On Mon, Sep 07, 2020 at 08:57:39AM -0400, Tom Rini wrote:
On Mon, Sep 07, 2020 at 11:52:35AM +0200, Edgar E. Iglesias wrote:
On Fri, Sep 04, 2020 at 12:43:57PM -0600, Stephen Warren wrote:
On 9/4/20 3:07 AM, Edgar E. Iglesias wrote:
From: "Edgar E. Iglesias" edgar.iglesias@xilinx.com
PIE requires a 4K aligned load address. If this is not met, trap the startup sequence in a WFI loop rather than running into obscure failures.
diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S #if CONFIG_POSITION_INDEPENDENT
- /* Verify that we're 4K aligned. */
Similar to the comment on the previous patch: I believe the code that implements this check should be outside the #if check, since it's always needed.
But a check for non-PIE would have to be stricter, wouldn't it? I.e the load address needs to exactly match the link-time address.
Perhaps we should add the non-PIE check in a separate patch (if at all)?
If we can catch a bad configuration at link time in the non-PIE case (as said in another part of this thread I believe) then we should, yes, thanks!
The non-PIE configuration is expected to be loaded at a specific address. The actual load address cannot be checked at link-time (since it's up to the user at run-time) but given the assumption of a specific load-address, 4K alignment can be enforced at link-time.
It really comes down to adding reasonable run-time checks for errors that users may reasonably struggle with.
For PIE, checking for 4K aligment is reasonable because it's an easy enough misstake to make (since you've got a binary that's was supposed to handle relocation).
For non-PIE, checking for the exact address at run-time is a little bit more border-line IMO but I guess also somewhat reasonable.
There are still plenty of cases we can't catch though (loaded at odd addreses, non-RAM address-ranges etc etc).
Cheers, Edgar