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  1. 14 Jan, 2006 5 commits
    • Nicolas Pitre's avatar
      [ARM] 3105/4: ARM EABI: new syscall entry convention · 3f2829a3
      Nicolas Pitre authored 
      Patch from Nicolas Pitre

For a while we wanted to change the way syscalls were called on ARM.
Instead of encoding the syscall number in the swi instruction which
requires reading back the instruction from memory to extract that number
and polluting the data cache, it was decided that simply storing the
syscall number into r7 would be more efficient. Since this represents
an ABI change then making that change at the same time as EABI support
is the right thing to do.

It is now expected that EABI user space binaries put the syscall number
into r7 and use "swi 0" to call the kernel. Syscall register argument
are also expected to have "EABI arrangement" i.e. 64-bit arguments
should be put in a pair of registers from an even register number.

Example with long ftruncate64(unsigned int fd, loff_t length):

	legacy ABI:
	- put fd into r0
	- put length into r1-r2
	- use "swi #(0x900000 + 194)" to call the kernel

	new ARM EABI:
	- put fd into r0
	- put length into r2-r3 (skipping over r1)
	- put 194 into r7
	- use "swi 0" to call the kernel

Note that it is important to use 0 for the swi argument as backward
compatibility with legacy ABI user space relies on this.
The syscall macros in asm-arm/unistd.h were also updated to support
both ABIs and implement the right call method automatically.
Signed-off-by: default avatarNicolas Pitre <nico@cam.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
      3f2829a3
    • Nicolas Pitre's avatar
      [ARM] 3104/1: ARM EABI: new helper function names · ba95e4e4
      Nicolas Pitre authored 
      Patch from Nicolas Pitre

The ARM EABI defines new names for GCC helper functions.
Signed-off-by: default avatarNicolas Pitre <nico@cam.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
      ba95e4e4
    • Nicolas Pitre's avatar
      [ARM] 3103/1: ARM EABI: stack pointer must be 64-bit aligned (part 2) · 499b2ea1
      Nicolas Pitre authored 
      Patch from Nicolas Pitre

We must make sure that assembly code that modifies the stack pointer
before calling a C function does it so it remains 64-bit aligned.
Signed-off-by: default avatarNicolas Pitre <nico@cam.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
      499b2ea1
    • Nicolas Pitre's avatar
      [ARM] 3102/1: ARM EABI: stack pointer must be 64-bit aligned after a CPU exception · 2dede2d8
      Nicolas Pitre authored 
      Patch from Nicolas Pitre

The ARM EABI says that the stack pointer has to be 64-bit aligned for
reasons already mentioned in patch #3101 when calling C functions.

We therefore must verify and adjust sp accordingly when taking an
exception from kernel mode since sp might not necessarily be 64-bit
aligned if the exception occurs in the middle of a kernel function.

If the exception occurs while in user mode then no sp fixup is needed as
long as sizeof(struct pt_regs) as well as any additional syscall data
stack space remain multiples of 8.
Signed-off-by: default avatarNicolas Pitre <nico@cam.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
      2dede2d8
    • Nicolas Pitre's avatar
      [ARM] 3101/1: ARM EABI: slab memory must be 64-bit aligned · da2b1cd6
      Nicolas Pitre authored 
      Patch from Nicolas Pitre

Although ARM is still using 32-bit pointers, version 5 and later
versions of the ARM architecture introduced the ldrd and strd
instructions to move 64-bit data which must be 64-bit aligned in memory,
and the EABI includes new constraints on structure data alignment to
allow for the compiler to use those instructions. This means that any
slab allocation must start on a 64-bit boundary which is not equivalent
to BYTES_PER_WORD, especially on those architecture versions that
implements the ldrd/strd instructions.

Overriding the default alignment disables some slab debug features. If
those debug features are really needed then the kernel will have to be
compiled for version 4 of the ARM architecture.
Signed-off-by: default avatarNicolas Pitre <nico@cam.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
      da2b1cd6
  3. 13 Jan, 2006 8 commits
  5. 12 Jan, 2006 27 commits