On 2024/01/05 16:30, Aditya Gupta wrote: Nit: depending on terminal environment, this looks broken. Could you redraw this with ascii chars? for example, | | crash_target <--------+--| ---------+->| | | Thanks, Kazu > > Implement `machdep->get_cpu_reg` on PPC64, so that crash provides the > register values to gdb to unwind stack frames properly > > With these changes, on powerpc, 'bt' command output in gdb mode, will look > like this: > > gdb> bt > #0 0xc0000000002a53e8 in crash_setup_regs (oldregs=<optimized out>, newregs=0xc00000000486f8d8) at ./arch/powerpc/include/asm/kexec.h:69 > #1 __crash_kexec (regs=<optimized out>) at kernel/kexec_core.c:974 > #2 0xc000000000168918 in panic (fmt=<optimized out>) at kernel/panic.c:358 > #3 0xc000000000b735f8 in sysrq_handle_crash (key=<optimized out>) at drivers/tty/sysrq.c:155 > #4 0xc000000000b742cc in __handle_sysrq (key=key@entry=99, check_mask=check_mask@entry=false) at drivers/tty/sysrq.c:602 > #5 0xc000000000b7506c in write_sysrq_trigger (file=<optimized out>, buf=<optimized out>, count=2, ppos=<optimized out>) at drivers/tty/sysrq.c:1163 > #6 0xc00000000069a7bc in pde_write (ppos=<optimized out>, count=<optimized out>, buf=<optimized out>, file=<optimized out>, pde=0xc000000009ed3a80) at fs/proc/inode.c:340 > #7 proc_reg_write (file=<optimized out>, buf=<optimized out>, count=<optimized out>, ppos=<optimized out>) at fs/proc/inode.c:352 > #8 0xc0000000005b3bbc in vfs_write (file=file@entry=0xc00000009dda7d00, buf=buf@entry=0xebcfc7c6040 <error: Cannot access memory at address 0xebcfc7c6040>, count=count@entry=2, pos=pos@entry=0xc00000000486fda0) at fs/read_write.c:582 > > instead of earlier output without this patch: > > gdb> bt > #0 <unavailable> in ?? () > Backtrace stopped: previous frame identical to this frame (corrupt stack?) > > Also, 'get_dumpfile_regs' has been introduced to get registers from > multiple supported vmcore formats. Correspondingly a flag 'BT_NO_PRINT_REGS' > has been introduced to tell helper functions to get registers, to not > print registers with every call to backtrace in gdb. > > Note: This feature to support GDB unwinding doesn't support live debugging > > Signed-off-by: Aditya Gupta <adityag(a)linux.ibm.com&gt; > --- > defs.h | 122 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ > kernel.c | 33 +++++++++++++++ > ppc64.c | 105 +++++++++++++++++++++++++++++++++++++++++++++-- > 3 files changed, 257 insertions(+), 3 deletions(-) > > diff --git a/defs.h b/defs.h > index 5218a94fe4a4..615f3a37935a 100644 > --- a/defs.h > +++ b/defs.h > @@ -6023,6 +6023,7 @@ int load_module_symbols_helper(char *); > void unlink_module(struct load_module *); > int check_specified_module_tree(char *, char *); > int is_system_call(char *, ulong); > +void get_dumpfile_regs(struct bt_info*, ulong*, ulong*); > void generic_dump_irq(int); > void generic_get_irq_affinity(int); > void generic_show_interrupts(int, ulong *); > @@ -6121,6 +6122,7 @@ ulong cpu_map_addr(const char *type); > #define BT_REGS_NOT_FOUND (0x4000000000000ULL) > #define BT_OVERFLOW_STACK (0x8000000000000ULL) > #define BT_SKIP_IDLE (0x10000000000000ULL) > +#define BT_NO_PRINT_REGS (0x20000000000000ULL) > #define BT_SYMBOL_OFFSET (BT_SYMBOLIC_ARGS) > > #define BT_REF_HEXVAL (0x1) > @@ -7854,4 +7856,124 @@ enum x86_64_regnum { > LAST_REGNUM > }; > > +/* > + * Register numbers to make crash_target->fetch_registers() > + * ---> machdep->get_cpu_reg() work properly. > + * > + * These register numbers and names are given according to output of > + * `rs6000_register_name`, because that is what was being used by > + * crash_target::fetch_registers in case of PPC64 > + */ > +enum ppc64_regnum { > + PPC64_R0_REGNUM = 