On Mon, May 11, 2015 at 10:44:49AM +0100, Ard Biesheuvel wrote: > On 11 May 2015 at 11:05, Christoffer Dall <christoffer.dall@xxxxxxxxxx> wrote: > > On Sat, May 09, 2015 at 10:10:56PM +0200, Ard Biesheuvel wrote: > >> On 9 May 2015 at 22:07, Christoffer Dall <christoffer.dall@xxxxxxxxxx> wrote: > >> > On Fri, May 08, 2015 at 05:08:42PM +0100, Russell King wrote: > >> >> BSYM() should only be used when refering to local symbols in the same > >> >> assembly file which are resolved by the assembler, and not for > >> >> linker-fixed up symbols. The use of BSYM() with panic is incorrect as > >> >> the linker is involved in fixing up this relocation, and it knows > >> >> whether panic() is ARM or Thumb. > >> >> > >> >> Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx> > >> >> --- > >> >> arch/arm/kvm/interrupts.S | 2 +- > >> >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> >> > >> >> diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S > >> >> index 79caf79b304a..87847d2c5f99 100644 > >> >> --- a/arch/arm/kvm/interrupts.S > >> >> +++ b/arch/arm/kvm/interrupts.S > >> >> @@ -309,7 +309,7 @@ ENTRY(kvm_call_hyp) > >> >> THUMB( orr r2, r2, #PSR_T_BIT ) > >> >> msr spsr_cxsf, r2 > >> >> mrs r1, ELR_hyp > >> >> - ldr r2, =BSYM(panic) > >> >> + ldr r2, =panic > >> >> msr ELR_hyp, r2 > >> >> ldr r0, =\panic_str > >> >> clrex @ Clear exclusive monitor > >> >> -- > >> >> 1.8.3.1 > >> >> > >> > Indeed, the linker figures it out as it should. It does seem like the > >> > right result is produced with the BSYM() macro as well so not sure what > >> > the harm is. > >> > > >> > >> BSYM() is defined as 'sym + 1' not 'sym | 1', so if the symbol has the > >> thumb bit set already, the result is incorrect. > >> > > yeah, but the linker will look at the result of 'sym + 1', so on my > > system it ends up with 'sym + 1' after the linker has done its thing > > (verified by looking at the disassembly of vmlinux); > > Hmm, I though had done the same when this was under discussion a > couple of weeks ago, and had arrived at the opposite conclusion, but > now I cannot reproduce anymore so apparently not. > Sorry for the noise. I think that was me confusing myself. In fact, the linker behaves differently depending on the target symbol type. If the relevant symbols are all correctly annoted with .type %function or ENDPROC, the linker should do the right thing without needing any BSYMs. Cheers ---Dave -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
