preinit: parse rootfstype from kernel command line

This commit is contained in:
Daniel Barlow 2023-10-19 18:56:09 +01:00
parent f3225c2bd5
commit 61dc5beca8
5 changed files with 116 additions and 13 deletions

4
pkgs/preinit/Makefile Normal file
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@ -0,0 +1,4 @@
CFLAGS+=-Os -DPREINIT_USE_LIBC -fno-stack-protector -fpic -fPIC
LDFLAGS=-static
preinit: preinit.o parseopts.o

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@ -15,7 +15,6 @@ stdenv.mkDerivation {
# NIX_DEBUG=2;
hardeningDisable = [ "all" ];
CFLAGS = "-Os -static -DPREINIT_USE_LIBC -fno-stack-protector -fpic -fPIC -I ./ -I ${kernel}/tools/include/nolibc";
postBuild = ''
$STRIP --remove-section=.note --remove-section=.comment preinit

97
pkgs/preinit/parseopts.c Normal file
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@ -0,0 +1,97 @@
#include <string.h>
#include <unistd.h>
static int begins_with(char * str, char * prefix)
{
while(*prefix) {
if(*str == '\0') return 0;
if(*str != *prefix) return 0;
str++;
prefix++;
}
return 1;
}
void parseopts(char * cmdline, char **root, char **rootfstype) {
*root = 0;
*rootfstype = 0;
for(char *p = cmdline; *p; p++) {
if(begins_with(p, "root=")) {
*root = p + strlen("root=");
while(*p && (*p != ' ')) p++;
if(*p) {
*p = '\0';
p++;
};
};
if(begins_with(p, "rootfstype=")) {
*rootfstype = p + strlen("rootfstype=");
while(*p && (*p != ' ')) p++;
if(*p) {
*p = '\0';
p++;
};
};
};
}
#ifdef TESTS
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#define die(fmt, ...) do { printf(fmt, __VA_ARGS__); exit(1); } while(0)
#define S(x) #x
#define expect_equal(actual, expected) \
if(!actual || strcmp(actual, expected)) die("%d: expected \"%s\", got \"%s\"", __LINE__, expected, actual);
int main()
{
char * root = "/dev/hda1";
char * rootfstype = "xiafs";
char *buf;
// finds root= and rootfstype= options
buf = strdup("liminix console=ttyS0,115200 panic=10 oops=panic init=/bin/init loglevel=8 root=/dev/ubi0_4 rootfstype=ubifs fw_devlink=off mtdparts=phram0:18M(rootfs) phram.phram=phram0,0x40400000,18874368,65536 root=/dev/mtdblock0 foo");
parseopts(buf, &root, &rootfstype);
expect_equal(root, "/dev/mtdblock0");
expect_equal(rootfstype, "ubifs");
// in case of duplicates, chooses the latter
// also: works if the option is end of string
buf = strdup("liminix console=ttyS0,115200 panic=10 oops=panic init=/bin/init loglevel=8 root=/dev/ubi0_4 rootfstype=ubifs fw_devlink=off mtdparts=phram0:18M(rootfs) phram.phram=phram0,0x40400000,18874368,65536 root=/dev/mtdblock0");
parseopts(buf, &root, &rootfstype);
expect_equal(root, "/dev/mtdblock0");
expect_equal(rootfstype, "ubifs");
// options may appear in either order
buf = strdup("liminix fw_devlink=off root=/dev/hda1 rootfstype=ubifs foo");
parseopts(buf, &root, &rootfstype);
expect_equal(root, "/dev/hda1");
expect_equal(rootfstype, "ubifs");
buf = strdup("liminix rootfstype=ubifs fw_devlink=off root=/dev/hda1 foo");
parseopts(buf, &root, &rootfstype);
expect_equal(rootfstype, "ubifs");
expect_equal(root, "/dev/hda1");
// provides NULL for missing options
buf = strdup("liminix rufustype=ubifs fw_devlink=off foot=/dev/hda1");
parseopts(buf, &root, &rootfstype);
if(rootfstype) die("expected null rootfstype, got \"%s\"", rootfstype);
if(root) die("expected null root, got \"%s\"", root);
// provides empty strings for empty options
buf = strdup("liminix rootfstype= fw_devlink=off root= /dev/hda1");
parseopts(buf, &root, &rootfstype);
if(strlen(rootfstype)) die("expected empty rootfstype, got \"%s\"", rootfstype);
if(strlen(root)) die("expected null root, got \"%s\"", root);
}
#endif

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@ -10,6 +10,8 @@
#endif
#include <asm/setup.h>
void parseopts(char * cmdline, char **root, char **rootfstype);
#define ERR(x) write(2, x, strlen(x))
#define AVER(c) do { if(c < 0) ERR("failed: " #c); } while(0)
@ -40,6 +42,7 @@ char buf[COMMAND_LINE_SIZE];
int main(int argc, char *argv[], char *envp[])
{
char *rootdevice = 0;
char *rootfstype = 0;
char *p = buf;
write(1, banner, strlen(banner));
@ -54,22 +57,17 @@ int main(int argc, char *argv[], char *envp[])
write(1, buf, len);
};
while(*p) {
if(begins_with(p, "root=")) {
rootdevice = p + 5;
while(*p && (*p != ' ')) p++;
*p= '\0';
}
while(*p && (*p != ' ')) p++;
p++;
}
parseopts(buf, &rootdevice, &rootfstype);
if(rootdevice) {
if(!rootfstype) rootfstype = "jffs2"; /* backward compatibility */
write(1, "rootdevice ", 11);
write(1, rootdevice, strlen(rootdevice));
write(1, "\n", 1);
write(1, " (", 2);
write(1, rootfstype, strlen(rootfstype));
write(1, ")\n", 1);
AVER(mount(rootdevice, "/target/persist", "ubifs", 0, NULL));
AVER(mount(rootdevice, "/target/persist", rootfstype, 0, NULL));
AVER(mount("/target/persist/nix", "/target/nix",
"bind", MS_BIND, NULL));

5
pkgs/preinit/shell.nix Normal file
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@ -0,0 +1,5 @@
with import <nixpkgs> {};
mkShell {
name = "preinit-env";
src = ./.;
}