Messages in this thread | | | Subject | Re: arm: Remaining issue with alignment of __log_buf in printk.c | From | Jonathan Cameron <> | Date | Sun, 27 May 2012 18:01:28 +0100 |
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Russell King - ARM Linux <linux@arm.linux.org.uk> wrote:
>On Sun, May 27, 2012 at 10:03:20AM -0600, Stephen Warren wrote: >> On 05/27/2012 06:39 AM, Jonathan Cameron wrote: >> > Hi All, >> > >> > My stargate 2 board refused to start and after bisection I ended >> > up at the same patch that Stephen found an alignment issue in. >> > Unfortunately Stephen's patch doesn't seem to have fixed the >> > issue for me. >> > https://lkml.org/lkml/2012/5/10/510 is the thread. Patch from >> > Stephen is : f8450fca6ecdea38b5a882fdf6cd097e3ec8651c >> > >> > Increasing the alignement for 32 bit systems to 8 seems to do the >> > job but I can't immediately think why... >> > >> > System is a pxa27x strong arm. > >First thing to point out is that PXA27x is Xscale, not StrongARM. Sorry my mistake! > >> The first element in the structure type that's actually stored in the >> __log_buf array is a u64; see struct log in kernel/printk.c. >Depending >> on alignment rules, a u64 and a struct containing it might require a >> 4-byte or 8-byte alignment. The following link implies this might >have >> changed over time: >> >> http://wiki.debian.org/ArmEabiPort#Struct_packing_and_alignment >> >> (see "64-bit data type alignment" a little below that anchor). I'm >not >> sure what ABI the kernel expects to use internally, or your compiler; >> perhaps you need the new EABI 8-byte alignment requirement for a u64 >and >> hence the struct as a whole, but Tegra (or my toolchain?) is OK with >the >> older 4-byte alignment for a u64 or struct? >> >> Further, I'm not sure if the following alignment selection logic: >> >> > #if !defined(CONFIG_64BIT) || >defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) >> > #define LOG_ALIGN 4 >> > #else >> > #define LOG_ALIGN 8 >> > #endif >> >> ... uses the CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS for its intended >> purpose? >> >> Russell, can you please comment here. Thanks. > >And most likely it's using EABI which does want 8 byte alignment. Indeed I am using eabi. So >this >should probably be fixed for EABI builds.
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