Dave Martin <dave.mar...@arm.com> writes: > On Wed, Sep 02, 2015 at 08:23:29AM +0200, Robert Jarzmik wrote: >> On old ARM chips, unaligned accesses to memory are not trapped and >> fixed. On module load, symbols are relocated, and the relocation of >> __bug_table symbols is done on a u32 basis. Yet the section is not >> aligned to a multiple of 4 address, but to a multiple of 2.
Hi Russell, I dug deeper, and got another stack, unrelated to modules insertion but related to alignement fault (see [1] for reference). As before, this didn't happen on v4.1, but happens on linux-next. I'm wondering if alignement fixup does work in my case and if I understand it. This time I took my JTAG to have a look at the flow, in arch/arm/mm/alignment.c, where I added the small chunk in [2], which gave in my case : RJK: fault=4 instr=0x00000000 instrptr=0xc02b37c8 thumb_mode=0 tinstr=0x0000 The instruction (as seen with vmlinux disassembly or JTAG memory dump) is : 0xc02b37c8 <+372>: b2 50 c6 10 strhne r5, [r6], #2 I must admit I fail to see how the following "fixup:" label can be reached with a "missed" copy_from_user() (fault == 4). This is probably what happened to me with the modules __bug_table section, and it will continue to happen until I understand why this copy fails. It's really odd nobody but me faces this issue. Cheers. -- Robert [1] New stack ============= #0: pxa2xx-ac97 (Wolfson WM9713,WM9714) RJK: fault=4 instr=0x00000000 instrptr=0xc02b37c8 thumb_mode=0 tinstr=0x0000 &Unable to handle kernel paging request at virtual address c3057661 &pgd = c0004000 "[c3057661] *pgd=a300040e(bad) Internal error: Oops: 803 [#1] PREEMPT ARM Modules linked in: CPU: 0 PID: 1 Comm: swapper Not tainted 4.2.0-rc8-next-20150828+ #900 Hardware name: MIO A701 task: c3858bc0 ti: c385c000 task.ti: c385c000 PC is at doc_read_data_area+0x174/0x370 LR is at doc_read_page_getbytes+0x58/0x78 pc : [<c02b37c8>] lr : [<c02b3a1c>] psr: a8000013 sp : c385d8e0 ip : c07142b8 fp : c385d91c r10: c3aac540 r9 : c070ffc0 r8 : c385c000 @QGi r7 : 00000002 r6 : c3057661 r5 : 0000c1e5 r4 : 0000000b r3 : 0000000a r2 : 0000000b r1 : c3057661 r0 : 00000000 Flags: NzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none Control: 0000397f Table: a0004000 DAC: 00000053 Process swapper (pid: 1, stack limit = 0xc385c198) Stack: (0xc385d8e0 to 0xc385e000) d8e0: 00000000 c02b3a34 00000001 0000000a c385d914 c3057660 0000000c c3aac540 ... chop chop ... dfe0: 00000000 00000000 00000000 00000000 00000013 00000000 f3ff8cdd 4cf3d76f [<c02b37c8>] (doc_read_data_area) from [<c02b3a1c>] (doc_read_page_getbytes+0x58/0x78) [<c02b3a1c>] (doc_read_page_getbytes) from [<c02b5f20>] (doc_read_oob+0x22c/0x75c) [<c02b5f20>] (doc_read_oob) from [<c02b64b4>] (doc_read+0x64/0x74) [<c02b64b4>] (doc_read) from [<c02ade08>] (part_read+0x58/0x9c) [<c02ade08>] (part_read) from [<c02aa8d8>] (mtd_read+0x88/0xbc) [<c02aa8d8>] (mtd_read) from [<c02c35ec>] (ubi_io_read+0x16c/0x358) [<c02c35ec>] (ubi_io_read) from [<c02c0450>] (ubi_eba_read_leb+0x384/0x4d4) [<c02c0450>] (ubi_eba_read_leb) from [<c02bf944>] (ubi_leb_read+0xd4/0x134) [<c02bf944>] (ubi_leb_read) from [<c0185e9c>] (ubifs_leb_read+0x3c/0xa8)s [<c0185e9c>] (ubifs_leb_read) from [<c019fd94>] (ubifs_read_nnode+0xec/0x200) [<c019fd94>] (ubifs_read_nnode) from [<c01a03a0>] (ubifs_lpt_lookup_dirty+0x38/0x330) [<c01a03a0>] (ubifs_lpt_lookup_dirty) from [<c0190448>] (ubifs_replay_journal+0x3c/0x1b38) [<c0190448>] (ubifs_replay_journal) from [<c0182c38>] (ubifs_mount+0x1444/0x2410) [<c0182c38>] (ubifs_mount) from [<c00eb604>] (mount_fs+0x24/0xb0) [<c00eb604>] (mount_fs) from [<c01081d0>] (vfs_kern_mount+0x58/0x124) [<c01081d0>] (vfs_kern_mount) from [<c010b384>] (do_mount+0xb40/0xd10) [<c010b384>] (do_mount) from [<c010b8a8>] (SyS_mount+0x84/0xb0) [<c010b8a8>] (SyS_mount) from [<c068319c>] (mount_block_root+0x12c/0x2dc) [<c068319c>] (mount_block_root) from [<c0683564>] (prepare_namespace+0x98/0x1bc) [<c0683564>] (prepare_namespace) from [<c0682eb4>] (kernel_init_freeable+0x188/0x1d4) [<c0682eb4>] (kernel_init_freeable) from [<c04a2610>] (kernel_init+0x18/0xfc) [<c04a2610>] (kernel_init) from [<c000a5ec>] (ret_from_fork+0x14/0x28) Code: 1a000060 e51b3030 e3560000 e2877002 (10c650b2) ---[ end trace a0bcca195299a22d ]--- [2] Debug patch =============== diff --git a/arch/arm/mm/alignment.c b/arch/arm/mm/alignment.c index 2c0c541c60ca..b0897da5456c 100644 --- a/arch/arm/mm/alignment.c +++ b/arch/arm/mm/alignment.c @@ -787,6 +787,8 @@ do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs) instr = __mem_to_opcode_arm(instr); } + pr_info("RJK: fault=%d instr=0x%08lx instrptr=0x%08lx thumb_mode=%lu tinstr=0x%04x\n", + fault, instr, instrptr, thumb_mode(regs), tinstr); if (fault) { type = TYPE_FAULT; goto bad_or_fault; [3] Abort stack =============== #0 panic (fmt=0xc385d6c4 <incomplete sequence \344>) at kernel/panic.c:72 #1 0xc000e788 in oops_end (regs=<optimized out>, signr=<optimized out>, flags=<optimized out>) at arch/arm/kernel/traps.c:311 #2 die (str=0x68000013 "", regs=<optimized out>, err=-1014638958) at arch/arm/kernel/traps.c:333 #3 0xc00137c0 in __do_kernel_fault (mm=0xc06e8c04 <init_mm>, addr=3271915105, fsr=2051, regs=0xc385d890) at arch/arm/mm/fault.c:150 #4 0xc0013b10 in do_bad_area (addr=<optimized out>, fsr=<optimized out>, regs=<optimized out>) at arch/arm/mm/fault.c:198 #5 0xc00166c8 in do_alignment (addr=3271915105, fsr=2051, regs=0xc385d890) at arch/arm/mm/alignment.c:900 #6 0xc0009264 in do_DataAbort (addr=3271915105, fsr=2051, regs=0xc385d890) at arch/arm/mm/fault.c:550 #7 0xc000f024 in __dabt_svc () at arch/arm/kernel/entry-armv.S:204 [4] frame #6 regs dump ====================== $1 = {uregs = {0, 3271915105, 11, 10, 11, 49637, 3271915105, 2, 3280322560, 3228630976, 3282748736, 3280328988, 3228648120, 3280328928, 3224058396, 3224057800, 2818572307, 4294967295}} -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/