From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.kymetacorp.com ([192.81.58.21]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1a4IeY-0002bi-6O for barebox@lists.infradead.org; Thu, 03 Dec 2015 01:25:46 +0000 From: Trent Piepho Date: Thu, 3 Dec 2015 01:24:56 +0000 Message-ID: <1449105900.26955.1.camel@rtred1test09.kymeta.local> Content-Language: en-US Content-ID: MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: [PATCH] ARM: Remove kernel booting call for thumb2 mode To: barebox The asm code to do the actual call into the kernel (or another barebox) when compiled in thumb2 mode isn't necessary. gcc generates a perfectly good calling sequence from a normal function pointer call. If it didn't, the code in bootstrap_boot() that uses a function pointer to jump to the 2nd stage barebox from an xloader wouldn't work. It appears to be allowed that the call to kernel() could return, as neither start_linux() nor kernel() are marked noreturn, and there is code after calls to start_linux(). The asm code has a bug in this case, as it uses bx and not blx, and thus doesn't set the link register. Since it's a tail call, this would be okay, but only if the LR value from the start of start_linux() (and the callee-saved registers) are restored beforehand, which isn't done. The gcc generated call sequence will do this. Signed-off-by: Trent Piepho --- arch/arm/lib/armlinux.c | 12 ------------ 1 file changed, 12 deletions(-) diff --git a/arch/arm/lib/armlinux.c b/arch/arm/lib/armlinux.c index 16879f8..47b9bd3 100644 --- a/arch/arm/lib/armlinux.c +++ b/arch/arm/lib/armlinux.c @@ -277,17 +277,5 @@ void start_linux(void *adr, int swap, unsigned long initrd_address, __asm__ __volatile__("mcr p15, 0, %0, c1, c0" :: "r" (reg)); } -#ifdef CONFIG_THUMB2_BAREBOX - __asm__ __volatile__ ( - "mov r0, #0\n" - "mov r1, %0\n" - "mov r2, %1\n" - "bx %2\n" - : - : "r" (architecture), "r" (params), "r" (kernel) - : "r0", "r1", "r2" - ); -#else kernel(0, architecture, params); -#endif } -- 1.8.3.1 _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox