diff options
Diffstat (limited to 'sys/amd64')
| -rw-r--r-- | sys/amd64/amd64/exception.S | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/sys/amd64/amd64/exception.S b/sys/amd64/amd64/exception.S index 08948c0904e0..c49547d8fa66 100644 --- a/sys/amd64/amd64/exception.S +++ b/sys/amd64/amd64/exception.S @@ -463,8 +463,16 @@ fast_syscall_common: movq PCPU(SCRATCH_RSP),%r11 /* %r11 already saved */ movq %r11,TF_RSP(%rsp) /* user stack pointer */ movq PCPU(SCRATCH_RAX),%rax + /* + * Save a few arg registers early to free them for use in + * handle_ibrs_entry(). %r10 is especially tricky. It is not an + * arg register, but it holds the arg register %rcx. Profiling + * preserves %rcx, but may clobber %r10. Profiling may also + * clobber %r11, but %r11 (original %eflags) has been saved. + */ movq %rax,TF_RAX(%rsp) /* syscall number */ movq %rdx,TF_RDX(%rsp) /* arg 3 */ + movq %r10,TF_RCX(%rsp) /* arg 4 */ SAVE_SEGS call handle_ibrs_entry movq PCPU(CURPCB),%r11 @@ -475,7 +483,6 @@ fast_syscall_common: movq $2,TF_ERR(%rsp) movq %rdi,TF_RDI(%rsp) /* arg 1 */ movq %rsi,TF_RSI(%rsp) /* arg 2 */ - movq %r10,TF_RCX(%rsp) /* arg 4 */ movq %r8,TF_R8(%rsp) /* arg 5 */ movq %r9,TF_R9(%rsp) /* arg 6 */ movq %rbx,TF_RBX(%rsp) /* C preserved */ |