| Message ID | 1441175009-26730-1-git-send-email-robert.jarzmik@free.fr (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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. > > This triggers an Oops on pxa architecture, where address 0xbf0021ea > is the first relocation in the __bug_table section : > apply_relocate(): pxa3xx_nand: section 13 reloc 0 sym '' > Unable to handle kernel paging request at virtual address bf0021ea > pgd = e1cd0000 > [bf0021ea] *pgd=c1cce851, *pte=c1cde04f, *ppte=c1cde01f > Internal error: Oops: 23 [#1] ARM > Modules linked in: > CPU: 0 PID: 606 Comm: insmod Not tainted 4.2.0-rc8-next-20150828-cm-x300+ #887 > Hardware name: CM-X300 module > task: e1c68700 ti: e1c3e000 task.ti: e1c3e000 > PC is at apply_relocate+0x2f4/0x3d4 > LR is at 0xbf0021ea > pc : [<c000e7c8>] lr : [<bf0021ea>] psr: 80000013 > sp : e1c3fe30 ip : 60000013 fp : e49e8c60 > r10: e49e8fa8 r9 : 00000000 r8 : e49e7c58 > r7 : e49e8c38 r6 : e49e8a58 r5 : e49e8920 r4 : e49e8918 > r3 : bf0021ea r2 : bf007034 r1 : 00000000 r0 : bf000000 > Flags: Nzcv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none > Control: 0000397f Table: c1cd0018 DAC: 00000051 > Process insmod (pid: 606, stack limit = 0xe1c3e198) > [<c000e7c8>] (apply_relocate) from [<c005ce5c>] (load_module+0x1248/0x1f5c) > [<c005ce5c>] (load_module) from [<c005dc54>] (SyS_init_module+0xe4/0x170) > [<c005dc54>] (SyS_init_module) from [<c000a420>] (ret_fast_syscall+0x0/0x38) > > Fix this by ensuring entries in __bug_table are all aligned to at least > of multiple of 4. This transforms a module section __bug_table as : > - [12] __bug_table PROGBITS 00000000 002232 000018 00 A 0 0 1 > + [12] __bug_table PROGBITS 00000000 002232 000018 00 A 0 0 4 > > Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr> > --- > arch/arm/include/asm/bug.h | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/arm/include/asm/bug.h b/arch/arm/include/asm/bug.h > index b274bde24905..e7335a92144e 100644 > --- a/arch/arm/include/asm/bug.h > +++ b/arch/arm/include/asm/bug.h > @@ -40,6 +40,7 @@ do { \ > "2:\t.asciz " #__file "\n" \ > ".popsection\n" \ > ".pushsection __bug_table,\"a\"\n" \ > + ".align 2\n" \ > "3:\t.word 1b, 2b\n" \ > "\t.hword " #__line ", 0\n" \ > ".popsection"); \ Reviewed-by: Dave Martin <Dave.Martin@arm.com> I added the .align in my recent patches implementing BUG for arm64, but didn't touch arch/arm. When referring to the arm code I did notice that there was no .align. I'd concluded that the linker script layout and lack of bug reports meant the arm code was alignment-safe in practice, but I guess I was mistaken... Cheers ---Dave
diff --git a/arch/arm/include/asm/bug.h b/arch/arm/include/asm/bug.h index b274bde24905..e7335a92144e 100644 --- a/arch/arm/include/asm/bug.h +++ b/arch/arm/include/asm/bug.h @@ -40,6 +40,7 @@ do { \ "2:\t.asciz " #__file "\n" \ ".popsection\n" \ ".pushsection __bug_table,\"a\"\n" \ + ".align 2\n" \ "3:\t.word 1b, 2b\n" \ "\t.hword " #__line ", 0\n" \ ".popsection"); \
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. This triggers an Oops on pxa architecture, where address 0xbf0021ea is the first relocation in the __bug_table section : apply_relocate(): pxa3xx_nand: section 13 reloc 0 sym '' Unable to handle kernel paging request at virtual address bf0021ea pgd = e1cd0000 [bf0021ea] *pgd=c1cce851, *pte=c1cde04f, *ppte=c1cde01f Internal error: Oops: 23 [#1] ARM Modules linked in: CPU: 0 PID: 606 Comm: insmod Not tainted 4.2.0-rc8-next-20150828-cm-x300+ #887 Hardware name: CM-X300 module task: e1c68700 ti: e1c3e000 task.ti: e1c3e000 PC is at apply_relocate+0x2f4/0x3d4 LR is at 0xbf0021ea pc : [<c000e7c8>] lr : [<bf0021ea>] psr: 80000013 sp : e1c3fe30 ip : 60000013 fp : e49e8c60 r10: e49e8fa8 r9 : 00000000 r8 : e49e7c58 r7 : e49e8c38 r6 : e49e8a58 r5 : e49e8920 r4 : e49e8918 r3 : bf0021ea r2 : bf007034 r1 : 00000000 r0 : bf000000 Flags: Nzcv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none Control: 0000397f Table: c1cd0018 DAC: 00000051 Process insmod (pid: 606, stack limit = 0xe1c3e198) [<c000e7c8>] (apply_relocate) from [<c005ce5c>] (load_module+0x1248/0x1f5c) [<c005ce5c>] (load_module) from [<c005dc54>] (SyS_init_module+0xe4/0x170) [<c005dc54>] (SyS_init_module) from [<c000a420>] (ret_fast_syscall+0x0/0x38) Fix this by ensuring entries in __bug_table are all aligned to at least of multiple of 4. This transforms a module section __bug_table as : - [12] __bug_table PROGBITS 00000000 002232 000018 00 A 0 0 1 + [12] __bug_table PROGBITS 00000000 002232 000018 00 A 0 0 4 Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr> --- arch/arm/include/asm/bug.h | 1 + 1 file changed, 1 insertion(+)