From: "Steven Rostedt (Red Hat)" Currently save_mcount_regs is passed a "skip" parameter to know how much stack updated the pt_regs, as it tries to keep the saved pt_regs in the same location for all users. This is rather stupid, especially since the part stored on the pt_regs has nothing to do with what is suppose to be in that location. Instead of doing that, just pass in an "added" parameter that lets that macro know how much stack was added before it was called so that it can get to the RIP. But the difference is that it will now offset the pt_regs by that "added" count. The caller now needs to take care of the offset of the pt_regs. This will make it easier to simplify the code later. Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1411262304010.3961@nanos Reviewed-by: Thomas Gleixner Signed-off-by: Steven Rostedt --- arch/x86/kernel/mcount_64.S | 37 ++++++++++++++++++------------------- 1 file changed, 18 insertions(+), 19 deletions(-) diff --git a/arch/x86/kernel/mcount_64.S b/arch/x86/kernel/mcount_64.S index 4f1b27642495..596ac330c1db 100644 --- a/arch/x86/kernel/mcount_64.S +++ b/arch/x86/kernel/mcount_64.S @@ -37,12 +37,12 @@ * be saved in the locations that pt_regs has them in. */ -/* skip is set if the stack was already partially adjusted */ -.macro save_mcount_regs skip=0 +/* @added: the amount of stack added before calling this */ +.macro save_mcount_regs added=0 /* * We add enough stack to save all regs. */ - subq $(SS+8-\skip), %rsp + subq $(SS+8), %rsp movq %rax, RAX(%rsp) movq %rcx, RCX(%rsp) movq %rdx, RDX(%rsp) @@ -51,11 +51,11 @@ movq %r8, R8(%rsp) movq %r9, R9(%rsp) /* Move RIP to its proper location */ - movq SS+8(%rsp), %rdi + movq SS+8+\added(%rsp), %rdi movq %rdi, RIP(%rsp) .endm -.macro restore_mcount_regs skip=0 +.macro restore_mcount_regs movq R9(%rsp), %r9 movq R8(%rsp), %r8 movq RDI(%rsp), %rdi @@ -63,12 +63,12 @@ movq RDX(%rsp), %rdx movq RCX(%rsp), %rcx movq RAX(%rsp), %rax - addq $(SS+8-\skip), %rsp + addq $(SS+8), %rsp .endm /* skip is set if stack has been adjusted */ -.macro ftrace_caller_setup trace_label skip=0 - save_mcount_regs \skip +.macro ftrace_caller_setup trace_label added=0 + save_mcount_regs \added /* Save this location */ GLOBAL(\trace_label) @@ -79,9 +79,9 @@ GLOBAL(\trace_label) subq $MCOUNT_INSN_SIZE, %rdi /* Load the parent_ip into the second parameter */ #ifdef CC_USING_FENTRY - movq SS+16(%rsp), %rsi + movq SS+16+\added(%rsp), %rsi #else - movq 8(%rbp), %rsi + movq 8+\added(%rbp), %rsi #endif .endm @@ -156,10 +156,10 @@ GLOBAL(ftrace_stub) END(ftrace_caller) ENTRY(ftrace_regs_caller) - /* Save the current flags before compare (in SS location)*/ + /* Save the current flags before any operations that can change them */ pushfq - /* skip=8 to skip flags saved in SS */ + /* added 8 bytes to save flags */ ftrace_caller_setup ftrace_regs_caller_op_ptr 8 /* Save the rest of pt_regs */ @@ -172,15 +172,15 @@ ENTRY(ftrace_regs_caller) movq %rbp, RBP(%rsp) movq %rbx, RBX(%rsp) /* Copy saved flags */ - movq SS(%rsp), %rcx + movq SS+8(%rsp), %rcx movq %rcx, EFLAGS(%rsp) /* Kernel segments */ movq $__KERNEL_DS, %rcx movq %rcx, SS(%rsp) movq $__KERNEL_CS, %rcx movq %rcx, CS(%rsp) - /* Stack - skipping return address */ - leaq SS+16(%rsp), %rcx + /* Stack - skipping return address and flags */ + leaq SS+8*3(%rsp), %rcx movq %rcx, RSP(%rsp) /* regs go into 4th parameter */ @@ -195,11 +195,11 @@ GLOBAL(ftrace_regs_call) /* Copy flags back to SS, to restore them */ movq EFLAGS(%rsp), %rax - movq %rax, SS(%rsp) + movq %rax, SS+8(%rsp) /* Handlers can change the RIP */ movq RIP(%rsp), %rax - movq %rax, SS+8(%rsp) + movq %rax, SS+8*2(%rsp) /* restore the rest of pt_regs */ movq R15(%rsp), %r15 @@ -210,8 +210,7 @@ GLOBAL(ftrace_regs_call) movq RBP(%rsp), %rbp movq RBX(%rsp), %rbx - /* skip=8 to skip flags saved in SS */ - restore_mcount_regs 8 + restore_mcount_regs /* Restore flags */ popfq -- 2.1.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/