it tested on every boot of any 64-bit machine. The fix is wrong and it breaks boot. The bug is in trampoline_32bit_src declaration. Could you check if this helps with the warning: diff --git a/arch/x86/boot/compressed/pgtable.h b/arch/x86/boot/compressed/pgtable.h index 6e0db2260147..5e0b1c4abef4 100644 --- a/arch/x86/boot/compressed/pgtable.h +++ b/arch/x86/boot/compressed/pgtable.h @@ -12,7 +12,7 @@ #ifndef __ASSEMBLER__ -extern void (*trampoline_32bit_src)(void *return_ptr); +extern void trampoline_32bit_src(void *return_ptr); #endif /* __ASSEMBLER__ */ #endif /* BOOT_COMPRESSED_PAGETABLE_H */ -- Kirill A. Shutemov
