Messages in this thread |  | | Subject | Re: Build regressions/improvements in v5.5-rc2 | From | Greg Ungerer <> | Date | Tue, 17 Dec 2019 10:56:39 +1000 |
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Hi Geert,
On 16/12/19 6:49 pm, Geert Uytterhoeven wrote: > Hi Greg, > > On Mon, Dec 16, 2019 at 9:38 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote: >> Below is the list of build error/warning regressions/improvements in >> v5.5-rc2[1] compared to v5.4[2]. > >> [1] http://kisskb.ellerman.id.au/kisskb/branch/linus/head/d1eef1c619749b2a57e514a3fa67d9a516ffa919/ (all 232 configs) >> [2] http://kisskb.ellerman.id.au/kisskb/branch/linus/head/219d54332a09e8d8741c1e1982f5eae56099de85/ (all 232 configs) > >> + /kisskb/src/arch/m68k/include/asm/string.h: warning: '__builtin_memcpy' forming offset [3, 4] is out of the bounds [0, 2] of object '__gu_val' with type 'short unsigned int' [-Warray-bounds]: => 72:25 > > The upgrade from gcc 4.6.3 to 81.0 seems to have revealed a potential > issue in get_user() in arch/m68k/include/asm/uaccess_no.h. > > #define get_user(x, ptr) \ > ({ \ > int __gu_err = 0; \ > typeof(x) __gu_val = 0; \ > ^^^^^^^^^ > This is the type of the destination > > switch (sizeof(*(ptr))) { \ > case 1: \ > __get_user_asm(__gu_err, __gu_val, ptr, b, "=d"); \ > break; \ > case 2: \ > __get_user_asm(__gu_err, __gu_val, ptr, w, "=r"); \ > break; \ > case 4: \ > __get_user_asm(__gu_err, __gu_val, ptr, l, "=r"); \ > break; \ > case 8: \ > memcpy((void *) &__gu_val, ptr, sizeof (*(ptr))); \ > break; \ > default: \ > __gu_val = 0; \ > __gu_err = __get_user_bad(); \ > break; \ > } \ > (x) = (typeof(*(ptr))) __gu_val; \ > __gu_err; \ > }) > > ext2_ioctl() calls this like > > unsigned short rsv_window_size; > if (get_user(rsv_window_size, (int __user *)arg)) { ... } > > So a 32-bit value is being copied to an unsigned short value, leading > to the warning (for the memcpy() in the non-taken "case 8" branch). > > Fortunately the compiler emits a register move for this, so no real harm > is done: > > | fs/ext2/ioctl.c:123: if (get_user(rsv_window_size, > (int __user *)arg)) > move.l 48(%sp),%a0 | arg, > #APP > | 123 "fs/ext2/ioctl.c" 1 > movel (%a0),%d2 | *arg.32_43, __gu_val > > The corresponding code in arch/m68k/include/asm/uaccess_mm.h > uses a temporary __gu_val of the right sized type based on the source > type to avoid this.
Yeah, your right. I will put a change together to fix.
Regards Greg
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