cmd/ld, cmd/5l: support R_ARM_PC24 and R_ARM_JUMP24, fix R_ARM_CALL

1. R_ARM_CALL can also be used to call a PLT entry
2. add support for R_ARM_PC24 and R_ARM_JUMP24
3. refactor, remove D_PLT32 in favor of D_CALL

Fixes #4006.

R=rsc, dave
CC=fullung, golang-dev
https://golang.org/cl/6622057

src/cmd/5l/5.out.h

@@ -270,8 +270,7 @@ enum	as
 #define	D_PLT0		(D_NONE+43) // R_ARM_PLT32, 1st inst: add ip, pc, #0xNN00000
 #define	D_PLT1		(D_NONE+44) // R_ARM_PLT32, 2nd inst: add ip, ip, #0xNN000
 #define	D_PLT2		(D_NONE+45) // R_ARM_PLT32, 3rd inst: ldr pc, [ip, #0xNNN]!
-#define	D_PLT32 	(D_NONE+46) // R_ARM_PLT32, bl xxxxx
-#define	D_CALL		(D_NONE+47) // R_ARM_CALL, bl xxxxx
+#define	D_CALL		(D_NONE+46) // R_ARM_PLT32/R_ARM_CALL/R_ARM_JUMP24, bl xxxxx or b yyyyy
 
 /*
  * this is the ranlib header

src/cmd/5l/asm.c

@@ -137,7 +137,7 @@ adddynrel(Sym *s, Reloc *r)
 
 	// Handle relocations found in ELF object files.
 	case 256 + R_ARM_PLT32:
-		r->type = D_PLT32;
+		r->type = D_CALL;
 		if(targ->dynimpname != nil && !targ->dynexport) {
 			addpltsym(targ);
 			r->sym = lookup(".plt", 0);
@@ -184,7 +184,11 @@ adddynrel(Sym *s, Reloc *r)
 
 	case 256 + R_ARM_CALL:
 		r->type = D_CALL;
-		r->add += 0;
+		if(targ->dynimpname != nil && !targ->dynexport) {
+			addpltsym(targ);
+			r->sym = lookup(".plt", 0);
+			r->add = braddoff(r->add, targ->plt / 4);
+		}
 		return;
 
 	case 256 + R_ARM_REL32: // R_ARM_REL32
@@ -206,6 +210,16 @@ adddynrel(Sym *s, Reloc *r)
 		}
 		r->sym = S;
 		return;
+
+	case 256 + R_ARM_PC24:
+	case 256 + R_ARM_JUMP24:
+		r->type = D_CALL;
+		if(targ->dynimpname != nil && !targ->dynexport) {
+			addpltsym(targ);
+			r->sym = lookup(".plt", 0);
+			r->add = braddoff(r->add, targ->plt / 4);
+		}
+		return;
 	}
 	
 	// Handle references to ELF symbols from our own object files.
@@ -290,21 +304,19 @@ archreloc(Reloc *r, Sym *s, vlong *val)
 		*val = 0xe5bcf000U +
 			(0xfff & (uint32)(symaddr(r->sym) - (symaddr(lookup(".plt", 0)) + r->off) + r->add + 8));
 		return 0;
-	case D_PLT32: // bl XXXXXX or b YYYYYY in R_ARM_PLT32
-		*val = (0xff000000U & (uint32)r->add) +
-			(0xffffff & (uint32)((symaddr(r->sym) + (0xffffffU & (uint32)r->add) * 4) - (s->value + r->off)) / 4);
-		return 0;
-	case D_CALL: // bl XXXXXX
-		*val = braddoff(0xeb000000U, (0xffffff & (uint32)((symaddr(r->sym) + ((uint32)r->add) * 4 - (s->value + r->off)) / 4)));
-		return 0;
-	}
-	return -1;
+	case D_CALL: // bl XXXXXX or b YYYYYY
+		*val = braddoff((0xff000000U & (uint32)r->add), 
+		                (0xffffff & (uint32)
+		                   ((symaddr(r->sym) + ((uint32)r->add) * 4 - (s->value + r->off)) / 4)));
+	return 0;
+}
+return -1;
 }
 
 static Reloc *
 addpltreloc(Sym *plt, Sym *got, Sym *sym, int typ)
 {
-	Reloc *r;
+Reloc *r;
 	r = addrel(plt);
 	r->sym = got;
 	r->off = plt->size;

src/cmd/ld/elf.h

@@ -564,6 +564,7 @@ typedef struct {
 #define	R_ARM_GOT32		26	/* Add PC-relative GOT offset. */
 #define	R_ARM_PLT32		27	/* Add PC-relative PLT offset. */
 #define	R_ARM_CALL		28
+#define	R_ARM_JUMP24	29
 #define	R_ARM_V4BX		40
 #define	R_ARM_GOT_PREL		96
 #define	R_ARM_GNU_VTENTRY	100
@@ -575,7 +576,7 @@ typedef struct {
 #define	R_ARM_RPC24		254
 #define	R_ARM_RBASE		255
 
-#define	R_ARM_COUNT		33	/* Count of defined relocation types. */
+#define	R_ARM_COUNT		37	/* Count of defined relocation types. */
 
 
 #define	R_386_NONE	0	/* No relocation. */

src/cmd/ld/ldelf.c

@@ -852,6 +852,8 @@ reltype(char *pn, int elftype, uchar *siz)
 	case R('5', R_ARM_CALL):
 	case R('5', R_ARM_V4BX):
 	case R('5', R_ARM_GOT_PREL):
+	case R('5', R_ARM_PC24):
+	case R('5', R_ARM_JUMP24):
 	case R('6', R_X86_64_PC32):
 	case R('6', R_X86_64_PLT32):
 	case R('6', R_X86_64_GOTPCREL):