[build] Allow assembler section type character to vary by architecture

On some architectures (such as ARM) the "@" character is used as a
comment delimiter.  A section type argument such as "@progbits"
therefore becomes "%progbits".

This is further complicated by the fact that the "%" character has
special meaning for inline assembly when input or output operands are
used, in which cases "@progbits" becomes "%%progbits".

Allow the section type character(s) to be defined via Makefile
variables.

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

src/Makefile.housekeeping

 #
 CFLAGS		+= -include include/compiler.h
 
+# The section type character (e.g. "@" in "@progbits") varies by
+# architecture.
+#
+CFLAGS		+= -DASM_TCHAR='$(ASM_TCHAR)' -DASM_TCHAR_OPS='$(ASM_TCHAR_OPS)'
+
 # CFLAGS for specific object types
 #
 CFLAGS_c	+=
 # Device ID tables (using IDs from ROM definition file)
 #
 define obj_pci_id_asm
-	.section ".pci_devlist.$(1)", "a", @progbits
+	.section ".pci_devlist.$(1)", "a", $(ASM_TCHAR)progbits
 	.globl pci_devlist_$(1)
 pci_devlist_$(1):
 	.short ( 0x$(1) & 0xffff )

src/arch/x86/Makefile

+# Assembler section type character
+#
+ASM_TCHAR	:= @
+ASM_TCHAR_OPS	:= @
+
 # Include common x86 headers
 #
 INCDIRS		+= arch/x86/include

src/crypto/certstore.c

 #define CERT( _index, _path )						\
 	extern char stored_cert_ ## _index ## _data[];			\
 	extern char stored_cert_ ## _index ## _len[];			\
-	__asm__ ( ".section \".rodata\", \"a\", @progbits\n\t"		\
+	__asm__ ( ".section \".rodata\", \"a\", " PROGBITS "\n\t"	\
 		  "\nstored_cert_" #_index "_data:\n\t"			\
 		  ".incbin \"" _path "\"\n\t"				\
 		  "\nstored_cert_" #_index "_end:\n\t"			\

src/crypto/privkey.c

 /* Raw private key data */
 extern char private_key_data[];
 extern char private_key_len[];
-__asm__ ( ".section \".rodata\", \"a\", @progbits\n\t"
+__asm__ ( ".section \".rodata\", \"a\", " PROGBITS "\n\t"
 	  "\nprivate_key_data:\n\t"
 #ifdef PRIVATE_KEY
 	  ".incbin \"" PRIVATE_KEY "\"\n\t"

src/image/embedded.c

 #define EMBED( _index, _path, _name )					\
 	extern char embedded_image_ ## _index ## _data[];		\
 	extern char embedded_image_ ## _index ## _len[];		\
-	__asm__ ( ".section \".rodata\", \"a\", @progbits\n\t"		\
+	__asm__ ( ".section \".rodata\", \"a\", " PROGBITS "\n\t"	\
 		  "\nembedded_image_" #_index "_data:\n\t"		\
 		  ".incbin \"" _path "\"\n\t"				\
 		  "\nembedded_image_" #_index "_end:\n\t"		\

src/include/compiler.h

 /** Stringify expanded argument */
 #define _S2( x ) _S1 ( x )
 
+/* Assembler section types */
+#ifdef ASSEMBLY
+#define PROGBITS _C2 ( ASM_TCHAR, progbits )
+#define NOBITS _C2 ( ASM_TCHAR, nobits )
+#else
+#define PROGBITS_OPS _S2 ( ASM_TCHAR_OPS ) "progbits"
+#define PROGBITS _S2 ( ASM_TCHAR ) "progbits"
+#define NOBITS_OPS _S2 ( ASM_TCHAR_OPS ) "nobits"
+#define NOBITS _S2 ( ASM_TCHAR ) "nobits"
+#endif
+
 /**
  * @defgroup symmacros Macros to provide or require explicit symbols
  * @{
  */
 #ifdef ASSEMBLY
 #define PROVIDE_SYMBOL( symbol )				\
-	.section ".provided", "a", @nobits ;			\
+	.section ".provided", "a", NOBITS ;			\
 	.hidden symbol ;					\
 	.globl	symbol ;					\
 	symbol: ;						\
  */
 #ifdef ASSEMBLY
 #define PROVIDE_REQUIRING_SYMBOL()				\
-	.section ".tbl.requiring_symbols", "a", @progbits ;	\
+	.section ".tbl.requiring_symbols", "a", PROGBITS ;	\
 	__requiring_symbol__:	.byte 0 ;			\
 	.size __requiring_symbol__, . - __requiring_symbol__ ;	\
 	.previous
 #else
 #define PROVIDE_REQUIRING_SYMBOL()				\
 	__asm__ ( ".section \".tbl.requiring_symbols\", "	\
-		  "         \"a\", @progbits\n"			\
+		  "         \"a\", " PROGBITS "\n"		\
 		  "__requiring_symbol__:\t.byte 0\n"		\
 		  ".size __requiring_symbol__, "		\
 		  "      . - __requiring_symbol__\n"		\

src/include/errno.h

  * @ret error		Error
  */
 #define __einfo_error( einfo ) ( {					\
-	__asm__ ( ".section \".einfo\", \"\", @progbits\n\t"		\
+	__asm__ ( ".section \".einfo\", \"\", " PROGBITS_OPS "\n\t"	\
 		  ".align 8\n\t"					\
 		  "\n1:\n\t"						\
 		  ".long ( 4f - 1b )\n\t"				\