0, > + PPC64_R1_REGNUM, > + PPC64_R2_REGNUM, > + PPC64_R3_REGNUM, > + PPC64_R4_REGNUM, > + PPC64_R5_REGNUM, > + PPC64_R6_REGNUM, > + PPC64_R7_REGNUM, > + PPC64_R8_REGNUM, > + PPC64_R9_REGNUM, > + PPC64_R10_REGNUM, > + PPC64_R11_REGNUM, > + PPC64_R12_REGNUM, > + PPC64_R13_REGNUM, > + PPC64_R14_REGNUM, > + PPC64_R15_REGNUM, > + PPC64_R16_REGNUM, > + PPC64_R17_REGNUM, > + PPC64_R18_REGNUM, > + PPC64_R19_REGNUM, > + PPC64_R20_REGNUM, > + PPC64_R21_REGNUM, > + PPC64_R22_REGNUM, > + PPC64_R23_REGNUM, > + PPC64_R24_REGNUM, > + PPC64_R25_REGNUM, > + PPC64_R26_REGNUM, > + PPC64_R27_REGNUM, > + PPC64_R28_REGNUM, > + PPC64_R29_REGNUM, > + PPC64_R30_REGNUM, > + PPC64_R31_REGNUM, > + > + PPC64_F0_REGNUM = 32, > + PPC64_F1_REGNUM, > + PPC64_F2_REGNUM, > + PPC64_F3_REGNUM, > + PPC64_F4_REGNUM, > + PPC64_F5_REGNUM, > + PPC64_F6_REGNUM, > + PPC64_F7_REGNUM, > + PPC64_F8_REGNUM, > + PPC64_F9_REGNUM, > + PPC64_F10_REGNUM, > + PPC64_F11_REGNUM, > + PPC64_F12_REGNUM, > + PPC64_F13_REGNUM, > + PPC64_F14_REGNUM, > + PPC64_F15_REGNUM, > + PPC64_F16_REGNUM, > + PPC64_F17_REGNUM, > + PPC64_F18_REGNUM, > + PPC64_F19_REGNUM, > + PPC64_F20_REGNUM, > + PPC64_F21_REGNUM, > + PPC64_F22_REGNUM, > + PPC64_F23_REGNUM, > + PPC64_F24_REGNUM, > + PPC64_F25_REGNUM, > + PPC64_F26_REGNUM, > + PPC64_F27_REGNUM, > + PPC64_F28_REGNUM, > + PPC64_F29_REGNUM, > + PPC64_F30_REGNUM, > + PPC64_F31_REGNUM, > + > + PPC64_PC_REGNUM = 64, > + PPC64_MSR_REGNUM = 65, > + PPC64_CR_REGNUM = 66, > + PPC64_LR_REGNUM = 67, > + PPC64_CTR_REGNUM = 68, > + PPC64_XER_REGNUM = 69, > + PPC64_FPSCR_REGNUM = 70, > + > + PPC64_VR0_REGNUM = 106, > + PPC64_VR1_REGNUM, > + PPC64_VR2_REGNUM, > + PPC64_VR3_REGNUM, > + PPC64_VR4_REGNUM, > + PPC64_VR5_REGNUM, > + PPC64_VR6_REGNUM, > + PPC64_VR7_REGNUM, > + PPC64_VR8_REGNUM, > + PPC64_VR9_REGNUM, > + PPC64_VR10_REGNUM, > + PPC64_VR11_REGNUM, > + PPC64_VR12_REGNUM, > + PPC64_VR13_REGNUM, > + PPC64_VR14_REGNUM, > + PPC64_VR15_REGNUM, > + PPC64_VR16_REGNUM, > + PPC64_VR17_REGNUM, > + PPC64_VR18_REGNUM, > + PPC64_VR19_REGNUM, > + PPC64_VR20_REGNUM, > + PPC64_VR21_REGNUM, > + PPC64_VR22_REGNUM, > + PPC64_VR23_REGNUM, > + PPC64_VR24_REGNUM, > + PPC64_VR25_REGNUM, > + PPC64_VR26_REGNUM, > + PPC64_VR27_REGNUM, > + PPC64_VR28_REGNUM, > + PPC64_VR29_REGNUM, > + PPC64_VR30_REGNUM, > + PPC64_VR31_REGNUM, > + > + PPC64_VSCR_REGNUM = 138, > + PPC64_VRSAVE_REGNU = 139 > +}; > + > #endif /* !GDB_COMMON */ > diff --git a/kernel.c b/kernel.c > index 6dcf414693e6..52b7ba09f390 100644 > --- a/kernel.c > +++ b/kernel.c > @@ -3533,6 +3533,39 @@ get_lkcd_regs(struct bt_info *bt, ulong *eip, ulong *esp) > machdep->get_stack_frame(bt, eip, esp); > } > > +void > +get_dumpfile_regs(struct bt_info *bt, ulong *eip, ulong *esp) > +{ > + bt->flags |= BT_NO_PRINT_REGS; > + > + if (NETDUMP_DUMPFILE()) > + get_netdump_regs(bt, eip, esp); > + else if (KDUMP_DUMPFILE()) > + get_kdump_regs(bt, eip, esp); > + else if (DISKDUMP_DUMPFILE()) > + get_diskdump_regs(bt, eip, esp); > + else if (KVMDUMP_DUMPFILE()) > + get_kvmdump_regs(bt, eip, esp); > + else if (LKCD_DUMPFILE()) > + get_lkcd_regs(bt, eip, esp); > + else if (XENDUMP_DUMPFILE()) > + get_xendump_regs(bt, eip, esp); > + else if (SADUMP_DUMPFILE()) > + get_sadump_regs(bt, eip, esp); > + else if (VMSS_DUMPFILE()) > + get_vmware_vmss_regs(bt, eip, esp); > + else if (REMOTE_PAUSED()) { > + if (!is_task_active(bt->task) || !get_remote_regs(bt, eip, esp)) > + machdep->get_stack_frame(bt, eip, esp); > + } else > + machdep->get_stack_frame(bt, eip, esp); > + > + bt->flags &= ~BT_NO_PRINT_REGS; > + > + bt->instptr = *eip; > + bt->stkptr = *esp; > +} > + > > /* > * Store the head of the kernel module list for future use. > diff --git a/ppc64.c b/ppc64.c > index e8930a139e0d..ea4821d86b9e 100644 > --- a/ppc64.c > +++ b/ppc64.c > @@ -55,6 +55,8 @@ static void ppc64_set_bt_emergency_stack(enum emergency_stack_type type, > static char * ppc64_check_eframe(struct ppc64_pt_regs *); > static void ppc64_print_eframe(char *, struct ppc64_pt_regs *, > struct bt_info *); > +static int ppc64_get_cpu_reg(int cpu, int regno, const char *name, int size, > + void *value); > static void parse_cmdline_args(void); > static int ppc64_paca_percpu_offset_init(int); > static void ppc64_init_cpu_info(void); > @@ -704,6 +706,8 @@ ppc64_init(int when) > error(FATAL, "cannot malloc hwirqstack buffer space."); > } > > + machdep->get_cpu_reg = ppc64_get_cpu_reg; > + > ppc64_init_paca_info(); > > if (!machdep->hz) { > @@ -2501,6 +2505,99 @@ ppc64_print_eframe(char *efrm_str, struct ppc64_pt_regs *regs, > ppc64_print_nip_lr(regs, 1); > } > > +static int > +ppc64_get_cpu_reg(int cpu, int regno, const char *name, int size, > + void *value) > +{ > + struct bt_info bt_info, bt_setup; > + struct task_context *tc; > + struct ppc64_pt_regs *pt_regs; > + ulong ip, sp; > + > + if (LIVE()) { > + /* doesn't support reading registers in live dump */ > + return FALSE; > + } > + > + /* Currently only handling registers available in ppc64_pt_regs: > + * > + * 0-31: r0-r31 > + * 64: pc/nip > + * 65: msr > + * > + * 67: lr > + * 68: ctr > + */ > + switch (regno) { > + case PPC64_R0_REGNUM ... PPC64_R31_REGNUM: > + > + case PPC64_PC_REGNUM: > + case PPC64_MSR_REGNUM: > + case PPC64_LR_REGNUM: > + case PPC64_CTR_REGNUM: > + break; > + > + default: > + // return false if we can't get that register > + if (CRASHDEBUG(1)) > + error(WARNING, "unsupported register, regno=%d\n", regno); > + return FALSE; > + } > + > + tc = CURRENT_CONTEXT(); > + BZERO(&bt_setup, sizeof(struct bt_info)); > + clone_bt_info(&bt_setup, &bt_info, tc); > + fill_stackbuf(&bt_info); > + > + // reusing the get_dumpfile_regs function to get pt regs structure > + get_dumpfile_regs(&bt_info, &sp, &ip); > + pt_regs = (struct ppc64_pt_regs *)bt_info.machdep; > + > + if (!pt_regs) { > + error(WARNING, "pt_regs not available for cpu %d\n", cpu); > + return FALSE; > + } > + > + switch (regno) { > + case PPC64_R0_REGNUM ... PPC64_R31_REGNUM: > + if (size != sizeof(pt_regs->gpr[regno])) > + return FALSE; // size mismatch > + > + memcpy(value, &pt_regs->gpr[regno], size); > + break; > + > + case PPC64_PC_REGNUM: > + if (size != sizeof(pt_regs->nip)) > + return FALSE; // size mismatch > + > + memcpy(value, &pt_regs->nip, size); > + break; > + > + case PPC64_MSR_REGNUM: > + if (size != sizeof(pt_regs->msr)) > + return FALSE; // size mismatch > + > + memcpy(value, &pt_regs->msr, size); > + break; > + > + case PPC64_LR_REGNUM: > + if (size != sizeof(pt_regs->link)) > + return FALSE; // size mismatch > + > + memcpy(value, &pt_regs->link, size); > + break; > + > + case PPC64_CTR_REGNUM: > + if (size != sizeof(pt_regs->ctr)) > + return FALSE; // size mismatch > + > + memcpy(value, &pt_regs->ctr, size); > + break; > + } > + > + return TRUE; > +} > + > /* > * For vmcore typically saved with KDump or FADump, get SP and IP values > * from the saved ptregs. > @@ -2613,9 +2710,11 @@ ppc64_get_dumpfile_stack_frame(struct bt_info *bt_in, ulong *nip, ulong *ksp) > pt_regs = (struct ppc64_pt_regs *)bt->machdep; > ur_nip = pt_regs->nip; > ur_ksp = pt_regs->gpr[1]; > - /* Print the collected regs for panic task. */ > - ppc64_print_regs(pt_regs); > - ppc64_print_nip_lr(pt_regs, 1); > + if (!(bt->flags & BT_NO_PRINT_REGS)) { > + /* Print the collected regs for panic task. */ > + ppc64_print_regs(pt_regs); > + ppc64_print_nip_lr(pt_regs, 1); > + } > } else if ((pc->flags & KDUMP) || > ((pc->flags & DISKDUMP) && > (*diskdump_flags & KDUMP_CMPRS_LOCAL))) {

