tree f08508537c062b3307544b678238a5c247ca33cb
parent 3d3dca077ae298636f441b302264abe7a1af7b9f
author Alexandru Elisei <alexandru.elisei@arm.com> 1634045106 +0100
committer Will Deacon <will@kernel.org> 1634110619 +0100

pci: Fix pci_dev_* print macros

Evaluate the "pci_hdr" argument before attempting to deference a field.
This fixes cryptic errors like this one, which came about during a
debugging session:

vfio/pci.c: In function 'vfio_pci_bar_activate':
include/kvm/pci.h:18:40: error: invalid type argument of '->' (have 'struct pci_device_header')
  pr_warning("[%04x:%04x] " fmt, pci_hdr->vendor_id, pci_hdr->device_id, ##__VA_ARGS__)
                                        ^~
vfio/pci.c:482:3: note: in expansion of macro 'pci_dev_warn'
   pci_dev_warn(&vdev->pci.hdr, "%s: BAR4\n", __func__);

This is caused by the operator precedence rules in C, where pointer
deference via "->" has a higher precedence than taking the address with the
ampersand symbol. When the macro is substituted, it becomes
&vdev->pci.hdr->vendor_id and it dereferences vdev->pci.hdr, which is not a
pointer, instead of dereferencing &vdev->pci.hdr, which is a pointer, and
quite likely what the author intended.

Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Link: https://lore.kernel.org/r/20211012132510.42134-4-alexandru.elisei@arm.com
Signed-off-by: Will Deacon <will@kernel.org>