[librm] Ensure that inline code symbols are unique

Commit 6149e0a ("[librm] Provide symbols for inline code placed into
other sections") may cause build failures due to duplicate label names
if the compiler chooses to duplicate inline assembly code.

Fix by using the "%=" special format string to include a
guaranteed-unique number within the label name.

The "%=" will be expanded only if constraints exist for the inline
assembly.  This fix therefore requires that all REAL_CODE() fragments
use a (possibly empty) constraint list.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/x86/core/dumpregs.c

 		TEXT16_CODE ( ".globl dump_regs\n\t"
 			      "\ndump_regs:\n\t"
 			      VIRT_CALL ( _dump_regs )
-			      "ret\n\t" ) );
+			      "ret\n\t" ) : );
 
 	printf ( "EAX=%08x EBX=%08x ECX=%08x EDX=%08x\n"
 		 "ESI=%08x EDI=%08x EBP=%08x ESP=%08x\n"

src/arch/x86/include/librm.h

 #endif
 
 /* LINE_SYMBOL: declare a symbol for the current source code line */
-#define LINE_SYMBOL _S2 ( OBJECT ) "__line_" _S2 ( __LINE__ ) ":"
+#define LINE_SYMBOL _S2 ( OBJECT ) "__line_" _S2 ( __LINE__ ) "__%=:"
 
 /* TEXT16_CODE: declare a fragment of code that resides in .text16 */
 #define TEXT16_CODE( asm_code_str )			\

src/arch/x86/interface/pcbios/bios_console.c

 	__asm__ __volatile__ (
 		TEXT16_CODE ( "\nint16_wrapper:\n\t"
 			      "pushfw\n\t"
-			      "cmpb $0, %cs:bios_inject_lock\n\t"
+			      "cmpb $0, %%cs:bios_inject_lock\n\t"
 			      "jnz 1f\n\t"
 			      VIRT_CALL ( bios_inject )
 			      "\n1:\n\t"
 			      "popfw\n\t"
-			      "ljmp *%cs:int16_vector\n\t" ) );
+			      "ljmp *%%cs:int16_vector\n\t" ) : );
 
 	/* Hook INT 16 */
 	hook_bios_interrupt ( 0x16, ( ( intptr_t ) int16_wrapper ),

src/arch/x86/interface/pcbios/bios_reboot.c

 	put_real ( flag, BDA_SEG, BDA_REBOOT );
 
 	/* Jump to system reset vector */
-	__asm__ __volatile__ ( REAL_CODE ( "ljmp $0xf000, $0xfff0" ) );
+	__asm__ __volatile__ ( REAL_CODE ( "ljmp $0xf000, $0xfff0" ) : );
 }
 
 /**

src/arch/x86/interface/syslinux/comboot_call.c

 			      VIRT_CALL ( int20 )
 			      "clc\n\t"
 			      "call patch_cf\n\t"
-		              "iret\n\t" ) );
+		              "iret\n\t" ) : );
 
 	hook_bios_interrupt ( 0x20, ( intptr_t ) int20_wrapper, &int20_vector );
 
 			      VIRT_CALL ( int21 )
 			      "clc\n\t"
 			      "call patch_cf\n\t"
-		              "iret\n\t" ) );
+		              "iret\n\t" ) : );
 
 	hook_bios_interrupt ( 0x21, ( intptr_t ) int21_wrapper, &int21_vector );
 
 			      VIRT_CALL ( int22 )
 			      "clc\n\t"
 			      "call patch_cf\n\t"
-		              "iret\n\t" ) );
+		              "iret\n\t" ) : );
 
 	hook_bios_interrupt ( 0x22, ( intptr_t ) int22_wrapper, &int22_vector );
 }

src/arch/x86/transitions/librm_test.c

 	/* Profile complete real-mode call cycle */
 	for ( i = 0 ; i < PROFILE_COUNT ; i++ ) {
 		profile_start ( &real_call_profiler );
-		__asm__ __volatile__ ( REAL_CODE ( "" ) );
+		__asm__ __volatile__ ( REAL_CODE ( "" ) : );
 		profile_stop ( &real_call_profiler );
 	}