From: Roland McGrath <roland@redhat.com> Using kgdb-ga.patch from -mm, if userland single-steps (PTRACE_SINGLESTEP) into the `sysenter' instruction, kgdb reports a bogus trap: Program received signal SIGTRAP, Trace/breakpoint trap. sysenter_past_esp () at arch/i386/kernel/entry.S:249 1: x/i $pc 0xc0106023 <sysenter_past_esp>: sti (gdb) The hackery in the "FIX_STACK" macro in entry.S changes the saved PC for a the spurious kernel-mode debug trap when TF was set on user-mode execution of `sysenter', so sysenter_past_esp is where it actually lies in this case. The following patch removes the kgdb hiccup when userland PTRACE_SINGLESTEP's into sysenter. Signed-off-by: Andrew Morton <akpm@osdl.org> --- 25-akpm/arch/i386/kernel/entry.S | 1 + 25-akpm/arch/i386/kernel/traps.c | 4 ++-- 2 files changed, 3 insertions(+), 2 deletions(-) diff -puN arch/i386/kernel/entry.S~kgdb-gapatch-fix-for-i386-single-step-into-sysenter arch/i386/kernel/entry.S --- 25/arch/i386/kernel/entry.S~kgdb-gapatch-fix-for-i386-single-step-into-sysenter 2004-06-23 23:34:52.508730784 -0700 +++ 25-akpm/arch/i386/kernel/entry.S 2004-06-23 23:34:52.513730024 -0700 @@ -245,6 +245,7 @@ need_resched: # sysenter call handler stub ENTRY(sysenter_entry) movl TSS_sysenter_esp0(%esp),%esp + .globl sysenter_past_esp sysenter_past_esp: sti pushl $(__USER_DS) diff -puN arch/i386/kernel/traps.c~kgdb-gapatch-fix-for-i386-single-step-into-sysenter arch/i386/kernel/traps.c --- 25/arch/i386/kernel/traps.c~kgdb-gapatch-fix-for-i386-single-step-into-sysenter 2004-06-23 23:34:52.509730632 -0700 +++ 25-akpm/arch/i386/kernel/traps.c 2004-06-23 23:34:52.514729872 -0700 @@ -103,7 +103,7 @@ static int valid_stack_ptr(struct task_s } #ifdef CONFIG_KGDB -extern void sysenter_entry(void); +extern void sysenter_past_esp(void); #include <asm/kgdb.h> #include <linux/init.h> void set_intr_gate(unsigned int n, void *addr); @@ -667,7 +667,7 @@ asmlinkage void do_debug(struct pt_regs * that really belongs to user space. Others are * "Ours all ours!" */ - if (((regs->xcs & 3) == 0) && ((void *)regs->eip == sysenter_entry)) + if (((regs->xcs & 3) == 0) && ((void *)regs->eip == sysenter_past_esp)) goto clear_TF_reenable; #else if ((regs->xcs & 3) == 0) _