Messages in this thread | | | From | Ard Biesheuvel <> | Date | Wed, 20 Jun 2018 00:23:56 +0200 | Subject | Re: [PATCH 0/2] Make badr macro compatible with newer GAS versions |
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On 19 June 2018 at 22:45, Guenter Roeck <linux@roeck-us.net> wrote: > On Tue, Jun 19, 2018 at 10:34:38PM +0200, Ard Biesheuvel wrote: >> On 19 June 2018 at 22:32, Guenter Roeck <linux@roeck-us.net> wrote: >> > On Tue, Jun 19, 2018 at 09:26:31PM +0200, Ard Biesheuvel wrote: >> >> Work around the mindless and backward incompatible change in GAS that >> >> prevents us from using a simple addition to set the Thumb bit in local >> >> symbol references taken using 'adr' instructions (#2) >> >> >> >> As a preparatory step, remove badr occurrences in ARM code sequences >> >> contained in Thumb2 kernels. >> >> >> >> Ard Biesheuvel (2): >> >> ARM: avoid badr macro for switching to Thumb-2 mode >> >> ARM: assembler: prevent ADR from setting the Thumb bit twice >> >> >> > >> > This doesn't work for images built with a toolchain based on gcc 7.3.0 >> > and binutils 2.28.1. It _does_ work for images built with gcc 7.3.0/ >> > binutils 2.30. >> > >> >> Sigh. >> >> So does it fail? Or is the resulting binary broken? > > Hard to say. It crashes early in boot, even before earlycon can say > anything. >
OK, so even the linker handling is inconsistent.
Working (binutils 2.30)
c0301164 <local_restart>: c0301164: f8d9 a000 ldr.w sl, [r9] c0301168: e92d 0030 stmdb sp!, {r4, r5} c030116c: f01a 0ff0 tst.w sl, #240 ; 0xf0 c0301170: d117 bne.n c03011a2 <__sys_trace> c0301172: 46ba mov sl, r7 c0301174: f5ba 7fc8 cmp.w sl, #400 ; 0x190 c0301178: bf28 it cs c030117a: f04f 0a00 movcs.w sl, #0 c030117e: f3af 8014 csdb c0301182: f2af 1e83 subw lr, pc, #387 ; 0x183 c0301182: R_ARM_THM_ALU_PREL_11_0 .Lsym28
Broken (binutils 2.26)
c0301184 <local_restart>: c0301184: f8d9 a000 ldr.w sl, [r9] c0301188: e92d 0030 stmdb sp!, {r4, r5} c030118c: f01a 0ff0 tst.w sl, #240 ; 0xf0 c0301190: d117 bne.n c03011c2 <__sys_trace> c0301192: 46ba mov sl, r7 c0301194: f5ba 7fc8 cmp.w sl, #400 ; 0x190 c0301198: bf28 it cs c030119a: f04f 0a00 movcs.w sl, #0 c030119e: f3af 8014 csdb c03011a2: f2af 1ea2 subw lr, pc, #418 ; 0x1a2 c03011a2: R_ARM_THM_ALU_PREL_11_0 .Lsym30
Note the even immediate in the subw instruction. So this is another dead end, unfortunately.
Thanks for testing.
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