From b57dc4a49242a5f0ae5d166690655f2611645e56 Mon Sep 17 00:00:00 2001
From: Freya Murphy <freya@freyacat.org>
Date: Thu, 12 Sep 2024 09:42:04 -0400
Subject: [PATCH] align segments

---
 masm/a.out    | Bin 0 -> 4848 bytes
 masm/asm.c    |  34 +++++++++++++++++++++++++++-------
 masm/asm.h    |   1 +
 masm/out.o    | Bin 0 -> 4632 bytes
 masm/test.asm |   5 +++++
 5 files changed, 33 insertions(+), 7 deletions(-)
 create mode 100755 masm/a.out
 create mode 100644 masm/out.o

diff --git a/masm/a.out b/masm/a.out
new file mode 100755
index 0000000000000000000000000000000000000000..0a4bfeeb799397dfee57890906b085444ad10641
GIT binary patch
literal 4848
zcmeHLJxc>Y5Pf&iBw~?^S_l@NjUNb6B%p=pfkqH4Y^=`<IX@tJa<`(X%pVY}{15&k
zOG`V^KcH`RbB6{CE2|xt-FZ82=JwupbJsf9b6f|7xu`OB5a^R8P=9`qun8Y77EwW&
zhy@-rCy*qw#z*zJ$u|*r#({C>#aYWbYgPfPfK|XMU=^?mSOu&CRspMkRlq7>6|f5Y
zs{+m&{EZG;KHXjGFO)xUxLL!|{VOKm?FM+nG|>0l7fe<?R7<?wS={X={!Nm0JHOvG
zFvsMY!9svlIU#m+M&<$rOS@wDFoMr_;tJ;qn$KAH<9d$3fF}GJ^S%IDQ7d3jKZW2S
zuNVGwUeC#c;91sdBbNGQgNn(-Jo(#lHsG%f@z;m)Tg1UP{?3nla;+K(PNN<&l|sdt
zLU?+G@T3!|h?|OUc@nm>EX-7tDqKY8mk48%jxRgpFbOoW-i3<V+*NA!vpmv08fl_y
z8hVxc{LyB}6CKLtKl#@v^p|)<7TO$LcrJOXREJ*V7#44_G>A*of$yx}T4q1FNe?m8
q%fwtoL&pce8ItZR-<8XZ(dFF+RzGI2pCj&hzdGaZyeHz7Vcr+**G{JZ

literal 0
HcmV?d00001

diff --git a/masm/asm.c b/masm/asm.c
index 1050b18..883cb55 100644
--- a/masm/asm.c
+++ b/masm/asm.c
@@ -17,6 +17,8 @@ extern char *current_file;
 #define SYMSEC_STUB -1
 #define SYMSEC_EXTERN -1
 
+#define SEC_ALIGN 0x1000
+
 static int create_symbol(struct assembler *assembler,
 			 const char name[MAX_LEX_LENGTH],
 			 ssize_t section_idx,
@@ -338,7 +340,7 @@ static int assemble_phdr(struct assembler *assembler, Elf32_Phdr **res,
 		hdr->p_paddr = 0;
 		hdr->p_filesz = htonl(size);
 		hdr->p_memsz = htonl(size);
-		hdr->p_align = htonl(0x1000);
+		hdr->p_align = htonl(SEC_ALIGN);
 	}
 
 	*res = phdr;
@@ -530,17 +532,30 @@ static void update_offsets(struct assembler *assembler, Elf32_Ehdr *ehdr)
 		ptr += len * sizeof(Elf32_Rela);
 	}
 
+	// section padding
+	{
+		uint32_t mod = ptr % SEC_ALIGN;
+		if (mod != 0)
+			assembler->secalign = (SEC_ALIGN - mod);
+		else
+			assembler->secalign = 0;
+		ptr += assembler->secalign;
+	}
+
 	// sections
+	size_t v_addr = 0x00400000;
 	for (uint32_t i = 0; i < assembler->sectab.len; i++) {
 		struct section *sec = &assembler->sectab.sections[i];
-		int idx = sec->shdr_idx;
+		uint32_t idx = sec->shdr_idx;
+		uint32_t size = ntohl(phdr[i].p_filesz);
 		phdr[i].p_offset = htonl(ptr);
-		phdr[i].p_vaddr = htonl(ptr);
-		phdr[i].p_paddr = htonl(ptr);
+		phdr[i].p_vaddr = htonl(v_addr);
+		phdr[i].p_paddr = htonl(v_addr);
 		shdr[idx].sh_offset = htonl(ptr);
 		shdr[idx].sh_size = phdr[i].p_filesz;
 		shdr[idx].sh_addr = phdr[i].p_vaddr;
-		ptr += ntohl(phdr[i].p_filesz);
+		v_addr += size;
+		ptr += size;
 	}
 
 	// symtab
@@ -567,8 +582,7 @@ static void update_offsets(struct assembler *assembler, Elf32_Ehdr *ehdr)
 
 static void update_sym_shindx(struct assembler *assembler)
 {
-	for (size_t i = 0; i < assembler->symtab.len; i++)
-	{
+	for (size_t i = 0; i < assembler->symtab.len; i++) {
 		Elf32_Sym *sym = &assembler->symtab.symbols[i];
 		ssize_t sec = assembler->symtab.sections[i];
 
@@ -605,6 +619,12 @@ static int write_file(struct assembler *assembler, Elf32_Ehdr *ehdr,
 		fwrite(ptr, sizeof(Elf32_Rela), len, out);
 	}
 
+	// section padding
+	for (uint32_t i = 0; i < assembler->secalign; i++) {
+		uint8_t zero = 0;
+		fwrite(&zero, 1, 1, out);
+	}
+
 	// sections
 	for (uint32_t i = 0; i < assembler->sectab.len; i++) {
 		struct section *sec = &assembler->sectab.sections[i];
diff --git a/masm/asm.h b/masm/asm.h
index 81099fc..1162164 100644
--- a/masm/asm.h
+++ b/masm/asm.h
@@ -213,6 +213,7 @@ struct assembler {
 
 	/// Segments
 	struct section_table sectab;
+	uint32_t secalign; // align sections to 0x1000 when writing
 
 	/// program header
 	Elf32_Phdr *phdr;
diff --git a/masm/out.o b/masm/out.o
new file mode 100644
index 0000000000000000000000000000000000000000..0b697af7e699e823fe702ae4f22b84855c276f9f
GIT binary patch
literal 4632
zcmeHLu}T9$5Pf%vQHhwvSXfwGA!s3oNDvFb6voOTjURB5!w44x$%3XbKOkC&AK+J6
zTG|PIfp2bigAof0%NcmPv-4)>me<|8>ztiNafDe!SYjRuEx^1!3fV$}3U<gYI^F<n
zW&)t@QDeWHdEeB@IRI7GJZ5}@yaTXDUa;Wr@3LL`HB<prKow90Q~^~$6;K6K0aZX1
zPz6*0Rp1{K=;uW-Om2pwqF3R#=mW`N51oXF_ov&nPjrtOIKO|#8q7%>&)5K_CVoRx
ze1cyhSO-GMNdD5#B4)N6PBa4K7k`yVe65PhY=W^JVUS&2!{%cPq@%pB*+pveTZ^=p
z*^H&3+sBguDWtsO_P)>jz`tzr;O}0;6VEGzJY4F+%UK>OdBu4irH>)LM+o60)(Oeu
z(*F=2WPX0=3qDJ&^g&=6>=O?pM0nFC3nH8kbIhbm&}%6}=E-BW2oXFX80LXXvrOF*
PzDsXquJ48CgP(n0K=?AB

literal 0
HcmV?d00001

diff --git a/masm/test.asm b/masm/test.asm
index b4c1498..d848d29 100644
--- a/masm/test.asm
+++ b/masm/test.asm
@@ -1,3 +1,8 @@
+.rodata
+gay:
+.word 3
+
+
 .data
 
 str: