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Subject[PATCHv2 2/2] extract early boot entropy from the passed cmdline
Date
From: Daniel Micay <danielmicay@gmail.com>

Existing Android bootloaders usually pass data useful as early entropy
on the kernel command-line. It may also be the case on other embedded
systems. Sample command-line from a Google Pixel running CopperheadOS:

console=ttyHSL0,115200,n8 androidboot.console=ttyHSL0
androidboot.hardware=sailfish user_debug=31 ehci-hcd.park=3
lpm_levels.sleep_disabled=1 cma=32M@0-0xffffffff buildvariant=user
veritykeyid=id:dfcb9db0089e5b3b4090a592415c28e1cb4545ab
androidboot.bootdevice=624000.ufshc androidboot.verifiedbootstate=yellow
androidboot.veritymode=enforcing androidboot.keymaster=1
androidboot.serialno=FA6CE0305299 androidboot.baseband=msm
mdss_mdp.panel=1:dsi:0:qcom,mdss_dsi_samsung_ea8064tg_1080p_cmd:1:none:cfg:single_dsi
androidboot.slot_suffix=_b fpsimd.fpsimd_settings=0
app_setting.use_app_setting=0 kernelflag=0x00000000 debugflag=0x00000000
androidboot.hardware.revision=PVT radioflag=0x00000000
radioflagex1=0x00000000 radioflagex2=0x00000000 cpumask=0x00000000
androidboot.hardware.ddr=4096MB,Hynix,LPDDR4 androidboot.ddrinfo=00000006
androidboot.ddrsize=4GB androidboot.hardware.color=GRA00
androidboot.hardware.ufs=32GB,Samsung androidboot.msm.hw_ver_id=268824801
androidboot.qf.st=2 androidboot.cid=11111111 androidboot.mid=G-2PW4100
androidboot.bootloader=8996-012001-1704121145
androidboot.oem_unlock_support=1 androidboot.fp_src=1
androidboot.htc.hrdump=detected androidboot.ramdump.opt=mem@2g:2g,mem@4g:2g
androidboot.bootreason=reboot androidboot.ramdump_enable=0 ro
root=/dev/dm-0 dm="system none ro,0 1 android-verity /dev/sda34"
rootwait skip_initramfs init=/init androidboot.wificountrycode=US
androidboot.boottime=1BLL:85,1BLE:669,2BLL:0,2BLE:1777,SW:6,KL:8136

Among other things, it contains a value unique to the device
(androidboot.serialno=FA6CE0305299), unique to the OS builds for the
device variant (veritykeyid=id:dfcb9db0089e5b3b4090a592415c28e1cb4545ab)
and timings from the bootloader stages in milliseconds
(androidboot.boottime=1BLL:85,1BLE:669,2BLL:0,2BLE:1777,SW:6,KL:8136).

Signed-off-by: Daniel Micay <danielmicay@gmail.com>
[labbott: Line-wrapped command line]
Signed-off-by: Laura Abbott <labbott@redhat.com>
---
init/main.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/init/main.c b/init/main.c
index 21d599eaad06..cb051aec46ef 100644
--- a/init/main.c
+++ b/init/main.c
@@ -533,6 +533,7 @@ asmlinkage __visible void __init start_kernel(void)
*/
add_latent_entropy();
boot_init_stack_canary();
+ add_device_randomness(command_line, strlen(command_line));
mm_init_cpumask(&init_mm);
setup_command_line(command_line);
setup_nr_cpu_ids();
--
2.13.0
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