diff options
| -rw-r--r-- | gdb/ChangeLog | 19 | ||||
| -rw-r--r-- | gdb/config/i386/tm-linux.h | 1 | ||||
| -rw-r--r-- | gdb/i386-linux-nat.c | 246 | ||||
| -rw-r--r-- | gdb/i386-tdep.c | 257 |
4 files changed, 265 insertions, 258 deletions
diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 7703083..2be3fab 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,22 @@ +2000-03-16 Jim Blandy <jimb@redhat.com> + + * i386-tdep.c (LINUX_SIGTRAMP_INSN0, LINUX_SIGTRAMP_OFFSET0, + LINUX_SIGTRAMP_INSN1, LINUX_SIGTRAMP_OFFSET1, + LINUX_SIGTRAMP_INSN2, LINUX_SIGTRAMP_OFFSET2, linux_sigtramp_code, + LINUX_SIGTRAMP_LEN, i386_linux_sigtramp_start, + LINUX_RT_SIGTRAMP_INSN0, LINUX_RT_SIGTRAMP_OFFSET0, + LINUX_RT_SIGTRAMP_INSN1, LINUX_RT_SIGTRAMP_OFFSET1, + linux_rt_sigtramp_code, LINUX_RT_SIGTRAMP_LEN, + i386_linux_rt_sigtramp_start, i386_linux_in_sigtramp, + i386_linux_sigcontext_addr, LINUX_SIGCONTEXT_PC_OFFSET, + i386_linux_sigtramp_saved_pc, LINUX_SIGCONTEXT_SP_OFFSET, + i386_linux_sigtramp_saved_sp): Deleted. These all implement + Linux-specific signal trampoline detection, and should be moved to... + * i386-linux-nat.c: ... here. + * config/i386/tm-linux.h (I386_LINUX_SIGTRAMP): No need to define + this any more, since we're not enabling OS-specific code in a + OS-independent file. + 2000-03-16 Eli Zaretskii <eliz@is.elta.co.il> * Makefile.in (go32-nat.o): Add prerequisites. diff --git a/gdb/config/i386/tm-linux.h b/gdb/config/i386/tm-linux.h index 3c557f0..c6d8dde 100644 --- a/gdb/config/i386/tm-linux.h +++ b/gdb/config/i386/tm-linux.h @@ -98,7 +98,6 @@ extern int i387_store_floating (PTR addr, int len, long double val); are used to identify this bit of code as a signal trampoline in order to support backtracing through calls to signal handlers. */ -#define I386_LINUX_SIGTRAMP #define IN_SIGTRAMP(pc, name) i386_linux_in_sigtramp (pc, name) extern int i386_linux_in_sigtramp (CORE_ADDR, char *); diff --git a/gdb/i386-linux-nat.c b/gdb/i386-linux-nat.c index 3239801..ca87ffd 100644 --- a/gdb/i386-linux-nat.c +++ b/gdb/i386-linux-nat.c @@ -1042,6 +1042,252 @@ i386_linux_skip_solib_resolver (CORE_ADDR pc) } +/* Recognizing signal handler frames. */ + +/* Linux has two flavors of signals. Normal signal handlers, and + "realtime" (RT) signals. The RT signals can provide additional + information to the signal handler if the SA_SIGINFO flag is set + when establishing a signal handler using `sigaction'. It is not + unlikely that future versions of Linux will support SA_SIGINFO for + normal signals too. */ + +/* When the i386 Linux kernel calls a signal handler and the + SA_RESTORER flag isn't set, the return address points to a bit of + code on the stack. This function returns whether the PC appears to + be within this bit of code. + + The instruction sequence for normal signals is + pop %eax + mov $0x77,%eax + int $0x80 + or 0x58 0xb8 0x77 0x00 0x00 0x00 0xcd 0x80. + + Checking for the code sequence should be somewhat reliable, because + the effect is to call the system call sigreturn. This is unlikely + to occur anywhere other than a signal trampoline. + + It kind of sucks that we have to read memory from the process in + order to identify a signal trampoline, but there doesn't seem to be + any other way. The IN_SIGTRAMP macro in tm-linux.h arranges to + only call us if no function name could be identified, which should + be the case since the code is on the stack. + + Detection of signal trampolines for handlers that set the + SA_RESTORER flag is in general not possible. Unfortunately this is + what the GNU C Library has been doing for quite some time now. + However, as of version 2.1.2, the GNU C Library uses signal + trampolines (named __restore and __restore_rt) that are identical + to the ones used by the kernel. Therefore, these trampolines are + supported too. */ + +#define LINUX_SIGTRAMP_INSN0 (0x58) /* pop %eax */ +#define LINUX_SIGTRAMP_OFFSET0 (0) +#define LINUX_SIGTRAMP_INSN1 (0xb8) /* mov $NNNN,%eax */ +#define LINUX_SIGTRAMP_OFFSET1 (1) +#define LINUX_SIGTRAMP_INSN2 (0xcd) /* int */ +#define LINUX_SIGTRAMP_OFFSET2 (6) + +static const unsigned char linux_sigtramp_code[] = +{ + LINUX_SIGTRAMP_INSN0, /* pop %eax */ + LINUX_SIGTRAMP_INSN1, 0x77, 0x00, 0x00, 0x00, /* mov $0x77,%eax */ + LINUX_SIGTRAMP_INSN2, 0x80 /* int $0x80 */ +}; + +#define LINUX_SIGTRAMP_LEN (sizeof linux_sigtramp_code) + +/* If PC is in a sigtramp routine, return the address of the start of + the routine. Otherwise, return 0. */ + +static CORE_ADDR +i386_linux_sigtramp_start (CORE_ADDR pc) +{ + unsigned char buf[LINUX_SIGTRAMP_LEN]; + + /* We only recognize a signal trampoline if PC is at the start of + one of the three instructions. We optimize for finding the PC at + the start, as will be the case when the trampoline is not the + first frame on the stack. We assume that in the case where the + PC is not at the start of the instruction sequence, there will be + a few trailing readable bytes on the stack. */ + + if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0) + return 0; + + if (buf[0] != LINUX_SIGTRAMP_INSN0) + { + int adjust; + + switch (buf[0]) + { + case LINUX_SIGTRAMP_INSN1: + adjust = LINUX_SIGTRAMP_OFFSET1; + break; + case LINUX_SIGTRAMP_INSN2: + adjust = LINUX_SIGTRAMP_OFFSET2; + break; + default: + return 0; + } + + pc -= adjust; + + if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0) + return 0; + } + + if (memcmp (buf, linux_sigtramp_code, LINUX_SIGTRAMP_LEN) != 0) + return 0; + + return pc; +} + +/* This function does the same for RT signals. Here the instruction + sequence is + mov $0xad,%eax + int $0x80 + or 0xb8 0xad 0x00 0x00 0x00 0xcd 0x80. + + The effect is to call the system call rt_sigreturn. */ + +#define LINUX_RT_SIGTRAMP_INSN0 (0xb8) /* mov $NNNN,%eax */ +#define LINUX_RT_SIGTRAMP_OFFSET0 (0) +#define LINUX_RT_SIGTRAMP_INSN1 (0xcd) /* int */ +#define LINUX_RT_SIGTRAMP_OFFSET1 (5) + +static const unsigned char linux_rt_sigtramp_code[] = +{ + LINUX_RT_SIGTRAMP_INSN0, 0xad, 0x00, 0x00, 0x00, /* mov $0xad,%eax */ + LINUX_RT_SIGTRAMP_INSN1, 0x80 /* int $0x80 */ +}; + +#define LINUX_RT_SIGTRAMP_LEN (sizeof linux_rt_sigtramp_code) + +/* If PC is in a RT sigtramp routine, return the address of the start + of the routine. Otherwise, return 0. */ + +static CORE_ADDR +i386_linux_rt_sigtramp_start (CORE_ADDR pc) +{ + unsigned char buf[LINUX_RT_SIGTRAMP_LEN]; + + /* We only recognize a signal trampoline if PC is at the start of + one of the two instructions. We optimize for finding the PC at + the start, as will be the case when the trampoline is not the + first frame on the stack. We assume that in the case where the + PC is not at the start of the instruction sequence, there will be + a few trailing readable bytes on the stack. */ + + if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0) + return 0; + + if (buf[0] != LINUX_RT_SIGTRAMP_INSN0) + { + if (buf[0] != LINUX_RT_SIGTRAMP_INSN1) + return 0; + + pc -= LINUX_RT_SIGTRAMP_OFFSET1; + + if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0) + return 0; + } + + if (memcmp (buf, linux_rt_sigtramp_code, LINUX_RT_SIGTRAMP_LEN) != 0) + return 0; + + return pc; +} + +/* Return whether PC is in a Linux sigtramp routine. */ + +int +i386_linux_in_sigtramp (CORE_ADDR pc, char *name) +{ + if (name) + return STREQ ("__restore", name) || STREQ ("__restore_rt", name); + + return (i386_linux_sigtramp_start (pc) != 0 + || i386_linux_rt_sigtramp_start (pc) != 0); +} + +/* Assuming FRAME is for a Linux sigtramp routine, return the address + of the associated sigcontext structure. */ + +CORE_ADDR +i386_linux_sigcontext_addr (struct frame_info *frame) +{ + CORE_ADDR pc; + + pc = i386_linux_sigtramp_start (frame->pc); + if (pc) + { + CORE_ADDR sp; + + if (frame->next) + /* If this isn't the top frame, the next frame must be for the + signal handler itself. The sigcontext structure lives on + the stack, right after the signum argument. */ + return frame->next->frame + 12; + + /* This is the top frame. We'll have to find the address of the + sigcontext structure by looking at the stack pointer. Keep + in mind that the first instruction of the sigtramp code is + "pop %eax". If the PC is at this instruction, adjust the + returned value accordingly. */ + sp = read_register (SP_REGNUM); + if (pc == frame->pc) + return sp + 4; + return sp; + } + + pc = i386_linux_rt_sigtramp_start (frame->pc); + if (pc) + { + if (frame->next) + /* If this isn't the top frame, the next frame must be for the + signal handler itself. The sigcontext structure is part of + the user context. A pointer to the user context is passed + as the third argument to the signal handler. */ + return read_memory_integer (frame->next->frame + 16, 4) + 20; + + /* This is the top frame. Again, use the stack pointer to find + the address of the sigcontext structure. */ + return read_memory_integer (read_register (SP_REGNUM) + 8, 4) + 20; + } + + error ("Couldn't recognize signal trampoline."); + return 0; +} + +/* Offset to saved PC in sigcontext, from <asm/sigcontext.h>. */ +#define LINUX_SIGCONTEXT_PC_OFFSET (56) + +/* Assuming FRAME is for a Linux sigtramp routine, return the saved + program counter. */ + +CORE_ADDR +i386_linux_sigtramp_saved_pc (struct frame_info *frame) +{ + CORE_ADDR addr; + addr = i386_linux_sigcontext_addr (frame); + return read_memory_integer (addr + LINUX_SIGCONTEXT_PC_OFFSET, 4); +} + +/* Offset to saved SP in sigcontext, from <asm/sigcontext.h>. */ +#define LINUX_SIGCONTEXT_SP_OFFSET (28) + +/* Assuming FRAME is for a Linux sigtramp routine, return the saved + stack pointer. */ + +CORE_ADDR +i386_linux_sigtramp_saved_sp (struct frame_info *frame) +{ + CORE_ADDR addr; + addr = i386_linux_sigcontext_addr (frame); + return read_memory_integer (addr + LINUX_SIGCONTEXT_SP_OFFSET, 4); +} + + /* Register that we are able to handle Linux ELF core file formats. */ static struct core_fns linux_elf_core_fns = diff --git a/gdb/i386-tdep.c b/gdb/i386-tdep.c index e940e2f..2420ec1 100644 --- a/gdb/i386-tdep.c +++ b/gdb/i386-tdep.c @@ -779,263 +779,6 @@ i386v4_sigtramp_saved_pc (frame) } #endif /* I386V4_SIGTRAMP_SAVED_PC */ -#ifdef I386_LINUX_SIGTRAMP - -/* Linux has two flavors of signals. Normal signal handlers, and - "realtime" (RT) signals. The RT signals can provide additional - information to the signal handler if the SA_SIGINFO flag is set - when establishing a signal handler using `sigaction'. It is not - unlikely that future versions of Linux will support SA_SIGINFO for - normal signals too. */ - -/* When the i386 Linux kernel calls a signal handler and the - SA_RESTORER flag isn't set, the return address points to a bit of - code on the stack. This function returns whether the PC appears to - be within this bit of code. - - The instruction sequence for normal signals is - pop %eax - mov $0x77,%eax - int $0x80 - or 0x58 0xb8 0x77 0x00 0x00 0x00 0xcd 0x80. - - Checking for the code sequence