Date: Sun, 25 Sep 2016 16:30:30 +0000 (UTC) From: Bruce Evans <bde@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r306311 - in head: share/man/man4 sys/ddb sys/i386/i386 sys/i386/include Message-ID: <201609251630.u8PGUUwU001468@repo.freebsd.org>
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Author: bde Date: Sun Sep 25 16:30:29 2016 New Revision: 306311 URL: https://svnweb.freebsd.org/changeset/base/306311 Log: Determine the operand/address size of %cs in a new function db_segsize(). Use db_segsize() to set the default operand/address size for disassembling. Allow overriding this with the "alternate" display format /I. The API of db_disasm() should be debooleanized to pass a more general request (amd64 needs overrides to sizes of 16, 32, and 64, but this commit doesn't implement anything for amd64 since much larger changes are needed to restore the amd64 disassmbler's support for non-default sizes). Fix db_print_loc_and_inst() to ask for the normal format and not the alternate in normal operation. This is most useful for vm86 mode, but also works for 16-bit protected mode. Use db_segsize() to avoid trying to print a garbage stack trace if %cs is 16 bits. Print something like the stack trace termination message for a trap boundary instead. Document that the alternate format is now useful on i386. Modified: head/share/man/man4/ddb.4 head/sys/ddb/db_examine.c head/sys/i386/i386/db_disasm.c head/sys/i386/i386/db_interface.c head/sys/i386/i386/db_trace.c head/sys/i386/include/db_machdep.h Modified: head/share/man/man4/ddb.4 ============================================================================== --- head/share/man/man4/ddb.4 Sun Sep 25 14:56:24 2016 (r306310) +++ head/share/man/man4/ddb.4 Sun Sep 25 16:30:29 2016 (r306311) @@ -264,7 +264,9 @@ The location is also displayed in hex at display as an instruction .It Cm I display as an instruction with possible alternate formats depending on the -machine, but none of the supported architectures have an alternate format +machine. +On i386, this selects the alternate format for the instruction decoding +(16 bits in a 32-bit code segment and vice versa). .It Cm S display a symbol name for the pointer stored at the address .El Modified: head/sys/ddb/db_examine.c ============================================================================== --- head/sys/ddb/db_examine.c Sun Sep 25 14:56:24 2016 (r306310) +++ head/sys/ddb/db_examine.c Sun Sep 25 16:30:29 2016 (r306311) @@ -241,7 +241,7 @@ db_print_loc_and_inst(db_addr_t loc) db_printsym(loc, DB_STGY_PROC); if (db_search_symbol(loc, DB_STGY_PROC, &off) != C_DB_SYM_NULL) { db_printf(":\t"); - (void)db_disasm(loc, true); + (void)db_disasm(loc, false); } } Modified: head/sys/i386/i386/db_disasm.c ============================================================================== --- head/sys/i386/i386/db_disasm.c Sun Sep 25 14:56:24 2016 (r306310) +++ head/sys/i386/i386/db_disasm.c Sun Sep 25 16:30:29 2016 (r306311) @@ -31,6 +31,7 @@ __FBSDID("$FreeBSD$"); * Instruction disassembler. */ #include <sys/param.h> +#include <sys/kdb.h> #include <ddb/ddb.h> #include <ddb/db_access.h> @@ -1168,9 +1169,17 @@ db_disasm(db_addr_t loc, bool altfmt) int len; struct i_addr address; + if (db_segsize(kdb_frame) == 16) + altfmt = !altfmt; get_value_inc(inst, loc, 1, FALSE); - short_addr = FALSE; - size = LONG; + if (altfmt) { + short_addr = TRUE; + size = WORD; + } + else { + short_addr = FALSE; + size = LONG; + } seg = NULL; /* Modified: head/sys/i386/i386/db_interface.c ============================================================================== --- head/sys/i386/i386/db_interface.c Sun Sep 25 14:56:24 2016 (r306310) +++ head/sys/i386/i386/db_interface.c Sun Sep 25 16:30:29 2016 (r306311) @@ -135,6 +135,30 @@ db_write_bytes(vm_offset_t addr, size_t return (ret); } +int +db_segsize(struct trapframe *tfp) +{ + struct proc_ldt *plp; + struct segment_descriptor *sdp; + int sel; + + if (tfp == NULL) + return (32); + if (tfp->tf_eflags & PSL_VM) + return (16); + sel = tfp->tf_cs & 0xffff; + if (sel == GSEL(GCODE_SEL, SEL_KPL)) + return (32); + /* Rare cases follow. User mode cases are currently unreachable. */ + if (ISLDT(sel)) { + plp = curthread->td_proc->p_md.md_ldt; + sdp = (plp != NULL) ? &plp->ldt_sd : &ldt[0].sd; + } else { + sdp = &gdt[PCPU_GET(cpuid) * NGDT].sd; + } + return (sdp[IDXSEL(sel)].sd_def32 == 0 ? 16 : 32); +} + void db_show_mdpcpu(struct pcpu *pc) { Modified: head/sys/i386/i386/db_trace.c ============================================================================== --- head/sys/i386/i386/db_trace.c Sun Sep 25 14:56:24 2016 (r306310) +++ head/sys/i386/i386/db_trace.c Sun Sep 25 16:30:29 2016 (r306311) @@ -421,6 +421,17 @@ db_backtrace(struct thread *td, struct t int instr, narg; boolean_t first; + if (db_segsize(tf) == 16) { + db_printf( +"--- 16-bit%s, cs:eip = %#x:%#x, ss:esp = %#x:%#x, ebp = %#x, tf = %p ---\n", + (tf->tf_eflags & PSL_VM) ? " (vm86)" : "", + tf->tf_cs, tf->tf_eip, + TF_HAS_STACKREGS(tf) ? tf->tf_ss : rss(), + TF_HAS_STACKREGS(tf) ? tf->tf_esp : (intptr_t)&tf->tf_esp, + tf->tf_ebp, tf); + return (0); + } + /* * If an indirect call via an invalid pointer caused a trap, * %pc contains the invalid address while the return address Modified: head/sys/i386/include/db_machdep.h ============================================================================== --- head/sys/i386/include/db_machdep.h Sun Sep 25 14:56:24 2016 (r306310) +++ head/sys/i386/include/db_machdep.h Sun Sep 25 16:30:29 2016 (r306311) @@ -98,4 +98,6 @@ do { \ #define DB_SMALL_VALUE_MAX 0x7fffffff #define DB_SMALL_VALUE_MIN (-0x400001) +int db_segsize(struct trapframe *tfp); + #endif /* !_MACHINE_DB_MACHDEP_H_ */
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