Hello,
compiling serial_sa1100.c, i get a warning
Warning: destination register same as write-back base
This is generated by the macro "get_user" in "set_modem_info",
compiling into
2329 1bc4 0000B0E4 1: ldrt r0,[r0],#0
**** Warning:destination register same as write-back base
According to the ARM-ARM, using the same register for Rn and Rd is
undefined for the post-index adressing only available for LDRT.
I do not know if this is relevant for any of the current armv-architectures,
but if so, the problem might be avoided by specifying the addr-operand
as an early-clobberer by adding the "&"-constraint modifier for the
output-parameter "x" in include/asm-arm/proc-armv/uaccess.h
#define __get_user_asm_word(x,addr,err) \
__asm__ __volatile__( \
"1: ldrt %1,[%2],#0\n" \
"2:\n" \
" .section .fixup,\"ax\"\n" \
" .align 2\n" \
"3: mvn %0, %3\n" \
" mov %1, #0\n" \
" b 2b\n" \
" .previous\n" \
" .section __ex_table,\"a\"\n" \
" .align 3\n" \
" .long 1b, 3b\n" \
" .previous" \
/* old: : "=r" (err), "=r" (x) */ \
/*new:*/: "=r" (err),"=&r" (x) \
: "r" (addr), "i" (EFAULT), "0" (err))
The compiler then generates this code :
0xc00c90d0 <set_modem_info+72>: ldrt lr, [r0]
The same fix should also apply to __get_user_asm_half :
: "=r" (err), "=&r" (x), "=&r" (__temp) \
and __get_user_asm_byte
: "=r" (err), "=&r" (x) \
However, maybe this problem only affected me because i use somewhat dated
tools (gas 2.9.1 / egcs-2.91.60)
Regards, Klaus
--
Mobotix AG
Klaus Borchers
Wingertsweilerhof 6
D-67724 Hoeringen
Germany
Tel: +49 (6302) 9223-88
Fax: +49 (6302) 9223-70
E-Mail: [EMAIL PROTECTED]
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