ilo-pona/xv6-65oo2
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Use simple linker script to force data segment to be page aligned

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This commit is contained in:
Frans Kaashoek 2022-08-23 10:54:40 -04:00
parent cef1b57d4a
commit 4cd4d194b8
3 changed files with 43 additions and 9 deletions
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2
Makefile
View file

@ -90,7 +90,7 @@ tags: $(OBJS) _init
ULIB = $U/ulib.o $U/usys.o $U/printf.o $U/umalloc.o
_%: %.o $(ULIB)
$(LD) $(LDFLAGS) -verbose -e _main -Ttext 0 -o $@ $^
$(LD) $(LDFLAGS) -T $U/user.ld -o $@ $^
$(OBJDUMP) -S $@ > $*.asm
$(OBJDUMP) -t $@ | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > $*.sym

14
kernel/exec.c
View file

@ -7,7 +7,7 @@
#include "defs.h"
#include "elf.h"
static int loadseg(pde_t *, uint64, uint, struct inode *, uint, uint);
static int loadseg(pde_t *, uint64, struct inode *, uint, uint);
int flags2perm(int flags)
{
@ -59,15 +59,13 @@ exec(char *path, char **argv)
goto bad;
if(ph.vaddr + ph.memsz < ph.vaddr)
goto bad;
if(ph.align != PGSIZE)
if(ph.vaddr % PGSIZE != 0)
goto bad;
uint64 e = PGROUNDUP(ph.vaddr + ph.memsz);
uint64 sz1;
if((sz1 = uvmalloc(pagetable, sz, e, flags2perm(ph.flags))) == 0)
if((sz1 = uvmalloc(pagetable, sz, ph.vaddr + ph.memsz, flags2perm(ph.flags))) == 0)
goto bad;
sz = sz1;
uint64 s = PGROUNDDOWN(ph.vaddr);
if(loadseg(pagetable, s, ph.vaddr - s, ip, ph.off, ph.filesz) < 0)
if(loadseg(pagetable, ph.vaddr, ip, ph.off, ph.filesz) < 0)
goto bad;
}
iunlockput(ip);
@ -147,7 +145,7 @@ exec(char *path, char **argv)
// and the pages from va to va+sz must already be mapped.
// Returns 0 on success, -1 on failure.
static int
loadseg(pagetable_t pagetable, uint64 va, uint poff, struct inode *ip, uint offset, uint sz)
loadseg(pagetable_t pagetable, uint64 va, struct inode *ip, uint offset, uint sz)
{
uint i, n;
uint64 pa;
@ -160,7 +158,7 @@ loadseg(pagetable_t pagetable, uint64 va, uint poff, struct inode *ip, uint offs
n = sz - i;
else
n = PGSIZE;
if(readi(ip, 0, (uint64)pa+poff, offset+i, n) != n)
if(readi(ip, 0, (uint64)pa, offset+i, n) != n)
return -1;
}

36
user/user.ld Normal file
View file

@ -0,0 +1,36 @@
OUTPUT_ARCH( "riscv" )
ENTRY( _main )
SECTIONS
{
. = 0x0;
.text : {
*(.text .text.*)
}
.rodata : {
. = ALIGN(16);
*(.srodata .srodata.*) /* do not need to distinguish this from .rodata */
. = ALIGN(16);
*(.rodata .rodata.*)
. = ALIGN(0x1000);
}
.data : {
. = ALIGN(16);
*(.sdata .sdata.*) /* do not need to distinguish this from .data */
. = ALIGN(16);
*(.data .data.*)
}
.bss : {
. = ALIGN(16);
*(.sbss .sbss.*) /* do not need to distinguish this from .bss */
. = ALIGN(16);
*(.bss .bss.*)
}
PROVIDE(end = .);
}