svn commit: r323409 - in stable/11/sys/boot: arm/uboot uboot/common

[Ian Lepore]

Author: ian
Date: Mon Sep 11 00:55:18 2017
New Revision: 323409
URL: https://svnweb.freebsd.org/changeset/base/323409

Log:
  MFC r316374, r316377:
  
  Preserve the registers containing argc, argv, and return address values
  passed in from u-boot across the call to self_reloc and any other early-init
  code, and restore them before calling main().
  
  Correct a comment... the stack used by ubldr is the same stack u-boot was
  running on when it jumped to the ubldr entry point.  None of the arches
  that use this code set up a different stack in their start.S routines.

Modified:
  stable/11/sys/boot/arm/uboot/start.S
  stable/11/sys/boot/uboot/common/main.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/sys/boot/arm/uboot/start.S
==============================================================================
--- stable/11/sys/boot/arm/uboot/start.S	Mon Sep 11 00:51:47 2017	(r323408)
+++ stable/11/sys/boot/arm/uboot/start.S	Mon Sep 11 00:55:18 2017	(r323409)
@@ -45,6 +45,13 @@ _start:
 	orr	ip, ip, #(CPU_CONTROL_AFLT_ENABLE)
 	mcr     p15, 0, ip, c1, c0, 0
 #endif
+
+	/*
+	 * Save r0 and r1 (argc and argv passed from u-boot), and lr (trashed
+	 * by the call to self_reloc below) until we're ready to call main().
+	 */
+	push	{r0, r1, lr}
+
 	/* 
 	 * Do self-relocation when the weak external symbol _DYNAMIC is non-NULL.
 	 * When linked as a dynamic relocatable file, the linker automatically
@@ -71,9 +78,11 @@ _start:
 	str	r9, [ip, #4]
 
 	/* 
+	 * First restore argc, argv, and the u-boot return address, then
 	 * Start loader.  This is basically a tail-recursion call; if main()
 	 * returns, it returns to u-boot (which reports the value returned r0).
 	 */
+	pop	{r0, r1, lr}
 	b	main
 
 	/* 

Modified: stable/11/sys/boot/uboot/common/main.c
==============================================================================
--- stable/11/sys/boot/uboot/common/main.c	Mon Sep 11 00:51:47 2017	(r323408)
+++ stable/11/sys/boot/uboot/common/main.c	Mon Sep 11 00:55:18 2017	(r323409)
@@ -416,7 +416,9 @@ main(int argc, char **argv)
 
 	/*
 	 * Initialise the heap as early as possible.  Once this is done,
-	 * alloc() is usable. The stack is buried inside us, so this is safe.
+	 * alloc() is usable.  We are using the stack u-boot set up near the top
+	 * of physical ram; hopefully there is sufficient space between the end
+	 * of our bss and the bottom of the u-boot stack to avoid overlap.
 	 */
 	uboot_heap_start = round_page((uintptr_t)end);
 	uboot_heap_end   = uboot_heap_start + 512 * 1024;