[librm] Add support for running in 64-bit long mode
Add support for running the BIOS version of iPXE in 64-bit long mode.
A 64-bit BIOS version of iPXE can be built using e.g.
make bin-x86_64-pcbios/ipxe.usb
make bin-x86_64-pcbios/8086100e.mrom
The 64-bit BIOS version should appear to function identically to the
normal 32-bit BIOS version. The physical memory layout is unaltered:
iPXE is still relocated to the top of the available 32-bit address
space. The code is linked to a virtual address of 0xffffffffeb000000
(in the negative 2GB as required by -mcmodel=kernel), with 4kB pages
created to cover the whole of .textdata. 2MB pages are created to
cover the whole of the 32-bit address space.
The 32-bit portions of the code run with VIRTUAL_CS and VIRTUAL_DS
configured such that truncating a 64-bit virtual address gives a
32-bit virtual address pointing to the same physical location.
The stack pointer remains as a physical address when running in long
mode (although the .stack section is accessible via the negative 2GB
virtual address); this is done in order to simplify the handling of
interrupts occurring while executing a portion of 32-bit code with
flat physical addressing via PHYS_CODE().
Interrupts may be enabled in either 64-bit long mode, 32-bit protected
mode with virtual addresses, 32-bit protected mode with physical
addresses, or 16-bit real mode. Interrupts occurring in any mode
other than real mode will be reflected down to real mode and handled
by whichever ISR is hooked into the BIOS interrupt vector table.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
In a 64-bit build, the entirety of the 32-bit address space is
identity-mapped and so any valid physical address may immediately be
used as a virtual address. Conversely, a virtual address that is
already within the 32-bit address space may immediately be used as a
physical address.
A valid virtual address that lies outside the 32-bit address space
must be an address within .textdata, and so can be converted to a
physical address by adding virt_offset.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
[librm] Mark virt_offset, text16, data16, rm_cs, and rm_ds as constant
The physical locations of .textdata, .text16 and .data16 are constant
from the point of view of C code. Mark the relevant variables as
constant to allow gcc to optimise out redundant reads.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
No callers of prot_to_phys, phys_to_prot, or intr_to_prot require the
flags to be preserved. Remove the unnecessary pushfl/popfl pairs.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
[librm] Add phys_call() wrapper for calling code with physical addressing
Add a phys_call() wrapper function (analogous to the existing
real_call() wrapper function) for calling code with flat physical
addressing, and use this wrapper within the PHYS_CODE() macro.
Move the relevant functionality inside librm.S, where it more
naturally belongs.
The COMBOOT code currently uses explicit calls to _virt_to_phys and
_phys_to_virt. These will need to be rewritten if our COMBOOT support
is ever generalised to be able to run in a 64-bit build.
Specifically:
- com32_exec_loop() should be restructured to use PHYS_CODE()
- com32_wrapper.S should be restructured to use an equivalent of
prot_call(), passing parameters via a struct i386_all_regs
- there appears to be no need for com32_wrapper.S to switch between
external and internal stacks; this could be omitted to simplify
the design.
For now, librm.S continues to expose _virt_to_phys and _phys_to_virt
for use by com32.c and com32_wrapper.S. Similarly, librm.S continues
to expose _intr_to_virt for use by gdbidt.S.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
[build] Fix building on older versions of binutils
Some older versions of binutils have issues with both the use of
PROVIDE() and the interpretation of numeric literals within a section
description.
Work around these older versions by defining the required numeric
literals outside of any section description, and by automatically
determining whether or not to generate extra space for page tables
rather than relying on LDFLAGS.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The bulk of the iPXE binary (the .textdata section) is physically
relocated at runtime to the top of the 32-bit address space in order
to allow space for an OS to be loaded. The relocation is achieved
with the assistance of segmentation: we adjust the code and data
segment bases so that the link-time addresses remain valid.
Segmentation is not available (for normal code and data segments) in
long mode. We choose to compile the C code with -mcmodel=kernel and
use a link-time address of 0xffffffffeb000000. This choice allows us
to identity-map the entirety of the 32-bit address space, and to alias
our chosen link-time address to the physical location of our .textdata
section. (This requires the .textdata section to always be aligned to
a page boundary.)
We simultaneously choose to set the 32-bit virtual address segment
bases such that the link-time addresses may simply be truncated to 32
bits in order to generate a valid 32-bit virtual address. This allows
symbols in .textdata to be trivially accessed by both 32-bit and
64-bit code.
There is no (sensible) way in 32-bit assembly code to generate the
required R_X86_64_32S relocation records for these truncated symbols.
However, subtracting the fixed constant 0xffffffff00000000 has the
same effect as truncation, and can be represented in a standard
R_X86_64_32 relocation record. We define the VIRTUAL() macro to
abstract away this truncation operation, and apply it to all
references by 32-bit (or 16-bit) assembly code to any symbols within
the .textdata section.
We define "virt_offset" for a 64-bit build as "the value to be added
to an address within .textdata in order to obtain its physical
address". With this definition, the low 32 bits of "virt_offset" can
be treated by 32-bit code as functionally equivalent to "virt_offset"
in a 32-bit build.
We define "text16" and "data16" for a 64-bit build as the physical
addresses of the .text16 and .data16 sections. Since a physical
address within the 32-bit address space may be used directly as a
64-bit virtual address (thanks to the identity map), this definition
provides the most natural access to variables in .text16 and .data16.
Note that this requires a minor adjustment in prot_to_real(), which
accesses .text16 using 32-bit virtual addresses.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
[librm] Transition to protected mode within init_librm()
Long-mode operation will require page tables, which are too large to
sensibly fit in our .data16 segment in base memory.
