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[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>
pull/120/head
Michael Brown 2020-07-14 18:24:02 +01:00
parent b6eecb182e
commit 1832f8a9b0
1 changed files with 4 additions and 1 deletions
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5
src/interface/efi/efi_download.c
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@ -138,8 +138,11 @@ efi_download_start ( IPXE_DOWNLOAD_PROTOCOL *This __unused,
struct efi_download_file *file;
int rc;
efi_snp_claim();
file = malloc ( sizeof ( struct efi_download_file ) );
if ( file == NULL ) {
efi_snp_release();
return EFI_OUT_OF_RESOURCES;
}
@ -147,10 +150,10 @@ efi_download_start ( IPXE_DOWNLOAD_PROTOCOL *This __unused,
rc = xfer_open ( &file->xfer, LOCATION_URI_STRING, Url );
if ( rc ) {
free ( file );
efi_snp_release();
return EFIRC ( rc );
}
efi_snp_claim();
file->pos = 0;
file->data_callback = DataCallback;
file->finish_callback = FinishCallback;