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[build] Work around bug in gcc >= 4.8

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Commit 238050d ("[build] Work around bug in gcc >= 4.8") works around
one instance of a bug in recent versions of gcc, in which "ebp" cannot
be specified within an asm clobber list.

Some versions of gcc seem to exhibit the same bug on other points in
the codebase.  Fix by changing all instances of "ebp" in a clobber
list to use the push/pop %ebp workaround instead.

Originally-implemented-by: Víctor Román Archidona <contacto@victor-roman.es>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2013-09-25 12:55:46 +01:00
parent a9fa0d5f2b
commit cba22d36b7
6 changed files with 35 additions and 20 deletions
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7
src/arch/i386/image/bootsector.c
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@@ -80,6 +80,8 @@ int call_bootsector ( unsigned int segment, unsigned int offset,
"movw %%ss, %%ax\n\t"
"movw %%ax, %%cs:saved_ss\n\t"
"movw %%sp, %%cs:saved_sp\n\t"
/* Save frame pointer (gcc bug) */
"movl %%ebp, %%cs:saved_ebp\n\t"
/* Prepare jump to boot sector */
"pushw %%bx\n\t"
"pushw %%di\n\t"
@@ -99,11 +101,14 @@ int call_bootsector ( unsigned int segment, unsigned int offset,
"sti\n\t"
"lret\n\t"
/* Preserved variables */
"\nsaved_ebp: .long 0\n\t"
"\nsaved_ss: .word 0\n\t"
"\nsaved_sp: .word 0\n\t"
"\nsaved_retaddr: .word 0\n\t"
/* Boot failure return point */
"\nbootsector_exec_fail:\n\t"
/* Restore frame pointer (gcc bug) */
"movl %%cs:saved_ebp, %%ebp\n\t"
/* Restore stack pointer */
"movw %%cs:saved_ss, %%ax\n\t"
"movw %%ax, %%ss\n\t"
@@ -114,7 +119,7 @@ int call_bootsector ( unsigned int segment, unsigned int offset,
"=d" ( discard_d )
: "b" ( segment ), "D" ( offset ),
"d" ( drive )
: "eax", "ecx", "esi", "ebp" );
: "eax", "ecx", "esi" );
DBG ( "Booted disk returned via INT 18 or 19\n" );