Messages in this thread | | | From | Arnd Bergmann <> | Date | Thu, 22 Feb 2018 12:24:25 +0100 | Subject | Re: [PATCH] x86/boot/compressed/64: fix warning for 32-bit trampoline copy |
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On Thu, Feb 22, 2018 at 12:02 PM, Kirill A. Shutemov <kirill@shutemov.name> wrote: > 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 <msebor@gmail.com> >> Fixes: b91993a87aff ("x86/boot/compressed/64: Prepare trampoline memory") >> Signed-off-by: Arnd Bergmann <arnd@arndb.de> >> --- >> 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:
Got it, yes that definitely explains the problem. Your patch fixes it and I'll follow up with a new submission using this change, unless you want to send it as a patch yourself.
Arnd
> 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
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