[v2,1/4] Align libgloss/arm and libc/sys/arm sources: Fix GetCmdLine semihosting directives

Message ID 20190802123346.5377-2-alfedotov@gmail.com
State Accepted
Commit 37e80fbb1c329ab39d154a78fa6d99f28d220dfe
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Series
  • Align libgloss/arm and libc/sys/arm sources
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Commit Message

Alexander Fedotov Aug. 2, 2019, 12:33 p.m.
Applied changes from the commit 9b11672:

	When simulating arm code, the target program startup code (crt0) uses
	semihosting invocations to get the command line from the simulator. The
	simulator returns the command line and its size into the area passed in
	parameter. (ARM 32-bit specifications :
	http://infocenter.arm.com/help/topic/com.arm.doc.dui0058d/DUI0058.pdf
	chapter "5.4.19 SYS_GET_CMDLINE").

	The memory area pointed by the semihosting register argument is located
	in .text section (usually not writtable (RX)).

	If we run this code on a simulator that respects this rights properties
	(qemu user-mode for instance), the command line will not be written to
	the .text program memory, in particular the length of the string. The
	program runs with an empty command line. This problem hasn't been seen
	earlier probably because qemu user-mode is not so much used, but this can
	happen with another simulator that refuse to write in a read-only segment.

	With this modification, the command line can be correctly passed to the
	target program.

	Changes:
	- newlib/libc/sys/arm/crt0.S : Arguments passed to the
	AngelSWI_Reason_GetCmdLine semihosting invocation are placed into .data
	section instead of .text
---
 newlib/libc/sys/arm/crt0.S | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

-- 
2.17.1

Patch

diff --git a/newlib/libc/sys/arm/crt0.S b/newlib/libc/sys/arm/crt0.S
index 9c262428d..40bbc3d69 100644
--- a/newlib/libc/sys/arm/crt0.S
+++ b/newlib/libc/sys/arm/crt0.S
@@ -393,13 +393,14 @@  __change_mode:
 	movs	r1, r0
 #else
 	movs	r0, #AngelSWI_Reason_GetCmdLine
-	adr	r1, .LC30	/* Space for command line.  */
+	ldr	r1, .LC30	/* Space for command line.  */
 #ifdef THUMB_VXM
 	bkpt	AngelSWI
 #else
  	AngelSWIAsm	AngelSWI
 #endif
 	ldr	r1, .LC30
+	ldr	r1, [r1]
 #endif
 	/*  Parse string at r1.  */
 	movs	r0, #0		/* Count of arguments so far.  */
@@ -586,8 +587,7 @@  change_back:
 #endif
 #ifdef ARM_RDI_MONITOR
 .LC30:
-	.word	CommandLine
-	.word	255
+	.word	AngelSWIArgs
 .LC31:
 	.word	__end__
 
@@ -600,6 +600,9 @@  HeapLimit:	.word	0
 __stack_base__:	.word	0
 StackLimit:	.word	0
 CommandLine:	.space	256,0	/*  Maximum length of 255 chars handled.  */
+AngelSWIArgs:
+	.word	CommandLine
+	.word	255
 #endif
 	
 #ifdef __pe__