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Implement kvm_write() for dump files. We map the file privately so that 

changes don't get propagated back, and then write to the private buffer.
This is not useful yes, but it is simple enough to make pread use the buffer
if it is available.
This commit is contained in:
christos 2020-04-28 00:12:01 +00:00
parent 77c1bb7123
commit 39cda3989e
2 changed files with 66 additions and 6 deletions
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68
lib/libkvm/kvm.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: kvm.c,v 1.105 2020/03/08 00:06:42 chs Exp $ */
/* $NetBSD: kvm.c,v 1.106 2020/04/28 00:12:01 christos Exp $ */
/*-
* Copyright (c) 1989, 1992, 1993
@ -38,7 +38,7 @@
#if 0
static char sccsid[] = "@(#)kvm.c 8.2 (Berkeley) 2/13/94";
#else
__RCSID("$NetBSD: kvm.c,v 1.105 2020/03/08 00:06:42 chs Exp $");
__RCSID("$NetBSD: kvm.c,v 1.106 2020/04/28 00:12:01 christos Exp $");
#endif
#endif /* LIBC_SCCS and not lint */
@ -48,6 +48,7 @@ __RCSID("$NetBSD: kvm.c,v 1.105 2020/03/08 00:06:42 chs Exp $");
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/mman.h>
#include <sys/core.h>
#include <sys/exec.h>
@ -205,6 +206,19 @@ _kvm_pread(kvm_t *kd, int fd, void *buf, size_t size, off_t off)
return size;
}
static ssize_t
_kvm_pwrite(kvm_t *kd, const void *buf, size_t size, off_t off)
{
char *mem = kd->dump_mem;
if (size + off > kd->dump_size) {
errno = EINVAL;
return -1;
}
memcpy(mem + off, buf, size);
return size;
}
/*
* Wrapper around the pread(2) system call; calls _kvm_syserr() for us
* in the event of emergency.
@ -256,6 +270,8 @@ _kvm_open(kvm_t *kd, const char *uf, const char *mf, const char *sf, int flag,
kd->iobuf = NULL;
kd->iobufsz = 0;
kd->errbuf[0] = '\0';
kd->dump_mem = MAP_FAILED;
kd->dump_size = 0;
if (flag & KVM_NO_FILES) {
kd->alive = KVM_ALIVE_SYSCTL;
@ -371,6 +387,11 @@ _kvm_open(kvm_t *kd, const char *uf, const char *mf, const char *sf, int flag,
if (_kvm_initvtop(kd) < 0)
goto failed;
}
kd->dump_size = (size_t)st.st_size;
kd->dump_mem = mmap(NULL, kd->dump_size, PROT_READ|PROT_WRITE,
MAP_FILE|MAP_PRIVATE, kd->pmfd, 0);
if (kd->dump_mem == MAP_FAILED)
goto failed;
}
return (kd);
failed:
@ -758,6 +779,8 @@ kvm_close(kvm_t *kd)
free(kd->argv);
if (kd->iobuf != 0)
free(kd->iobuf);
if (kd->dump_mem != MAP_FAILED)
munmap(kd->dump_mem, kd->dump_size);
free(kd);
return (error);
@ -891,6 +914,7 @@ ssize_t
kvm_write(kvm_t *kd, u_long kva, const void *buf, size_t len)
{
int cc;
const void *cp;
if (ISKMEM(kd)) {
/*
@ -909,9 +933,43 @@ kvm_write(kvm_t *kd, u_long kva, const void *buf, size_t len)
"can't use kvm_write");
return (-1);
} else {
_kvm_err(kd, kd->program,
"kvm_write not implemented for dead kernels");
return (-1);
if (kd->dump_mem == MAP_FAILED) {
_kvm_err(kd, kd->program,
"kvm_write not implemented for dead kernels");
return (-1);
}
cp = buf;
while (len > 0) {
paddr_t pa;
off_t foff;
cc = _kvm_kvatop(kd, (vaddr_t)kva, &pa);
if (cc == 0) {
_kvm_err(kd, kd->program, "_kvm_kvatop(%lx)", kva);
return (-1);
}
if (cc > len)
cc = len;
foff = _kvm_pa2off(kd, pa);
errno = 0;
cc = _kvm_pwrite(kd, cp, (size_t)cc, foff);
if (cc < 0) {
_kvm_syserr(kd, kd->program, "kvm_pwrite");
break;
}
/*
* If kvm_kvatop returns a bogus value or our core
* file is truncated, we might wind up seeking beyond
* the end of the core file in which case the read will
* return 0 (EOF).
*/
if (cc == 0)
break;
cp = (const char *)cp + cc;
kva += cc;
len -= cc;
}
return ((const char *)cp - (const char *)buf);
}
/* NOTREACHED */
}

4
lib/libkvm/kvm_private.h
View File

@ -1,4 +1,4 @@
/* $NetBSD: kvm_private.h,v 1.20 2011/09/12 21:11:32 christos Exp $ */
/* $NetBSD: kvm_private.h,v 1.21 2020/04/28 00:12:01 christos Exp $ */
/*-
* Copyright (c) 1992, 1993
@ -72,6 +72,8 @@ struct __kvm {
size_t cpu_dsize;
void *cpu_data;
off_t dump_off; /* Where the actual dump starts */
void *dump_mem;
size_t dump_size;
/*
* Kernel virtual address translation state. This only gets filled