Currently, 'frame' is prohibited on every architecture, even in gdb mode. Since the passthrough is working on few architectures (eg. ppc64, and vmss x86_64), so remove it from prohibited list, so that 'frame' command can be used This has an implication on all architectures, that 'frame' now outputs this in default mode: ``` crash> frame #0 <unavailable> in ?? () ``` instead of the before prohibited message ``` crash> frame crash: prohibited gdb command: frame ``` Though, 'frame' should work in gdb mode for architectures that implement 'machdep->get_cpu_reg' Signed-off-by: Aditya Gupta <adityag(a)linux.ibm.com&gt; --- gdb_interface.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/gdb_interface.c b/gdb_interface.c index b14319c66147..8f99a0d7fd54 100644 --- a/gdb_interface.c +++ b/gdb_interface.c @@ -711,7 +711,7 @@ static char *prohibited_list[] = { "watch", "rwatch", "awatch", "attach", "continue", "c", "fg", "detach", "finish", "handle", "interrupt", "jump", "kill", "next", "nexti", "signal", "step", "s", "stepi", "target", "until", "delete", - "clear", "disable", "enable", "condition", "ignore", "frame", "catch", + "clear", "disable", "enable", "condition", "ignore", "catch", "tcatch", "return", "file", "exec-file", "core-file", "symbol-file", "load", "si", "ni", "shell", "sy", NULL /* must be last */ -- 2.43.0

On 2024/01/05 16:30, Aditya Gupta wrote: Please move this hunk to the end of gdb-10.2.patch. Thanks, Kazu > --- gdb-10.2/gdb/symfile.c.orig > +++ gdb-10.2/gdb/symfile.c > @@ -652,7 +652,26 @@ default_symfile_offsets (struct objfile *objfile, > diff --git a/kernel.c b/kernel.c > index 52b7ba09f390..a8d60507dd95 100644 > --- a/kernel.c > +++ b/kernel.c > @@ -6504,7 +6504,13 @@ set_cpu(int cpu) > if (hide_offline_cpu(cpu)) > error(FATAL, "invalid cpu number: cpu %d is OFFLINE\n", cpu); > > - if ((task = get_active_task(cpu))) > + task = get_active_task(cpu); > + > + /* Check if context is already set to given cpu */ > + if (task == CURRENT_TASK()) > + return; > + > + if (task) > set_context(task, NO_PID); > else > error(FATAL, "cannot determine active task on cpu %ld\n", cpu); > diff --git a/task.c b/task.c > index ebdb5be3786f..3a190cafbacb 100644 > --- a/task.c > +++ b/task.c > @@ -5301,7 +5301,9 @@ set_context(ulong task, ulong pid) > > if (found) { > CURRENT_CONTEXT() = tc; > - return TRUE; > + > + /* change the selected thread in gdb, according to current context */ > + return gdb_change_cpu_context(tc->processor); > } else { > if (task) > error(INFO, "cannot set context for task: %lx\n", task);

Currently for most gdb_interface call with a non-null file pointer, GDB's output stream is replaced with the passed file pointer 'info threads', which is a gdb passthrough, fails to print all thread after support was added to get registers from crash_target: Id Target Id Frame 1 CPU 0 <unavailable> in ?? () 2 CPU 1 Also, it was noticed that 'info threads' will print all threads when 'info threads' is run 2nd and subsequent times. This incomplete output of 'info threads' was due to a subtle bug in gdb_interface. For any passthrough, it switches the gdb output and stderr streams to another FILE* passed in `struct gnu_request`. But it does not restore the original FILE* stream gdb was using. For each thread, which does not have it's registers yet, gdb goes to crash_target::fetch_registers to ask for registers. Which in turn might call 'datatype_info', which causes gdb's output stream to be set to '/dev/null' So all output after the call to datatype_info will go to /dev/null, and hence the data to be printed is lost. When 'info threads' is run a second time, it sets GDB's output streams to something which is NOT /dev/null, and since it already has registers for each thread, it does not go to 'crash_target::fetch_registers' and hence the output stream is consistent, and we get complete output So what happened is this: 1. GDB prints thread 1 (CPU 0) correctly since it had it's registers cached during initialisation in 'crash_target_init' (at that times registers where still unavailable, so it shows unavailable) 2. At CPU 1, to print the frame, it goes to 'crash_target::fetch_registers' to get the registers 3. crash_target then calls 'machdep->get_cpu_reg' which finally ends up at 'get_netdump_regs' which uses 'datatype_info' to get info of 'elf_prstatus.pr_reg' 4. Inside 'datatype_info', we set the file stream to /dev/null (pc->nullfp). Then it passes this request object to gdb_interface 5. gdb_interface replaces GDB's output stream to the passed stream, ie. /dev/null 6. Now, ALL FUTURE WRITES EVEN BY GDB, SUCH AS FOR THE 'info threads' COMMAND GOES TO THIS STREAM gnu_request->fp, WHICH is /dev/null, until someone else sets the non-null stream later 7. Similar behaviour occurs with all other threads 8. And hence we lose all subsequent output by GDB also When 'info threads' is run a second time: 1. 'gdb_pass_through' passes a default FILE* to 'gdb_interface', which is not /dev/null 2. Since the registers are cached for all threads now, it does not go back to 'crash_target' for registers, and hence no call is made to 'datatype_info', hence GDB's output stream is not changing 3. Since the gdb's stream, even though not what it was using originally, it's still valid, and not '/dev/null', hence we get the complete output Fix this by restoring the original output streams, after gdb_interface has handled the output Signed-off-by: Aditya Gupta <adityag(a)linux.ibm.com&gt; --- gdb-10.2.patch | 46 +++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 45 insertions(+), 1 deletion(-) diff --git a/gdb-10.2.patch b/gdb-10.2.patch index 8c1b43eb07b7..a4e45fa0e6fa 100644 --- a/gdb-10.2.patch +++ b/gdb-10.2.patch @@ -1484,13 +1484,29 @@ exit 0 + } +} +#endif +--- gdb-10.2/gdb/ui-file.c.orig ++++ gdb-10.2/gdb/ui-file.c +@@ -161,6 +161,12 @@ stdio_file::~stdio_file () + fclose (m_file); + } + ++FILE* ++stdio_file::get_stream(void) ++{ ++ return m_file; ++} ++ + void + stdio_file::set_stream (FILE *file) + { --- gdb-10.2/gdb/ui-file.h.orig +++ gdb-10.2/gdb/ui-file.h -@@ -195,10 +195,10 @@ class stdio_file : public ui_file +@@ -195,10 +195,11 @@ class stdio_file : public ui_file bool can_emit_style_escape () override; -private: ++ FILE *get_stream(void); /* Sets the internal stream to FILE, and saves the FILE's file descriptor in M_FD. */ void set_stream (FILE *file); @@ -3267,3 +3283,31 @@ exit 0 for (compunit_symtab *cust : objfile->compunits ()) { +--- gdb-10.2/gdb/symtab.c.orig ++++ gdb-10.2/gdb/symtab.c +@@ -6964,8 +6964,12 @@ void + gdb_command_funnel_1(struct gnu_request *req) + { + struct symbol *sym; ++ FILE *original_stdout_stream = nullptr; ++ FILE *original_stderr_stream = nullptr; + + if (req->command != GNU_VERSION && req->command != GNU_USER_PRINT_OPTION) { ++ original_stdout_stream = (dynamic_cast< stdio_file * >gdb_stdout)->get_stream(); ++ original_stderr_stream = (dynamic_cast< stdio_file * >gdb_stderr)->get_stream(); + (dynamic_cast<stdio_file *>gdb_stdout)->set_stream(req->fp); + (dynamic_cast<stdio_file *>gdb_stderr)->set_stream(req->fp); + } +@@ -7068,6 +7072,12 @@ gdb_command_funnel_1(struct gnu_request *req) + req->flags |= GNU_COMMAND_FAILED; + break; + } ++ ++ /* Restore the streams gdb output was using */ ++ if (original_stdout_stream) ++ (dynamic_cast<stdio_file *>gdb_stdout)->set_stream(original_stdout_stream); ++ if (original_stderr_stream) ++ (dynamic_cast<stdio_file *>gdb_stderr)->set_stream(original_stderr_stream); + } + + /* -- 2.43.0

