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Re: Update on wip-arm-bootstrap


From: Danny Milosavljevic
Subject: Re: Update on wip-arm-bootstrap
Date: Mon, 22 Feb 2021 02:03:30 +0100

Hi Janneke,

Nice!

Patch review:

>+#if __ARM_EABI__
>+#define CLEAR_CACHE(BEG,END)                                          \
>+{                                                                     \
>+  register unsigned long _beg __asm ("a1") = (unsigned long)(BEG);    \
>+  register unsigned long _end __asm ("a2") = (unsigned long)(END);    \
>+  register unsigned long _flg __asm ("a3") = 0;                               
>\
>+  __asm __volatile ("mov r7, 0x9f0002\n\t"                            \

should be mov r7, 0xf0002 in EABI.
(SWI #(0x900000 + syscallnr) is for OABI syscalls only)

>* sysdeps/unix/sysv/linux/arm/brk.c (__brk): Likewise.Likewise.

Duplicate "Likewise".

Otherwise LGTM!

>But something like puts or printf segfaults "Illegal
>instruction" in strlen:

>--8<---------------cut here---------------start------------->8---
>(gdb) disas /r
>Dump of assembler code for function strlen:
>   0x0000d160 <+0>:    03 10 c0 e3     bic     r1, r0, #3
>=> 0x0000d164 <+4>:    04 20 91 e4     ldr     r2, [r1], #4  
>--8<---------------cut here---------------end--------------->8---

Hmm... looks good to me?  Weird.

I'm building it right now and will have a look.

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