diff options
Diffstat (limited to 'gdb')
| -rw-r--r-- | gdb/ChangeLog | 6 | ||||
| -rw-r--r-- | gdb/config/i386/nm-linux.h | 3 | ||||
| -rw-r--r-- | gdb/i386-linux-nat.c | 85 |
3 files changed, 94 insertions, 0 deletions
diff --git a/gdb/ChangeLog b/gdb/ChangeLog index ddbf754..463d9c1 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,9 @@ +2000-04-30 Mark Kettenis <kettenis@gnu.org> + + Fix single-stepping out of signal trampolines. + * config/i386/nm-linux.h (CHILD_RESUME): Define. + * i386-linux-nat.c (child_resume): New function. + Fri Apr 28 16:22:34 2000 Andrew Cagney <cagney@b1.cygnus.com> * blockframe.c (frameless_look_for_prologue): Use diff --git a/gdb/config/i386/nm-linux.h b/gdb/config/i386/nm-linux.h index 1095fa0..4fb6965 100644 --- a/gdb/config/i386/nm-linux.h +++ b/gdb/config/i386/nm-linux.h @@ -72,6 +72,9 @@ extern int kernel_u_size PARAMS ((void)); #define CANNOT_FETCH_REGISTER(regno) ((regno) >= NUM_GREGS) #define CANNOT_STORE_REGISTER(regno) CANNOT_FETCH_REGISTER (regno) +/* Override child_resume in `infptrace.c'. */ +#define CHILD_RESUME + extern CORE_ADDR i386_stopped_by_watchpoint PARAMS ((int)); extern int diff --git a/gdb/i386-linux-nat.c b/gdb/i386-linux-nat.c index 93ea241..2bfac29 100644 --- a/gdb/i386-linux-nat.c +++ b/gdb/i386-linux-nat.c @@ -951,6 +951,91 @@ fetch_core_registers (char *core_reg_sect, unsigned core_reg_size, } +/* The instruction for a Linux system call is: + int $0x80 + or 0xcd 0x80. */ + +static const unsigned char linux_syscall[] = { 0xcd, 0x80 }; + +#define LINUX_SYSCALL_LEN (sizeof linux_syscall) + +/* The system call number is stored in the %eax register. */ +#define LINUX_SYSCALL_REGNUM 0 /* %eax */ + +/* We are specifically interested in the sigreturn and rt_sigreturn + system calls. */ + +#ifndef SYS_sigreturn +#define SYS_sigreturn 0x77 +#endif +#ifndef SYS_rt_sigreturn +#define SYS_rt_sigreturn 0xad +#endif + +/* Offset to saved processor flags, from <asm/sigcontext.h>. */ +#define LINUX_SIGCONTEXT_EFLAGS_OFFSET (64) + +/* Resume execution of the inferior process. + If STEP is nonzero, single-step it. + If SIGNAL is nonzero, give it that signal. */ + +void +child_resume (int pid, int step, enum target_signal signal) +{ + int request = PTRACE_CONT; + + if (pid == -1) + /* Resume all threads. */ + /* I think this only gets used in the non-threaded case, where "resume + all threads" and "resume inferior_pid" are the same. */ + pid = inferior_pid; + + if (step) + { + CORE_ADDR pc = read_pc_pid (pid); + unsigned char buf[LINUX_SYSCALL_LEN]; + + request = PTRACE_SINGLESTEP; + + /* Returning from a signal trampoline is done by calling a + special system call (sigreturn or rt_sigreturn, see + i386-linux-tdep.c for more information). This system call + restores the registers that were saved when the signal was + raised, including %eflags. That means that single-stepping + won't work. Instead, we'll have to modify the signal context + that's about to be restored, and set the trace flag there. */ + + /* First check if PC is at a system call. */ + if (read_memory_nobpt (pc, (char *) buf, LINUX_SYSCALL_LEN) == 0 + && memcmp (buf, linux_syscall, LINUX_SYSCALL_LEN) == 0) + { + int syscall = read_register_pid (LINUX_SYSCALL_REGNUM, pid); + + /* Then check the system call number. */ + if (syscall == SYS_sigreturn || syscall == SYS_rt_sigreturn) + { + CORE_ADDR sp = read_register (SP_REGNUM); + CORE_ADDR addr = sp; + unsigned long int eflags; + + if (syscall == SYS_rt_sigreturn) + addr = read_memory_integer (sp + 8, 4) + 20; + + /* Set the trace flag in the context that's about to be + restored. */ + addr += LINUX_SIGCONTEXT_EFLAGS_OFFSET; + read_memory (addr, (char *) &eflags, 4); + eflags |= 0x0100; + write_memory (addr, (char *) &eflags, 4); + } + } + } + + if (ptrace (request, pid, 0, target_signal_to_host (signal)) == -1) + perror_with_name ("ptrace"); +} + + /* Calling functions in shared libraries. */ /* FIXME: kettenis/2000-03-05: Doesn't this belong in a target-dependent file? The function |