should be somewhat reliable, because - the effect is to call the system call sigreturn. This is unlikely - to occur anywhere other than a signal trampoline. - - It kind of sucks that we have to read memory from the process in - order to identify a signal trampoline, but there doesn't seem to be - any other way. The IN_SIGTRAMP macro in tm-linux.h arranges to - only call us if no function name could be identified, which should - be the case since the code is on the stack. - - Detection of signal trampolines for handlers that set the - SA_RESTORER flag is in general not possible. Unfortunately this is - what the GNU C Library has been doing for quite some time now. - However, as of version 2.1.2, the GNU C Library uses signal - trampolines (named __restore and __restore_rt) that are identical - to the ones used by the kernel. Therefore, these trampolines are - supported too. */ - -#define LINUX_SIGTRAMP_INSN0 (0x58) /* pop %eax */ -#define LINUX_SIGTRAMP_OFFSET0 (0) -#define LINUX_SIGTRAMP_INSN1 (0xb8) /* mov $NNNN,%eax */ -#define LINUX_SIGTRAMP_OFFSET1 (1) -#define LINUX_SIGTRAMP_INSN2 (0xcd) /* int */ -#define LINUX_SIGTRAMP_OFFSET2 (6) - -static const unsigned char linux_sigtramp_code[] = -{ - LINUX_SIGTRAMP_INSN0, /* pop %eax */ - LINUX_SIGTRAMP_INSN1, 0x77, 0x00, 0x00, 0x00, /* mov $0x77,%eax */ - LINUX_SIGTRAMP_INSN2, 0x80 /* int $0x80 */ -}; - -#define LINUX_SIGTRAMP_LEN (sizeof linux_sigtramp_code) - -/* If PC is in a sigtramp routine, return the address of the start of - the routine. Otherwise, return 0. */ - -static CORE_ADDR -i386_linux_sigtramp_start (CORE_ADDR pc) -{ - unsigned char buf[LINUX_SIGTRAMP_LEN]; - - /* We only recognize a signal trampoline if PC is at the start of - one of the three instructions. We optimize for finding the PC at - the start, as will be the case when the trampoline is not the - first frame on the stack. We assume that in the case where the - PC is not at the start of the instruction sequence, there will be - a few trailing readable bytes on the stack. */ - - if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0) - return 0; - - if (buf[0] != LINUX_SIGTRAMP_INSN0) - { - int adjust; - - switch (buf[0]) - { - case LINUX_SIGTRAMP_INSN1: - adjust = LINUX_SIGTRAMP_OFFSET1; - break; - case LINUX_SIGTRAMP_INSN2: - adjust = LINUX_SIGTRAMP_OFFSET2; - break; - default: - return 0; - } - - pc -= adjust; - - if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0) - return 0; - } - - if (memcmp (buf, linux_sigtramp_code, LINUX_SIGTRAMP_LEN) != 0) - return 0; - - return pc; -} - -/* This function does the same for RT signals. Here the instruction - sequence is - mov $0xad,%eax - int $0x80 - or 0xb8 0xad 0x00 0x00 0x00 0xcd 0x80. - - The effect is to call the system call rt_sigreturn. */ - -#define LINUX_RT_SIGTRAMP_INSN0 (0xb8) /* mov $NNNN,%eax */ -#define LINUX_RT_SIGTRAMP_OFFSET0 (0) -#define LINUX_RT_SIGTRAMP_INSN1 (0xcd) /* int */ -#define LINUX_RT_SIGTRAMP_OFFSET1 (5) - -static const unsigned char linux_rt_sigtramp_code[] = -{ - LINUX_RT_SIGTRAMP_INSN0, 0xad, 0x00, 0x00, 0x00, /* mov $0xad,%eax */ - LINUX_RT_SIGTRAMP_INSN1, 0x80 /* int $0x80 */ -}; - -#define LINUX_RT_SIGTRAMP_LEN (sizeof linux_rt_sigtramp_code) - -/* If PC is in a RT sigtramp routine, return the address of the start - of the routine. Otherwise, return 0. */ - -static CORE_ADDR -i386_linux_rt_sigtramp_start (CORE_ADDR pc) -{ - unsigned char buf[LINUX_RT_SIGTRAMP_LEN]; - - /* We only recognize a signal trampoline if PC is at the start of - one of the two instructions. We optimize for finding the PC at - the start, as will be the case when the trampoline is not the - first