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Michael Brown 1832f8a9b0 [efi] Claim SNP devices early in efi_download_start() 
Claiming the SNP devices has the side effect of raising the TPL to
iPXE's normal operating level of TPL_CALLBACK (see the commit message
for c89a446 ("[efi] Run at TPL_CALLBACK to protect against UEFI
timers") for details).  This must happen before executing any code
that relies upon the TPL having been raised to TPL_CALLBACK.

The call to efi_snp_claim() in efi_download_start() currently happens
only after the call to xfer_open().  Calling xfer_open() will
typically result in a retry timer being started, which will result in
a call to currticks() in order to initialise the timer.  The call to
currticks() will drop to TPL_APPLICATION and restore to TPL_CALLBACK
in order to allow a timer tick to occur.  Since this call happened
before the call to efi_snp_claim(), the restored TPL is incorrect.

This in turn results in efi_snp_claim() recording the incorrect
original TPL, causing efi_snp_release() to eventually restore the
incorrect TPL, causing the system to lock up when ExitBootServices()
is called at TPL_CALLBACK.

Fix by moving the call to efi_snp_claim() to the start of
efi_download_start().

Debugged-by: Jarrod Johnson <jjohnson2@lenovo.com>
Debugged-by: He He4 Huang <huanghe4@lenovo.com>
Debugged-by: James Wang <jameswang@ami.com.tw>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
 		2020-07-15 10:09:46 +01:00
contrib [coverity] Override assumptions about wcrtomb() and hmac_init() 2019-08-17 17:18:54 +01:00
src [efi] Claim SNP devices early in efi_download_start() 2020-07-15 10:09:46 +01:00
.travis.yml [travis] Ensure that most recent tag is always available 2020-01-03 00:14:03 +01:00
COPYING [legal] Update GPLv2 licence text 2015-02-26 17:59:53 +00:00
COPYING.GPLv2 [legal] Update GPLv2 licence text 2015-02-26 17:59:53 +00:00
COPYING.UBDL [legal] Add support for the Unmodified Binary Distribution Licence 2015-03-02 12:07:14 +00:00
README [doc] Re-add README file 2010-05-28 00:03:47 +01:00

README 

iPXE README File

Quick start guide:

   cd src
   make

For any more detailed instructions, see http://ipxe.org