When a pbl image uncompress and call the normal barebox, In
barebox_non_pbl_start() it should call relocate_to_adr() to relocate barebox
to barebox_base. Ofcouse CONFIG_RELOCATABLE enabled.
And barebox_base calculated by:
#define barebox_image_size (unsigned int)&_barebox_image_size
unsigned long barebox_size = barebox_image_size +
((unsigned long)&__bss_stop - (unsigned long)&__bss_start);
_barebox_image_size, __bss_stop, __bss_start all defined in linkscript
"arch/arm/lib32/barebox.lds.S"
But when I print there value in function barebox_non_pbl_start() with the
flowwing code:
putc_ll('X');
putc_ll('\r');
putc_ll('\n');
PUTHEX_LL(barebox_size);
putc_ll('\r');
putc_ll('\n');
PUTHEX_LL((unsigned long)&__bss_start);
putc_ll('\r');
putc_ll('\n');
PUTHEX_LL((unsigned long)&__bss_stop);
putc_ll('\r');
putc_ll('\n');
The result as floww:
X
00000000
00000000
00000000
It's so strange, SO objdump it:
00017424 <barebox_non_pbl_start>:
17424: e59f61a0 ldr r6, [pc, #416] ; 175cc <barebox_non_pbl_start+0x1a8>
17428: e080a001 add sl, r0, r1
1742c: e59f919c ldr r9, [pc, #412] ; 175d0 <barebox_non_pbl_start+0x1ac>
17430: e1a08000 mov r8, r0
17434: e92d4890 push {r4, r7, fp, lr}
17438: e0895006 add r5, r9, r6
1743c: e59fb190 ldr fp, [pc, #400] ; 175d4 <barebox_non_pbl_start+0x1b0>
17440: e3a00058 mov r0, #88 ; 0x58
17444: e1a07002 mov r7, r2
17448: ebfffca7 bl 166ec <PUTC_LL>
1744c: e06b5005 rsb r5, fp, r5
17450: e3a0000d mov r0, #13
17454: ebfffca4 bl 166ec <PUTC_LL>
17458: e3a0000a mov r0, #10
1745c: ebfffca2 bl 166ec <PUTC_LL>
17460: e1a00005 mov r0, r5
17464: ebffffe0 bl 173ec <PUTHEX_LL>
17468: e3a0000d mov r0, #13
1746c: ebfffc9e bl 166ec <PUTC_LL>
17470: e3a0000a mov r0, #10
17474: ebfffc9c bl 166ec <PUTC_LL>
17478: e1a0000b mov r0, fp
1747c: ebffffda bl 173ec <PUTHEX_LL>
17480: e3a0000d mov r0, #13
17484: ebfffc98 bl 166ec <PUTC_LL>
17488: e3a0000a mov r0, #10
1748c: ebfffc96 bl 166ec <PUTC_LL>
17490: e1a00006 mov r0, r6
17494: e24a6906 sub r6, sl, #98304 ; 0x18000
17498: ebffffd3 bl 173ec <PUTHEX_LL>
1749c: e3c66dff bic r6, r6, #16320 ; 0x3fc0
174a0: e3a0000d mov r0, #13
......
175c4: ebffa2c5 bl e0 <mem_malloc_init>
175c8: ebffa5a5 bl c64 <start_barebox>
175cc: 00000000 andeq r0, r0, r0
175d0: 00000000 andeq r0, r0, r0
175d4: 00000000 andeq r0, r0, r0
175d8: 00022448 andeq r2, r2, r8, asr #8
175dc: d00dfeed andle pc, sp, sp, ror #29
We can see it save __bss_start and __bss_stop in local literal pool located at
175cc and 175d0, The value is zero. But in barebox.map it's
0x00000000000207b0 . = ALIGN (0x4)
0x00000000000207b0 __bss_start = .
......
0x0000000000022458 __bss_stop = .
0x0000000000022458 _end = .
0x00000000000207b0 _barebox_image_size = __bss_start
Why?? It's so strange! Is it a bug of toolchain?
My toolchain is:
arm-poky-linux-gnueabi-gcc (GCC) 5.3.0
GNU ld (GNU Binutils) 2.26.0.20160214
I test this situation with a newer toolchain:
arm-poky-eabi-gcc (GCC) 8.2.0
GNU ld (GNU Binutils) 2.31.1.20180818
With this toolchain the printhex_ll output value for __bss_start and
__bss_stop same as them in barebox.map. This cofused me more!!
And with new toolchain there is a new thing: As barebox_non_pbl_start()
running address is not it's link address. So if use PUTS_LL(const char *str)
It should crash. but it sure works. I check the dis-asm code. Found the
linker/gcc add some code to using the string ptr pc relatived. Does this the
new toolchain's benifit? And who ? gcc or linker ?
The flowwing patch let _barebox_image_size has right value
-----------------------------------8<-----------------------------
>From 29420237496b23c97de03c189529b223902653aa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=BC=A0=E5=BF=A0=E5=B1=B1?= <zzs213@xxxxxxx>
Date: Mon, 17 Jun 2019 17:43:44 +0800
Subject: [PATCH] bugfix: _barebox_image_size wrong if enable
CONFIG_RELOCATABLE
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Signed-off-by: 张忠山 <zzs213@xxxxxxx>
---
arch/arm/lib32/barebox.lds.S | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/arch/arm/lib32/barebox.lds.S b/arch/arm/lib32/barebox.lds.S
index 53a5f55cc..49224a79c 100644
--- a/arch/arm/lib32/barebox.lds.S
+++ b/arch/arm/lib32/barebox.lds.S
@@ -20,16 +20,18 @@
#include <asm-generic/barebox.lds.h>
+#ifdef CONFIG_RELOCATABLE
+#define BASE 0x0
+#else
+#define BASE TEXT_BASE
+#endif
+
OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")
OUTPUT_ARCH(arm)
ENTRY(start)
SECTIONS
{
-#ifdef CONFIG_RELOCATABLE
- . = 0x0;
-#else
- . = TEXT_BASE;
-#endif
+ . = BASE;
#ifndef CONFIG_PBL_IMAGE
PRE_IMAGE
@@ -124,5 +126,5 @@ SECTIONS
.bss : { *(.bss*) }
__bss_stop = .;
_end = .;
- _barebox_image_size = __bss_start - TEXT_BASE;
+ _barebox_image_size = __bss_start - BASE;
}
--
2.21.0
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