path: root/arch/arm/kernel/traps.c
diff options
authorNicolas Pitre <nico@cam.org>2006-01-14 16:31:29 +0000
committerRussell King <rmk+kernel@arm.linux.org.uk>2006-01-14 16:31:29 +0000
commit3f2829a31573e3e502b874c8d69a765f7a778793 (patch)
tree40f64826c0d2964c56c366f770e2d3959123eb59 /arch/arm/kernel/traps.c
parentba95e4e4a0a8a3c6aba363d45f78d5f2e2d111eb (diff)
[ARM] 3105/4: ARM EABI: new syscall entry convention
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: Nicolas Pitre <nico@cam.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/kernel/traps.c')
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 93cfd3ffcc7..10235b01582 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -404,7 +404,7 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs)
struct thread_info *thread = current_thread_info();
siginfo_t info;
- if ((no >> 16) != 0x9f)
+ if ((no >> 16) != (__ARM_NR_BASE>> 16))
return bad_syscall(no, regs);
switch (no & 0xffff) {