frame on the stack. We assume that in the case where the - PC is not at the start of the instruction sequence, there will be - a few trailing readable bytes on the stack. */ - - if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0) - return 0; - - if (buf[0] != LINUX_RT_SIGTRAMP_INSN0) - { - if (buf[0] != LINUX_RT_SIGTRAMP_INSN1) - return 0; - - pc -= LINUX_RT_SIGTRAMP_OFFSET1; - - if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0) - return 0; - } - - if (memcmp (buf, linux_rt_sigtramp_code, LINUX_RT_SIGTRAMP_LEN) != 0) - return 0; - - return pc; -} - -/* Return whether PC is in a Linux sigtramp routine. */ - -int -i386_linux_in_sigtramp (CORE_ADDR pc, char *name) -{ - if (name) - return STREQ ("__restore", name) || STREQ ("__restore_rt", name); - - return (i386_linux_sigtramp_start (pc) != 0 - || i386_linux_rt_sigtramp_start (pc) != 0); -} - -/* Assuming FRAME is for a Linux sigtramp routine, return the address - of the associated sigcontext structure. */ - -CORE_ADDR -i386_linux_sigcontext_addr (struct frame_info *frame) -{ - CORE_ADDR pc; - - pc = i386_linux_sigtramp_start (frame->pc); - if (pc) - { - CORE_ADDR sp; - - if (frame->next) - /* If this isn't the top frame, the next frame must be for the - signal handler itself. The sigcontext structure lives on - the stack, right after the signum argument. */ - return frame->next->frame + 12; - - /* This is the top frame. We'll have to find the address of the - sigcontext structure by looking at the stack pointer. Keep - in mind that the first instruction of the sigtramp code is - "pop %eax". If the PC is at this instruction, adjust the - returned value accordingly. */ - sp = read_register (SP_REGNUM); - if (pc == frame->pc) - return sp + 4; - return sp; - } - - pc = i386_linux_rt_sigtramp_start (frame->pc); - if (pc) - { - if (frame->next) - /* If this isn't the top frame, the next frame must be for the - signal handler itself. The sigcontext structure is part of - the user context. A pointer to the user context is passed - as the third argument to the signal handler. */ - return read_memory_integer (frame->next->frame + 16, 4) + 20; - - /* This is the top frame. Again, use the stack pointer to find - the address of the sigcontext structure. */ - return read_memory_integer (read_register (SP_REGNUM) + 8, 4) + 20; - } - - error ("Couldn't recognize signal trampoline."); - return 0; -} - -/* Offset to saved PC in sigcontext, from <asm/sigcontext.h>. */ -#define LINUX_SIGCONTEXT_PC_OFFSET (56) - -/* Assuming FRAME is for a Linux sigtramp routine, return the saved - program counter. */ - -CORE_ADDR -i386_linux_sigtramp_saved_pc (struct frame_info *frame) -{ - CORE_ADDR addr; - addr = i386_linux_sigcontext_addr (frame); - return read_memory_integer (addr + LINUX_SIGCONTEXT_PC_OFFSET, 4); -} - -/* Offset to saved SP in sigcontext, from <asm/sigcontext.h>. */ -#define LINUX_SIGCONTEXT_SP_OFFSET (28) - -/* Assuming FRAME is for a Linux sigtramp routine, return the saved - stack pointer. */ - -CORE_ADDR -i386_linux_sigtramp_saved_sp (struct frame_info *frame) -{ - CORE_ADDR addr; - addr = i386_linux_sigcontext_addr (frame); - return read_memory_integer (addr + LINUX_SIGCONTEXT_SP_OFFSET, 4); -} - -/* Immediately after a function call, return the saved pc. */ - -CORE_ADDR -i386_linux_saved_pc_after_call (struct frame_info *frame) -{ - if (frame->signal_handler_caller) - return i386_linux_sigtramp_saved_pc (frame); - - return read_memory_integer (read_register (SP_REGNUM), 4); -} - -#endif /* I386_LINUX_SIGTRAMP */ #ifdef STATIC_TRANSFORM_NAME /* SunPRO encodes the static variables. This is not related to C++ mangling, |