Currently the output is like this ppc64le: crash> info threads Id Target Id Frame 1 CPU 0 <unavailable> in ?? () 2 CPU 1 0xc000000000025d00 in ppc_panic_event (this=<optimized out>, event=<optimized out>, ptr=0x0) at arch/powerpc/kernel/setup-common.c:712 3 CPU 2 0xc000000000025d00 in ppc_panic_event (this=<optimized out>, event=<optimized out>, ptr=0x0) at arch/powerpc/kernel/setup-common.c:712 4 CPU 3 0xc000000000025d00 in ppc_panic_event (this=<optimized out>, event=<optimized out>, ptr=0x0) at arch/powerpc/kernel/setup-common.c:712 * 5 CPU 4 0xc000000000025d00 in ppc_panic_event (this=<optimized out>, event=<optimized out>, ptr=0x0) at arch/powerpc/kernel/setup-common.c:712 6 CPU 5 0xc000000000025d00 in ppc_panic_event (this=<optimized out>, event=<optimized out>, ptr=0x0) at arch/powerpc/kernel/setup-common.c:712 7 CPU 6 0xc000000000025d00 in ppc_panic_event (this=<optimized out>, event=<optimized out>, ptr=0x0) at arch/powerpc/kernel/setup-common.c:712 8 CPU 7 0xc000000000025d00 in ppc_panic_event (this=<optimized out>, event=<optimized out>, ptr=0x0) at arch/powerpc/kernel/setup-common.c:712 There are two issues here: 1. CPU 0 always shows '<unavailable>' frame: This is due to 'thread 0' being initialised in 'crash_target_init', but it's very early in crash init, so it could not get any registers from the vmcore. And, since GDB caches registers (whether it is there or now), it keeps thinking that registers for this thread are unavailable, so all future usage of thread 0 also shows unavailable registers & frame Fix this by refreshing the register cache of all threads in 'gdb_refresh_regcache', at task_init 2. All other CPUs show the same frame: For each thread, GDB depends on crash to give it registers, ie. crash_target::fetch_registers, but this in turn depends on crash's current context GDB internally switches it's thread context internally to each thread one by one, while printing the thread's frame, similarly switch crash's context when the thread context is changed, so that it matches the thread context in gdb (such as, CPU 3 in crash for thread 2(CPU 3) in gdb). Also, since we are switching context multiple times, add an argument to 'set_cpu' to not print the context everytime With these fixed, it will show all threads, as well as correct registers and frame. It might still show similar frame for many threads, due to all of them being on same NMI exception crash path, but if checked with 'info registers', they will have different registers. Signed-off-by: Aditya Gupta <adityag(a)linux.ibm.com&gt; --- crash_target.c | 37 +++++++++++++++++++++++++++++++++++-- defs.h | 5 +++-- gdb-10.2.patch | 40 +++++++++++++++++++++++++++++++++++++--- kernel.c | 8 +++++--- task.c | 30 ++++++++++++++++++++++-------- tools.c | 10 +++++----- 6 files changed, 107 insertions(+), 23 deletions(-) diff --git a/crash_target.c b/crash_target.c index a9d7eea8a80e..d06383f594aa 100644 --- a/crash_target.c +++ b/crash_target.c @@ -30,7 +30,8 @@ extern "C" int crash_get_nr_cpus(void); extern "C" int crash_get_cpu_reg (int cpu, int regno, const char *regname, int regsize, void *val); extern "C" int gdb_change_cpu_context (unsigned int cpu); -extern "C" int set_cpu (int cpu); +extern "C" void gdb_refresh_regcache(unsigned int cpu); +extern "C" int set_cpu(int cpu, int print_context); /* The crash target. */ @@ -150,10 +151,42 @@ gdb_change_cpu_context(unsigned int cpu) return FALSE; /* Making sure that crash's context is same */ - set_cpu(cpu); + set_cpu(cpu, FALSE); /* Switch to the thread */ switch_to_thread(tp); + + /* Fetch/Refresh thread's registers */ + gdb_refresh_regcache(cpu); + return TRUE; } +/* Refresh regcache of gdb thread on given CPU + * + * When gdb threads were initially added by 'crash_target_init', crash was not + * yet initialised, and hence crash_target::fetch_registers didn't give any + * registers to gdb. + * + * This is meant to be called after tasks in crash have been initialised, and + * possible machdep->get_cpu_reg