The value of regs->orig_ax contains potentially useful debugging data: For syscalls it contains the syscall number. For interrupts it contains the (negated) vector number. To reduce noise, print it only if it has a useful value (i.e., something other than -1).
Here's what it looks like for a write syscall: RIP: 0033:[<00007f53ad7b1940>] 0x7f53ad7b1940 RSP: 002b:00007fff8de66558 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000000046 RCX: 00007f53ad7b1940 RDX: 0000000000000002 RSI: 00007f53ae0ca000 RDI: 0000000000000001 ... Suggested-by: Andy Lutomirski <[email protected]> Signed-off-by: Josh Poimboeuf <[email protected]> --- arch/x86/kernel/process_64.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 92d3f70..4481e72 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -63,8 +63,13 @@ void __show_regs(struct pt_regs *regs, int all) printk(KERN_DEFAULT "RIP: %04lx:[<%016lx>] %pS\n", regs->cs & 0xffff, regs->ip, (void *)regs->ip); - printk(KERN_DEFAULT "RSP: %04lx:%016lx EFLAGS: %08lx\n", regs->ss, + printk(KERN_DEFAULT "RSP: %04lx:%016lx EFLAGS: %08lx", regs->ss, regs->sp, regs->flags); + if (regs->orig_ax != -1) + pr_cont(" ORIG_RAX: %016lx\n", regs->orig_ax); + else + pr_cont("\n"); + printk(KERN_DEFAULT "RAX: %016lx RBX: %016lx RCX: %016lx\n", regs->ax, regs->bx, regs->cx); printk(KERN_DEFAULT "RDX: %016lx RSI: %016lx RDI: %016lx\n", -- 2.7.4
