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kernel: add find and replace bootargs hack
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Add find and replace bootargs to device tree cmdline hack. Now we can
find and replace bootargs by setting bootargs-find-1, bootargs-replace-1,
bootargs-exact-match-1 and bootargs-find-2, bootargs-replace-2,
bootargs-exact-match-2 under the chosen node in the device tree.

The purpose of thie hack is to to add support for Linksys MX4300,
a dual firmware device. This device's default kernel command lines
aren't compatiailbe with OpenWrt's UBI, so we leverage find and
replace to dynamically patch the cmd.

Signed-off-by: Qiyuan Zhang <[email protected]>
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@asd333111
asd333111 authored and Qiyuan Zhang committed Aug 3, 2024
1 parent d42bf52 commit 5a5dd45
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Showing 2 changed files with 96 additions and 3 deletions.
86 changes: 83 additions & 3 deletions target/linux/generic/hack-6.6/920-device_tree_cmdline.patch
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Original file line number Diff line number Diff line change
Expand Up @@ -9,13 +9,93 @@ Subject: [PATCH] of/ftd: add device tree cmdline

--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -1185,6 +1185,9 @@ int __init early_init_dt_scan_chosen(cha
p = of_get_flat_dt_prop(node, "bootargs", &l);
@@ -1157,6 +1157,17 @@ int __init early_init_dt_scan_chosen(cha
const void *rng_seed;
const void *fdt = initial_boot_params;

+ int i, cmd_len, f_len, r_len;
+ const char *exact_match;
+ char *s_ptr, *l_end, *r_end, *cur_ptr, *end_ptr;
+ int offset, step;
+
+ const int bootargs_replace_num = 2;
+ const char *bootargs_replace_nodes[2][3] =
+ { {"bootargs-find-1", "bootargs-replace-1", "bootargs-exact-match-1"},
+ {"bootargs-find-2", "bootargs-replace-2", "bootargs-exact-match-2"} };
+
+
node = fdt_path_offset(fdt, "/chosen");
if (node < 0)
node = fdt_path_offset(fdt, "/chosen@0");
@@ -1186,6 +1197,71 @@ int __init early_init_dt_scan_chosen(cha
if (p != NULL && l > 0)
strscpy(cmdline, p, min(l, COMMAND_LINE_SIZE));

+ for(i = 0; i < bootargs_replace_num; i++) {
+ p = of_get_flat_dt_prop(node, bootargs_replace_nodes[i][0], &f_len);
+ if (p == NULL || f_len == 0 )
+ continue;
+
+ exact_match = of_get_flat_dt_prop(node, bootargs_replace_nodes[i][2], &l);
+
+ if (exact_match != NULL && l > 0 && exact_match[0] == 'y') {
+ if(strncmp(cmdline, p, r_len) == 0)
+ s_ptr = cmdline;
+ else
+ s_ptr = NULL;
+ } else {
+ s_ptr = strstr(cmdline, p);
+ }
+
+ if(!s_ptr)
+ continue;
+
+ p = of_get_flat_dt_prop(node, bootargs_replace_nodes[i][1], &r_len);
+
+ if (p == NULL || f_len == 0)
+ continue;
+
+ pr_info("Input kernel commad line: %s\n", cmdline);
+
+ cmd_len = strlen(cmdline);
+
+ if (cmd_len - f_len + r_len < COMMAND_LINE_SIZE) {
+
+ pr_info("Replace kernel command line with %s\n", bootargs_replace_nodes[i][1]);
+
+ offset = r_len - f_len;
+
+ if (offset != 0) {
+ l_end = s_ptr + f_len - 1;
+ r_end = cmdline + cmd_len;
+
+ if (offset > 0) {
+ step = -1;
+ cur_ptr = r_end;
+ end_ptr = l_end + step;
+ } else {
+ step = 1;
+ cur_ptr = l_end;
+ end_ptr = r_end + step;
+ }
+
+ for (; cur_ptr != end_ptr; cur_ptr += step) {
+ *(cur_ptr + offset) = *cur_ptr;
+ }
+ }
+
+ strncpy(s_ptr, p, r_len - 1);
+
+ pr_info("Kernel command line after replacement: %s\n", cmdline);
+ } else {
+ pr_err("Replace kernel command line with %s failed\n", bootargs_replace_nodes[i][1]);
+ }
+ }
+
+ p = of_get_flat_dt_prop(node, "bootargs-append", &l);
+ if (p != NULL && l > 0)
+ strlcat(cmdline, p, min_t(int, strlen(cmdline) + (int)l, COMMAND_LINE_SIZE));
+
handle_cmdline:
/*
* CONFIG_CMDLINE is meant to be a default in case nothing else
13 changes: 13 additions & 0 deletions target/linux/qualcommax/files/arch/arm64/boot/dts/qcom/ipq8174-mx4300.dts
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,19 @@
/ {
model = "Linksys MX4300";
compatible = "linksys,mx4300", "qcom,ipq8074";

chosen {
bootargs-append = "";

// Replace the bootargs from u-boot with find and replace
bootargs-find-1 = "init=/sbin/init rootfstype=squashfs ubi.mtd=22,2048 ubi.block=0,0 root=/dev/ubiblock0_0 rootwait ro";
bootargs-exact-match-1 = "y";
bootargs-replace-1 = "rootfstype=squashfs ubi.mtd=22,4096 ubi.block=0,0 root=/dev/ubiblock0_0 rootwait ro";

bootargs-find-2 = "init=/sbin/init rootfstype=squashfs ubi.mtd=24,2048 ubi.block=0,0 root=/dev/ubiblock0_0 rootwait ro";
bootargs-exact-match-2 = "y";
bootargs-replace-2 = "rootfstype=squashfs ubi.mtd=24,4096 ubi.block=0,0 root=/dev/ubiblock0_0 rootwait ro";
};
};

&qpic_nand {
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