From: Julian Seward <jseward@acm.org>
Date: Tue, 22 Mar 2005 02:03:09 +0000 (+0000)
Subject: Finally finish pissing around with jmp_with_stack.  Now at least we
X-Git-Tag: svn/VALGRIND_3_0_0~915
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=10d241c300e4cfd6552fda25c334bd92fc06bdaa;p=thirdparty%2Fvalgrind.git

Finally finish pissing around with jmp_with_stack.  Now at least we
can get a startup on amd64.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@3403
---

diff --git a/coregrind/amd64/jmp_with_stack.c b/coregrind/amd64/jmp_with_stack.c
index 068b52450b..1b7033e5a8 100644
--- a/coregrind/amd64/jmp_with_stack.c
+++ b/coregrind/amd64/jmp_with_stack.c
@@ -45,24 +45,26 @@
    "   movq $0, %r15\n"
 
 
-/* Call f(), but first switch stacks, using 'stack' as the new stack,
-   and use 'retaddr' as f's return-to address.  Also, clear all the
-   integer registers before entering f. */
+/* Jump to 'dst', but first set the stack pointer to 'stack'.  Also,
+   clear all the integer registers before entering 'dst'.  It's
+   important that the stack pointer is set to exactly 'stack' and not
+   (eg) stack - apparently_harmless_looking_small_offset.  Basically
+   because the code at 'dst' might be wanting to scan the area above
+   'stack' (viz, the auxv array), and putting spurious words on the
+   stack confuses it.
+*/
 /*
 __attribute__((noreturn))
-void call_on_new_stack_0_0 ( Addr stack,
-			     Addr retaddr,
-			     void (*f)(void) );
+void jump_and_switch_stacks ( Addr stack, Addr dst );
+
   %rdi == stack
-  %rsi == retaddr
-  %rdx == f
+  %rsi == dst
 */
 asm(
-".global call_on_new_stack_0_0\n"
-"call_on_new_stack_0_0:\n"
+".global jump_and_switch_stacks\n"
+"jump_and_switch_stacks:\n"
 "   movq   %rdi, %rsp\n"  /* set stack */
-"   pushq  %rsi\n"        /* retaddr to stack */
-"   pushq  %rdx\n"        /* f to stack*/
+"   pushq  %rsi\n"        /* f to stack*/
     ZERO_ALL_INT_REGS
 "   ret\n"                /* jump to f */
 "   ud2\n"                /* should never get here */
diff --git a/coregrind/stage1.c b/coregrind/stage1.c
index 6ab8c93cd4..42a80fabb0 100644
--- a/coregrind/stage1.c
+++ b/coregrind/stage1.c
@@ -337,8 +337,8 @@ int main(int argc, char** argv)
 
    /* move onto another stack so we can play with the main one */
    jump_and_switch_stacks(
-      (Addr)stack + sizeof(stack),  /* stack */
-      main2                         /* where to */
+      (Addr) stack + sizeof(stack),  /* stack */
+      (Addr) main2                   /* where to */
    );
 
    /*NOTREACHED*/