On 5 September 2017 at 20:37, Tony Lindgren [off-list ref] wrote:

* Ard Biesheuvel [off-list ref] [170905 09:49]:

quoted

On 5 September 2017 at 17:45, Tony Lindgren [off-list ref] wrote:

quoted

I did see boot attempts fail with randomize enable where no output
was produced. It seems this is happening for me maybe 1 out of 5 boots.
Enabling DEBUG_LL did not show anything either.

Yes. I am looking into a couple of kernelci boot reports that look
suspicious, but it is rather difficult to reproduce, for obvious
reasons :-)

Which hardware are you testing this on?

For testing on omap3, I'm mostly using logicpd torpedo devkit as
it works out of box with PM with mainline Linux and has NFSroot
usable too.

Right. Well, I will try to reproduce with the BB white I have.

Are you booting with an initrd?

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Then loading modules with CONFIG_RANDOMIZE_BASE=y seems to fail with:

$ sudo modprobe rtc-twl
rtc_twl: disagrees about version of symbol module_layout
modprobe: ERROR: could not insert 'rtc_twl': Exec format error

Is this with CONFIG_MODVERSIONS enabled?

Yes, but disabling that did not seem to make any difference
based on just one test.

Yeah, well, it appears I missed a couple of details :-)

This should fix the module loading issues:

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 1a0304dd388d..bbefd5f32ec2 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig

@@ -1830,6 +1830,8 @@ config RANDOMIZE_BASE
  depends on MMU && AUTO_ZRELADDR
  depends on !XIP_KERNEL && !ZBOOT_ROM
  select RELOCATABLE
+ select ARM_MODULE_PLTS if MODULES
+ select MODULE_REL_CRCS if MODVERSIONS
  help
   Randomizes the virtual and physical address at which the kernel
   image is loaded, as a security feature that deters exploit attempts

diff --git a/arch/arm/include/asm/elf.h b/arch/arm/include/asm/elf.h
index f13ae153fb24..b56fc4dd27b6 100644
--- a/arch/arm/include/asm/elf.h
+++ b/arch/arm/include/asm/elf.h

@@ -50,6 +50,7 @@ typedef struct user_fp elf_fpregset_t;
 #define R_ARM_NONE 0
 #define R_ARM_PC24 1
 #define R_ARM_ABS32 2
+#define R_ARM_REL32 3
 #define R_ARM_CALL 28
 #define R_ARM_JUMP24 29
 #define R_ARM_TARGET1 38

diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
index 3ff571c2c71c..aa4d72837cd5 100644
--- a/arch/arm/kernel/module.c
+++ b/arch/arm/kernel/module.c

@@ -175,6 +175,10 @@
  *(u32 *)loc |= offset & 0x7fffffff;
  break;

+ case R_ARM_REL32:
+ *(u32 *)loc += sym->st_value - loc;
+ break;
+
  case R_ARM_MOVW_ABS_NC:
  case R_ARM_MOVT_ABS:
  offset = tmp = __mem_to_opcode_arm(*(u32 *)loc);