56 lines
2.2 KiB
Diff
56 lines
2.2 KiB
Diff
|
From 238050dfd46e3c4a87329da1d48b4d8dde5af8a1 Mon Sep 17 00:00:00 2001
|
||
|
|
From: Michael Brown <mcb30@ipxe.org>
|
||
|
|
Date: Fri, 7 Jun 2013 13:46:27 +0100
|
||
|
|
Subject: [PATCH] [build] Work around bug in gcc >= 4.8
|
||
|
|
|
||
|
|
gcc 4.8 and 4.9 fail to compile pxe_call.c with the error "bp cannot
|
||
|
|
be used in asm here". Other points in the codebase which use "ebp" in
|
||
|
|
the asm clobber list do not seem to be affected.
|
||
|
|
|
||
|
|
Unfortunately gcc provides no way to specify %ebp as an output
|
||
|
|
register, so we cannot use this as a workaround. The only viable
|
||
|
|
solution is to explicitly push/pop %ebp within the asm itself. This
|
||
|
|
is ugly for two reasons: firstly, it may be unnecessary; secondly, it
|
||
|
|
may cause gcc to generate invalid %esp-relative addresses if the asm
|
||
|
|
happens to use memory operands. This specific block of asm uses no
|
||
|
|
memory operands and so will not generate invalid code.
|
||
|
|
|
||
|
|
Reported-by: Daniel P. Berrange <berrange@redhat.com>
|
||
|
|
Reported-by: Christian Hesse <list@eworm.de>
|
||
|
|
Originally-fixed-by: Christian Hesse <list@eworm.de>
|
||
|
|
Signed-off-by: Michael Brown <mcb30@ipxe.org>
|
||
|
|
---
|
||
|
|
roms/ipxe/src/arch/i386/interface/pxe/pxe_call.c | 8 +++++---
|
||
|
|
1 file changed, 5 insertions(+), 3 deletions(-)
|
||
|
|
|
||
|
|
Index: b/roms/ipxe/src/arch/i386/interface/pxe/pxe_call.c
|
||
|
|
===================================================================
|
||
|
|
--- a/roms/ipxe/src/arch/i386/interface/pxe/pxe_call.c
|
||
|
|
+++ b/roms/ipxe/src/arch/i386/interface/pxe/pxe_call.c
|
||
|
|
@@ -265,12 +265,14 @@ int pxe_start_nbp ( void ) {
|
||
|
|
DBG ( "Restarting NBP (%x)\n", jmp );
|
||
|
|
|
||
|
|
/* Far call to PXE NBP */
|
||
|
|
- __asm__ __volatile__ ( REAL_CODE ( "movw %%cx, %%es\n\t"
|
||
|
|
+ __asm__ __volatile__ ( REAL_CODE ( "pushl %%ebp\n\t" /* gcc bug */
|
||
|
|
+ "movw %%cx, %%es\n\t"
|
||
|
|
"pushw %%es\n\t"
|
||
|
|
"pushw %%di\n\t"
|
||
|
|
"sti\n\t"
|
||
|
|
"lcall $0, $0x7c00\n\t"
|
||
|
|
- "addw $4, %%sp\n\t" )
|
||
|
|
+ "popl %%ebp\n\t" /* discard */
|
||
|
|
+ "popl %%ebp\n\t" /* gcc bug */ )
|
||
|
|
: "=a" ( rc ), "=b" ( discard_b ),
|
||
|
|
"=c" ( discard_c ), "=d" ( discard_d ),
|
||
|
|
"=D" ( discard_D )
|
||
|
|
@@ -278,7 +280,7 @@ int pxe_start_nbp ( void ) {
|
||
|
|
"c" ( rm_cs ),
|
||
|
|
"d" ( virt_to_phys ( &pxenv ) ),
|
||
|
|
"D" ( __from_text16 ( &ppxe ) )
|
||
|
|
- : "esi", "ebp", "memory" );
|
||
|
|
+ : "esi", "memory" );
|
||
|
|
|
||
|
|
return rc;
|
||
|
|
}
|