| Message ID | 20150419192836.GO12732@n2100.arm.linux.org.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 19 April 2015 at 21:28, Russell King - ARM Linux <linux@arm.linux.org.uk> wrote: > On Sun, Apr 19, 2015 at 07:41:08PM +0200, Ard Biesheuvel wrote: >> I am away from my work pc so i can't check but i wonder if all setup >> functions are correctly annotated as thumb2 when built in thumb2 mode. >> If not, it would explain why a plain branch works but doing arithmetic >> on the address doesn't. > > Yes, it's a Thumb2 kernel, but more importantly, it's a nommu kernel, > and the nommu code wasn't touched. > > So, the entry code looks like this: > > 28008000: f8df 9024 ldr.w r9, [pc, #36] ; 28008028 <__after_proc_init+0x4> > 28008004: f8d9 9000 ldr.w r9, [r9] > 28008008: f001 f926 bl 28009258 <__lookup_processor_type> > 2800800c: ea5f 0a05 movs.w sl, r5 > 28008010: f001 8164 beq.w 280092dc <__error_p> > 28008014: f8df d014 ldr.w sp, [pc, #20] ; 2800802c <__after_proc_init+0x8> > 28008018: f20f 0e07 addw lr, pc, #7 > 2800801c: f10a 0c10 add.w ip, sl, #16 > 28008020: 46e7 mov pc, ip > 28008022: e7ff b.n 28008024 <__after_proc_init> > > which results in us jumping to: > > 2822091c <__proc_info_begin>: > 2822091c: 000f0000 andeq r0, pc, r0 > 28220920: 000f0000 andeq r0, pc, r0 > ... > 2822092c: fff5ce6d ; <UNDEFINED> instruction: 0xfff5ce6d > > ^^^ here. That's an offset from the beginning of the structure, which > gives us an address of 0x2817d789, which would be correct: > > 2817d788 <__v7m_setup>: > 2817d788: 4829 ldr r0, [pc, #164] ; (2817d830 <v7m_processor_functions+0x30>) > 2817d78a: f8df c0a8 ldr.w ip, [pc, #168] ; 2817d834 <v7m_processor_functions+0x34> > 2817d78e: f8c0 c008 str.w ip, [r0, #8] > > The patch below should resolve it - Joachim, please confirm: Yep, patch below makes Linus master boot again on my Cortex-M4 board. Tested-by: Joachim Eastwood <manabian@gmail.com> Thanks for debugging and fixing the problem Russell. regards, Joachim Eastwood > diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S > index 455033110078..5925449f6f04 100644 > --- a/arch/arm/kernel/head-nommu.S > +++ b/arch/arm/kernel/head-nommu.S > @@ -80,9 +80,9 @@ ENTRY(stext) > ldr r13, =__mmap_switched @ address to jump to after > @ initialising sctlr > adr lr, BSYM(1f) @ return (PIC) address > - ARM( add pc, r10, #PROCINFO_INITFUNC ) > - THUMB( add r12, r10, #PROCINFO_INITFUNC ) > - THUMB( ret r12 ) > + ldr r12, [r10, #PROCINFO_INITFUNC] > + add r12, r12, r10 > + ret r12 > 1: b __after_proc_init > ENDPROC(stext) > > @@ -117,9 +117,9 @@ ENTRY(secondary_startup) > > adr lr, BSYM(__after_proc_init) @ return address > mov r13, r12 @ __secondary_switched address > - ARM( add pc, r10, #PROCINFO_INITFUNC ) > - THUMB( add r12, r10, #PROCINFO_INITFUNC ) > - THUMB( ret r12 ) > + ldr r12, [r10, #PROCINFO_INITFUNC] > + add r12, r12, r10 > + ret r12 > ENDPROC(secondary_startup) > > ENTRY(__secondary_switched) > > > -- > FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up > according to speedtest.net.
diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S index 455033110078..5925449f6f04 100644 --- a/arch/arm/kernel/head-nommu.S +++ b/arch/arm/kernel/head-nommu.S @@ -80,9 +80,9 @@ ENTRY(stext) ldr r13, =__mmap_switched @ address to jump to after @ initialising sctlr adr lr, BSYM(1f) @ return (PIC) address - ARM( add pc, r10, #PROCINFO_INITFUNC ) - THUMB( add r12, r10, #PROCINFO_INITFUNC ) - THUMB( ret r12 ) + ldr r12, [r10, #PROCINFO_INITFUNC] + add r12, r12, r10 + ret r12 1: b __after_proc_init ENDPROC(stext) @@ -117,9 +117,9 @@ ENTRY(secondary_startup) adr lr, BSYM(__after_proc_init) @ return address mov r13, r12 @ __secondary_switched address - ARM( add pc, r10, #PROCINFO_INITFUNC ) - THUMB( add r12, r10, #PROCINFO_INITFUNC ) - THUMB( ret r12 ) + ldr r12, [r10, #PROCINFO_INITFUNC] + add r12, r12, r10 + ret r12 ENDPROC(secondary_startup) ENTRY(__secondary_switched)