From: Yury Norov ynorov@caviumnetworks.com
maillist inclusion category: feature bugzilla: 46790 CVE: NA
Reference: https://github.com/norov/linux/commits/ilp32-5.2
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Based on Andrew Pinski's patch-series.
Signed-off-by: Yury Norov ynorov@caviumnetworks.com Signed-off-by: Yury Norov ynorov@marvell.com Signed-off-by: Xiongfeng Wang wangxiongfeng2@huawei.com Acked-by: Xie XiuQi xiexiuqi@huawei.com Signed-off-by: Chen Jun chenjun102@huawei.com Signed-off-by: Chen Jiahao chenjiahao16@huawei.com --- Documentation/arm64/ilp32.txt | 52 +++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) create mode 100644 Documentation/arm64/ilp32.txt
diff --git a/Documentation/arm64/ilp32.txt b/Documentation/arm64/ilp32.txt new file mode 100644 index 000000000000..5f01a61c92af --- /dev/null +++ b/Documentation/arm64/ilp32.txt @@ -0,0 +1,52 @@ +ILP32 AARCH64 SYSCALL ABI +========================= + +This document describes the ILP32 syscall ABI and where it differs +from the generic compat linux syscall interface. + +ILP32 is acronym for memory model which stands for "Integers, Longs and +Pointers are 32-bit". The main purpose of ILP32 in Linux kernel is providing +compatibility with 32-bit legacy code. Also, ILP32 binaries look better in some +performance tests. ARM has AN490 document which coves ILP32 details for ARM64 +platform: +http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dai0490a/ar01s01... + +AARCH64/ILP32 userspace may pass garbage in the top halve of w0-w7 registers +(syscall arguments). So top 32 bits are zeroed for them. + +Comparing to AARCH32, AARCH64/ILP32 has 64-bit length of following types: +ino_t is u64 type. +off_t is s64 type. +blkcnt_t is s64 type. +fsblkcnt_t is u64 type. +fsfilcnt_t is u64 type. +rlim_t is u64 type. + +AARCH64/ILP32 ABI uses standard syscall table which can be found at +include/uapi/asm-generic/unistd.h, with the exceptions listed below. + +Syscalls which pass 64-bit values are handled by the code shared from +AARCH32 and pass that value as a pair. Following syscalls are affected: +fadvise64_64() +fallocate() +ftruncate64() +pread64() +pwrite64() +readahead() +sync_file_range() +truncate64() + +ptrace() syscall is handled by compat version. + +shmat() syscall is handled by non-compat handler as aarch64/ilp32 has no +limitation on 4-pages alignment for shared memory. + +statfs() and fstatfs() take the size of struct statfs as an argument. +It is calculated differently in kernel and user spaces. So AARCH32 handlers +are taken to handle it. + +struct rt_sigframe is redefined and contains struct compat_siginfo, +as compat syscalls expect, and struct ilp32_ucontext, to handle +AARCH64 register set and 32-bit userspace register representation. + +elf_gregset_t is taken from lp64 to handle registers properly.