| Message ID | 20180222104101.2717185-1-arnd@arndb.de |
|---|---|
| State | New |
| Headers | show |
| Series | x86/boot/compressed/64: fix warning for 32-bit trampoline copy | expand |
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: 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
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
diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c index dad5da7b4c1a..35a0542fe397 100644 --- a/arch/x86/boot/compressed/pgtable_64.c +++ b/arch/x86/boot/compressed/pgtable_64.c @@ -60,7 +60,7 @@ struct paging_config paging_prepare(void) /* Copy trampoline code in place */ memcpy(trampoline + TRAMPOLINE_32BIT_CODE_OFFSET / sizeof(unsigned long), - &trampoline_32bit_src, TRAMPOLINE_32BIT_CODE_SIZE); + trampoline_32bit_src, TRAMPOLINE_32BIT_CODE_SIZE); /* * Set up a new page table that will be used for switching from 4-
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? --- arch/x86/boot/compressed/pgtable_64.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.9.0