is also set so architecture can give registers + */ +extern "C" void +gdb_refresh_regcache(unsigned int cpu) +{ + int saved_cpu = inferior_thread()->ptid.tid(); + ptid_t ptid = ptid_t(CRASH_INFERIOR_PID, 0, cpu); + inferior *inf = current_inferior(); + thread_info *tp = find_thread_ptid (inf, ptid); + + if (tp == NULL) { + warning("gdb thread for cpu %d not found\n", cpu); + return; + } + + /* temporarily switch to the cpu so we get correct registers */ + set_cpu(cpu, FALSE); + target_fetch_registers(get_thread_regcache(tp), -1); + + set_cpu(saved_cpu, FALSE); +} diff --git a/defs.h b/defs.h index 7f7a12753658..ba4a6a606f66 100644 --- a/defs.h +++ b/defs.h @@ -5940,7 +5940,7 @@ extern char *help_map[]; * task.c */ void task_init(void); -int set_context(ulong, ulong); +int set_context(ulong, ulong, uint); void show_context(struct task_context *); ulong pid_to_task(ulong); ulong task_to_pid(ulong); @@ -6044,7 +6044,7 @@ void parse_kernel_version(char *); #define SHOW_LOG_AUDIT (0x8) #define SHOW_LOG_CTIME (0x10) #define SHOW_LOG_SAFE (0x20) -void set_cpu(int); +void set_cpu(int cpu, int print_context); void clear_machdep_cache(void); struct stack_hook *gather_text_list(struct bt_info *); int get_cpus_online(void); @@ -7978,5 +7978,6 @@ enum ppc64_regnum { /* crash_target.c */ extern int gdb_change_cpu_context (unsigned int cpu); +extern void gdb_refresh_regcache (unsigned int cpu); #endif /* !GDB_COMMON */ diff --git a/gdb-10.2.patch b/gdb-10.2.patch index a4e45fa0e6fa..9051c83ac784 100644 --- a/gdb-10.2.patch +++ b/gdb-10.2.patch @@ -494,13 +494,47 @@ exit 0 +#ifdef CRASH_MERGE +/* Function to set cpu, defined by crash-utility */ -+extern "C" void set_cpu (int); ++extern "C" void set_cpu(int cpu, int print_context); +#endif + /* RAII type used to increase / decrease the refcount of each thread in a given list of threads. */ -@@ -1896,7 +1901,13 @@ thread_command (const char *tidstr, int from_tty) +@@ -1093,6 +1098,9 @@ print_thread_info_1 (struct ui_out *uiout, const char *requested_threads, + uiout->table_body (); + } + ++#ifdef CRASH_MERGE ++ int current_cpu = current_thread ? current_thread->ptid.tid() : 0; ++#endif + for (inferior *inf : all_inferiors ()) + for (thread_info *tp : inf->threads ()) + { +@@ -1108,6 +1116,11 @@ print_thread_info_1 (struct ui_out *uiout, const char *requested_threads, + + ui_out_emit_tuple tuple_emitter (uiout, NULL); + ++ /* Switch to the thread's CPU in crash */ ++#ifdef CRASH_MERGE ++ set_cpu(tp->ptid.tid(), FALSE); ++#endif ++ + if (!uiout->is_mi_like_p ()) + { + if (tp == current_thread) +@@ -1180,6 +1193,11 @@ print_thread_info_1 (struct ui_out *uiout, const char *requested_threads, + /* This end scope restores the current thread and the frame + selected before the "info threads" command, and it finishes the + ui-out list or table. */ ++ ++#ifdef CRASH_MERGE ++ /* Restore crash's context */ ++ set_cpu(current_cpu, FALSE); ++#endif + } + + if (pid == -1 && requested_threads == NULL) +@@ -1896,7 +1914,13 @@ thread_command (const char *tidstr, int from_tty) { ptid_t previous_ptid = inferior_ptid; @@ -508,7 +542,7 @@ exit 0 + struct thread_info* thread_id = parse_thread_id (tidstr, NULL); + +#ifdef CRASH_MERGE -+ set_cpu(thread_id->ptid.tid()); ++ set_cpu(thread_id->ptid.tid(), FALSE); +#endif + + thread_select (tidstr, thread_id); diff --git a/kernel.c b/kernel.c index a8d60507dd95..505cffde1cf8 100644 --- a/kernel.c +++ b/kernel.c @@ -6491,9 +6491,10 @@ no_cpu_flags: /* * Set the context to the active task on a given cpu -- dumpfiles only. + * Optionally show the context if print_context is TRUE */ void -set_cpu(int cpu) +set_cpu(int cpu, int print_context) { ulong task; @@ -6511,11 +6512,12 @@ set_cpu(int cpu) return; if (task) - set_context(task, NO_PID); + set_context(task, NO_PID, TRUE); else