On 19 June 2018 at 09:48, Ard Biesheuvel <ard.biesheu...@linaro.org> wrote: > On 19 June 2018 at 07:07, Guenter Roeck <li...@roeck-us.net> wrote: >> Modern assemblers may take the ISA into account when resolving local >> symbols. This can result in bad address calculations when using badr >> in the wrong location since the offset + 1 may be added twice, resulting >> in an even address target for THUMB instructions. This in turn results >> in an exception at (destination address + 2). >> >> Unhandled exception: IPSR = 00000006 LR = fffffff1 >> CPU: 0 PID: 1 Comm: init Not tainted 4.18.0-rc1-00026-gf773e5bdf0c9 #15 >> Hardware name: MPS2 (Device Tree Support) >> PC is at ret_fast_syscall+0x2/0x58 >> LR is at tty_ioctl+0x2a5/0x528 >> pc : [<21009002>] lr : [<210d1535>] psr: 4000000b >> sp : 21825fa8 ip : 0000001c fp : 21a95892 >> r10: 00000000 r9 : 21824000 r8 : 210091c0 >> r7 : 00000036 r6 : 21ae1ee0 r5 : 00000000 r4 : 21ae1f3c >> r3 : 00000000 r2 : 3d9adc25 r1 : 00000000 r0 : 00000000 >> xPSR: 4000000b >> CPU: 0 PID: 1 Comm: init Not tainted 4.18.0-rc1-00026-gf773e5bdf0c9 #15 >> Hardware name: MPS2 (Device Tree Support) >> [<2100bd8d>] (unwind_backtrace) from [<2100b13b>] (show_stack+0xb/0xc) >> [<2100b13b>] (show_stack) from [<2100b87b>] (__invalid_entry+0x4b/0x4c) >> >> Fix the problem by using a logical or instead of an addition. This is >> less efficient but guaranteed to work. >> >> Signed-off-by: Guenter Roeck <li...@roeck-us.net> >> --- >> RFC: I don't really like this, but my ARM assembler knowledge is quite >> limited. Just dropping the "+ 1" from badr doesn't work because some >> other code needs it (the image hangs completely if I try that). >> Ultimately I don't even know if the invoke_syscall macro should just >> have used adr instead of badr (but then how did this ever work ?). >> >> Seen with various toolchains based on gcc 7.x and binutils 2.30 when >> building and testing MPS2 images. >> > > Hello Guenter, > > This issue has been discussed before. It appears the binutils people > suddenly started caring about the thumb annotation of local function > symbols, resulting in behavior that is not backwards compatible. > > https://marc.info/?l=linux-arm-kernel&m=151143776213636&w=2 > https://sourceware.org/bugzilla/show_bug.cgi?id=21458 > > Can you try the fix below please? > >> arch/arm/include/asm/assembler.h | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/arch/arm/include/asm/assembler.h >> b/arch/arm/include/asm/assembler.h >> index 0cd4dccbae78..24c87ff2060f 100644 >> --- a/arch/arm/include/asm/assembler.h >> +++ b/arch/arm/include/asm/assembler.h >> @@ -195,7 +195,8 @@ >> .irp c,,eq,ne,cs,cc,mi,pl,vs,vc,hi,ls,ge,lt,gt,le,hs,lo >> .macro badr\c, rd, sym >> #ifdef CONFIG_THUMB2_KERNEL >> - adr\c \rd, \sym + 1 >> + adr\c \rd, \sym >> + orr \rd, #1 >> #else >> adr\c \rd, \sym >> #endif >> -- >> 2.7.4 > > ----------8<------------ > From: Ard Biesheuvel <ard.biesheu...@linaro.org> > Date: Tue, 16 Jan 2018 12:12:45 +0000 > Subject: [PATCH] ARM: assembler: prevent ADR from setting the Thumb bit twice > > To work around recent issues where ADR references to Thumb function > symbols may or may not have the Thumb bit set already when they are > resolved by GAS, reference the symbol indirectly via a local symbol > typed as 'object', stripping the ARM/Thumb annotation. > > Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org> > > diff --git a/arch/arm/include/asm/assembler.h > b/arch/arm/include/asm/assembler.h > index 6ae42ad29518..dd2ff94ad90b 100644 > --- a/arch/arm/include/asm/assembler.h > +++ b/arch/arm/include/asm/assembler.h > @@ -195,13 +195,19 @@ > .irp c,,eq,ne,cs,cc,mi,pl,vs,vc,hi,ls,ge,lt,gt,le,hs,lo > .macro badr\c, rd, sym > #ifdef CONFIG_THUMB2_KERNEL > - adr\c \rd, \sym + 1 > + __badr \c, \rd, \sym > #else > adr\c \rd, \sym > #endif > .endm > .endr > > + /* this needs to be a separate macro or \@ does not work correctly */ > + .macro __badr, c, rd, sym > + .eqv .Lsym\@, \sym > + adr\c \rd, .Lsym\@ + 1 > + .endm > + > /* > * Get current thread_info. > */
Never mind - it doesn't work. (I tested it locally but with the wrong kernel)
