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 assume the > linker logic is that it's branching to a thumb function but the target > is already the +1 so no action necessary, as opposed to just blindly > adding 1. > > -Christoffer -- 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