error(FATAL, "cannot determine active task on cpu %ld\n", cpu); - show_context(CURRENT_CONTEXT()); + if (print_context) + show_context(CURRENT_CONTEXT()); } diff --git a/task.c b/task.c index 3a190cafbacb..a405b05a47d1 100644 --- a/task.c +++ b/task.c @@ -672,7 +672,7 @@ task_init(void) if (ACTIVE()) { active_pid = REMOTE() ? pc->server_pid : LOCAL_ACTIVE() ? pc->program_pid : 1; - set_context(NO_TASK, active_pid); + set_context(NO_TASK, active_pid, FALSE); tt->this_task = pid_to_task(active_pid); } else { @@ -684,7 +684,7 @@ task_init(void) else if (ELF_NOTES_VALID() && DISKDUMP_DUMPFILE()) map_cpus_to_prstatus_kdump_cmprs(); please_wait("determining panic task"); - set_context(get_panic_context(), NO_PID); + set_context(get_panic_context(), NO_PID, TRUE); please_wait_done(); } @@ -706,6 +706,17 @@ task_init(void) kt->boot_date.tv_nsec = 0; } + /* + * Refresh CPU 0's thread's regcache + * + * This is required since, it's registers were initialised in + * crash_target_init when crash was not initialised yet and hence could + * not pass registers to gdb when gdb requests via + * crash_target::fetch_registers, so CPU 0's registers are shown as + * <unavailable> in gdb mode + * */ + gdb_refresh_regcache(0); + tt->flags |= TASK_INIT_DONE; } @@ -2985,9 +2996,9 @@ refresh_context(ulong curtask, ulong curpid) struct task_context *tc; if (task_exists(curtask) && pid_exists(curpid)) { - set_context(curtask, NO_PID); + set_context(curtask, NO_PID, FALSE); } else { - set_context(tt->this_task, NO_PID); + set_context(tt->this_task, NO_PID, FALSE); complain = TRUE; if (STREQ(args[0], "set") && (argcnt == 2) && @@ -3053,7 +3064,7 @@ sort_context_array(void) curtask = CURRENT_TASK(); qsort((void *)tt->context_array, (size_t)tt->running_tasks, sizeof(struct task_context), sort_by_pid); - set_context(curtask, NO_PID); + set_context(curtask, NO_PID, FALSE); sort_context_by_task(); } @@ -3100,7 +3111,7 @@ sort_context_array_by_last_run(void) curtask = CURRENT_TASK(); qsort((void *)tt->context_array, (size_t)tt->running_tasks, sizeof(struct task_context), sort_by_last_run); - set_context(curtask, NO_PID); + set_context(curtask, NO_PID, FALSE); sort_context_by_task(); } @@ -5281,7 +5292,7 @@ comm_exists(char *s) * that pid is selected. */ int -set_context(ulong task, ulong pid) +set_context(ulong task, ulong pid, uint update_gdb_thread) { int i; struct task_context *tc; @@ -5303,7 +5314,10 @@ set_context(ulong task, ulong pid) CURRENT_CONTEXT() = tc; /* change the selected thread in gdb, according to current context */ - return gdb_change_cpu_context(tc->processor); + if (update_gdb_thread) + return gdb_change_cpu_context(tc->processor); + else + return TRUE; } else { if (task) error(INFO, "cannot set context for task: %lx\n", task); diff --git a/tools.c b/tools.c index 0f2db108838a..9b149fb27fcb 100644 --- a/tools.c +++ b/tools.c @@ -1860,7 +1860,7 @@ cmd_set(void) break; } cpu = dtoi(optarg, FAULT_ON_ERROR, NULL); - set_cpu(cpu); + set_cpu(cpu, TRUE); return; case 'p': @@ -1871,7 +1871,7 @@ cmd_set(void) return; if (ACTIVE()) { - set_context(tt->this_task, NO_PID); + set_context(tt->this_task, NO_PID, FALSE); show_context(CURRENT_CONTEXT()); return; } @@ -1880,7 +1880,7 @@ cmd_set(void) error(INFO, "no panic task found!\n"); return; } - set_context(tt->panic_task, NO_PID); + set_context(tt->panic_task, NO_PID, FALSE); show_context(CURRENT_CONTEXT()); return; @@ -2559,14 +2559,14 @@ cmd_set(void) case STR_PID: pid = value; task = NO_TASK; - if (set_context(task, pid)) + if (set_context(task, pid, FALSE)) show_context(CURRENT_CONTEXT()); break; case STR_TASK: task = value; pid = NO_PID; - if (set_context(task, pid)) + if (set_context(task, pid, FALSE)) show_context(CURRENT_CONTEXT()); break; -- 2.43.0