Add a portion of init_librm() running in 32-bit protected mode to
provide access to high memory. Use this portion of init_librm() to
initialise the .textdata variables "virt_offset", "text16", and
"data16", eliminating the redundant (re)initialisation currently
performed on every mode transition as part of real_to_prot().
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Use the standard "pushl $function ; pushw %cs ; call prot_call"
sequence everywhere that prot_call() is used.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
[bios] Make uses of REAL_CODE() and PHYS_CODE() 64-bit clean
On a 64-bit CPU, any modification of a register by 32-bit or 16-bit
code will destroy the invisible upper 32 bits of the corresponding
64-bit register. For example: a 32-bit "pushl %eax" followed by a
"popl %eax" will zero the upper half of %rax. This differs from the
treatment of upper halves of 32-bit registers by 16-bit code: a
"pushw %ax" followed by a "popw %ax" will leave the upper 16 bits of
%eax unmodified.
Inline assembly generated using REAL_CODE() or PHYS_CODE() will
therefore have to preserve the upper halves of all registers, to avoid
clobbering registers that gcc expects to be preserved.
Output operands from REAL_CODE() and PHYS_CODE() assembly may
therefore contain undefined values in the upper 32 bits.
Fix by using explicit variable widths (e.g. uint32_t) for
non-discarded output operands, to ensure that undefined values in the
upper 32 bits of 64-bit registers are ignored.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Move most arch/i386 files to arch/x86, and adjust the contents of the
Makefiles and the include/bits/*.h headers to reflect the new
locations.
This patch makes no substantive code changes, as can be seen using a
rename-aware diff (e.g. "git show -M5").
This patch does not make the pcbios platform functional for x86_64; it
merely allows it to compile without errors.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
[prefix] Pad .text16 and .data16 segment sizes at build time
Commit c64747d ("[librm] Speed up real-to-protected mode transition
under KVM") rounded down the .text16 segment address calculated in
alloc_basemem() to a multiple of 64 bytes in order to speed up mode
transitions under KVM.
This creates a potential discrepancy between alloc_basemem() and
free_basemem(), meaning that free_basemem() may free less memory than
was allocated by alloc_basemem().
Fix by padding the calculated sizes of both .text16 and .data16 to a
multiple of 64 bytes at build time.
Debugged-by: Yossef Efraim <yossefe@mellanox.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
[iobuf] Improve robustness of I/O buffer allocation
Guard against various corner cases (such as zero-length buffers, zero
alignments, and integer overflow when rounding up allocation lengths
and alignments) and ensure that the struct io_buffer is correctly
aligned even when the caller requests a non-zero alignment for the I/O
buffer itself.
Add self-tests to verify that the resulting alignments and lengths are
correct for a range of allocations.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Commit f3fbb5f ("[malloc] Avoid integer overflow for excessively large
memory allocations") fixed signed integer overflow issues caused by
the use of ssize_t, but did not guard against unsigned integer
overflow.
Add explicit checks for unsigned integer overflow where needed. As a
side bonus, erroneous calls to malloc_dma() with an (illegal) size of
zero will now fail cleanly.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
ath_rx_init() demonstrates some serious confusion over how to use
pointers, resulting in (uint32_t*)NULL being used as a temporary
variable. This does not end well.
The broken code in question is performing manual alignment of I/O
buffers, which can now be achieved more simply using alloc_iob_raw().
Fix by removing ath_rxbuf_alloc() entirely.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The various early-exit paths in parse_uri() accidentally bypass the
URI field decoding. The result is that opaque or relative URIs do not
undergo URI field decoding, resulting in double-encoding when the URIs
are subsequently used. For example:
#!ipxe
set mac ${macstring}
imgfetch /boot/by-mac/${mac:uristring}
would result in an HTTP GET such as
GET /boot/by-mac/00%253A0c%253A29%253Ac5%253A39%253Aa1 HTTP/1.1
rather than the expected
GET /boot/by-mac/00%3A0c%3A29%3Ac5%3A39%3Aa1 HTTP/1.1
Fix by ensuring that URI decoding is always applied regardless of the
URI format.
Reported-by: Andrew Widdersheim <awiddersheim@inetu.net>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
TFTP URIs are intrinsically problematic, since:
- TFTP servers may use either normal slashes or backslashes as a
directory separator,
- TFTP servers allow filenames to be specified using relative paths
(with no initial directory separator),
- TFTP filenames present in a DHCP filename field may use special
characters such as "?" or "#" that prevent parsing as a generic URI.
As of commit 7667536 ("[uri] Refactor URI parsing and formatting"), we
have directly constructed TFTP URIs from DHCP next-server and filename
pairs, avoiding the generic URI parser. This eliminated the problems
related to special characters, but indirectly made it impossible to
parse a "tftp://..." URI string into a TFTP URI with a non-absolute
path.
Re-introduce the convention of requiring an extra slash in a
"tftp://..." URI string in order to specify a TFTP URI with an initial
slash in the filename. For example:
tftp://192.168.0.1/boot/pxelinux.0 => RRQ "boot/pxelinux.0"
tftp://192.168.0.1//boot/pxelinux.0 => RRQ "/boot/pxelinux.0"
This is ugly, but there seems to be no other sensible way to provide
the ability to specify all possible TFTP filenames.
A side-effect of this change is that format_uri() will no longer add a
spurious initial "/" when formatting a relative URI string. This
improves the console output when fetching an image specified via a
relative URI.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown