/* Target-dependent code for GDB, the GNU debugger.
- Copyright 1986, 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 2000
- Free Software Foundation, Inc.
+
+ Copyright 1986, 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996,
+ 1997, 2000, 2001, 2002 Free Software Foundation, Inc.
This file is part of GDB.
#include "gdbcmd.h"
#include "symfile.h"
#include "objfiles.h"
+#include "regcache.h"
+#include "value.h"
+
+#include "solib-svr4.h"
+#include "ppc-tdep.h"
/* The following two instructions are used in the signal trampoline
- code on linux/ppc */
+ code on GNU/Linux PPC. */
#define INSTR_LI_R0_0x7777 0x38007777
#define INSTR_SC 0x44000002
#define PPC_LINUX_PT_FPR31 (PPC_LINUX_PT_FPR0 + 2*31)
#define PPC_LINUX_PT_FPSCR (PPC_LINUX_PT_FPR0 + 2*32 + 1)
+static int ppc_linux_at_sigtramp_return_path (CORE_ADDR pc);
+
/* Determine if pc is in a signal trampoline...
- Ha! That's not what this does at all. wait_for_inferior in infrun.c
- calls IN_SIGTRAMP in order to detect entry into a signal trampoline
- just after delivery of a signal. But on linux, signal trampolines
- are used for the return path only. The kernel sets things up so that
- the signal handler is called directly.
+ Ha! That's not what this does at all. wait_for_inferior in
+ infrun.c calls PC_IN_SIGTRAMP in order to detect entry into a
+ signal trampoline just after delivery of a signal. But on
+ GNU/Linux, signal trampolines are used for the return path only.
+ The kernel sets things up so that the signal handler is called
+ directly.
If we use in_sigtramp2() in place of in_sigtramp() (see below)
we'll (often) end up with stop_pc in the trampoline and prev_pc in
first instruction long after the fact, just in case the observed
behavior is ever fixed.)
- IN_SIGTRAMP is called from blockframe.c as well in order to set
+ PC_IN_SIGTRAMP is called from blockframe.c as well in order to set
the signal_handler_caller flag. Because of our strange definition
- of in_sigtramp below, we can't rely on signal_handler_caller getting
- set correctly from within blockframe.c. This is why we take pains
- to set it in init_extra_frame_info(). */
+ of in_sigtramp below, we can't rely on signal_handler_caller
+ getting set correctly from within blockframe.c. This is why we
+ take pains to set it in init_extra_frame_info(). */
int
ppc_linux_in_sigtramp (CORE_ADDR pc, char *func_name)
char buf[4];
CORE_ADDR handler;
- lr = read_register (LR_REGNUM);
+ lr = read_register (gdbarch_tdep (current_gdbarch)->ppc_lr_regnum);
if (!ppc_linux_at_sigtramp_return_path (lr))
return 0;
* instructions. It'd be faster though if we could find a way to do this
* via some simple address comparisons.
*/
-int
+static int
ppc_linux_at_sigtramp_return_path (CORE_ADDR pc)
{
char buf[12];
/* The rs6000 version of FRAME_SAVED_PC will almost work for us. The
signal handler details are different, so we'll handle those here
and call the rs6000 version to do the rest. */
-unsigned long
+CORE_ADDR
ppc_linux_frame_saved_pc (struct frame_info *fi)
{
if (fi->signal_handler_caller)
{
CORE_ADDR regs_addr =
- read_memory_integer (fi->frame + PPC_LINUX_REGS_PTR_OFFSET, 4);
+ read_memory_integer (fi->frame + PPC_LINUX_REGS_PTR_OFFSET, 4);
/* return the NIP in the regs array */
return read_memory_integer (regs_addr + 4 * PPC_LINUX_PT_NIP, 4);
}
-
- return rs6000_frame_saved_pc (fi);
+ else if (fi->next && fi->next->signal_handler_caller)
+ {
+ CORE_ADDR regs_addr =
+ read_memory_integer (fi->next->frame + PPC_LINUX_REGS_PTR_OFFSET, 4);
+ /* return LNK in the regs array */
+ return read_memory_integer (regs_addr + 4 * PPC_LINUX_PT_LNK, 4);
+ }
+ else
+ return rs6000_frame_saved_pc (fi);
}
void
regs_addr =
read_memory_integer (fi->frame + PPC_LINUX_REGS_PTR_OFFSET, 4);
fi->saved_regs[PC_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_NIP;
- fi->saved_regs[PS_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_MSR;
- fi->saved_regs[CR_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_CCR;
- fi->saved_regs[LR_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_LNK;
- fi->saved_regs[CTR_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_CTR;
- fi->saved_regs[XER_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_XER;
- fi->saved_regs[MQ_REGNUM] = regs_addr + 4 * PPC_LINUX_PT_MQ;
+ fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_ps_regnum] =
+ regs_addr + 4 * PPC_LINUX_PT_MSR;
+ fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_cr_regnum] =
+ regs_addr + 4 * PPC_LINUX_PT_CCR;
+ fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_lr_regnum] =
+ regs_addr + 4 * PPC_LINUX_PT_LNK;
+ fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_ctr_regnum] =
+ regs_addr + 4 * PPC_LINUX_PT_CTR;
+ fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_xer_regnum] =
+ regs_addr + 4 * PPC_LINUX_PT_XER;
+ fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_mq_regnum] =
+ regs_addr + 4 * PPC_LINUX_PT_MQ;
for (i = 0; i < 32; i++)
- fi->saved_regs[GP0_REGNUM + i] = regs_addr + 4 * PPC_LINUX_PT_R0 + 4 * i;
+ fi->saved_regs[gdbarch_tdep (current_gdbarch)->ppc_gp0_regnum + i] =
+ regs_addr + 4 * PPC_LINUX_PT_R0 + 4 * i;
for (i = 0; i < 32; i++)
fi->saved_regs[FP0_REGNUM + i] = regs_addr + 4 * PPC_LINUX_PT_FPR0 + 8 * i;
}
return rs6000_frame_chain (thisframe);
}
-/* FIXME: Move the following to rs6000-tdep.c (or some other file where
- it may be used generically by ports which use either the SysV ABI or
- the EABI */
+/* ppc_linux_memory_remove_breakpoints attempts to remove a breakpoint
+ in much the same fashion as memory_remove_breakpoint in mem-break.c,
+ but is careful not to write back the previous contents if the code
+ in question has changed in between inserting the breakpoint and
+ removing it.
+
+ Here is the problem that we're trying to solve...
+
+ Once upon a time, before introducing this function to remove
+ breakpoints from the inferior, setting a breakpoint on a shared
+ library function prior to running the program would not work
+ properly. In order to understand the problem, it is first
+ necessary to understand a little bit about dynamic linking on
+ this platform.
+
+ A call to a shared library function is accomplished via a bl
+ (branch-and-link) instruction whose branch target is an entry
+ in the procedure linkage table (PLT). The PLT in the object
+ file is uninitialized. To gdb, prior to running the program, the
+ entries in the PLT are all zeros.
+
+ Once the program starts running, the shared libraries are loaded
+ and the procedure linkage table is initialized, but the entries in
+ the table are not (necessarily) resolved. Once a function is
+ actually called, the code in the PLT is hit and the function is
+ resolved. In order to better illustrate this, an example is in
+ order; the following example is from the gdb testsuite.
+
+ We start the program shmain.
+
+ [kev@arroyo testsuite]$ ../gdb gdb.base/shmain
+ [...]
+
+ We place two breakpoints, one on shr1 and the other on main.
+
+ (gdb) b shr1
+ Breakpoint 1 at 0x100409d4
+ (gdb) b main
+ Breakpoint 2 at 0x100006a0: file gdb.base/shmain.c, line 44.
+
+ Examine the instruction (and the immediatly following instruction)
+ upon which the breakpoint was placed. Note that the PLT entry
+ for shr1 contains zeros.
+
+ (gdb) x/2i 0x100409d4
+ 0x100409d4 <shr1>: .long 0x0
+ 0x100409d8 <shr1+4>: .long 0x0
+
+ Now run 'til main.
+
+ (gdb) r
+ Starting program: gdb.base/shmain
+ Breakpoint 1 at 0xffaf790: file gdb.base/shr1.c, line 19.
+
+ Breakpoint 2, main ()
+ at gdb.base/shmain.c:44
+ 44 g = 1;
+
+ Examine the PLT again. Note that the loading of the shared
+ library has initialized the PLT to code which loads a constant
+ (which I think is an index into the GOT) into r11 and then
+ branchs a short distance to the code which actually does the
+ resolving.
+
+ (gdb) x/2i 0x100409d4
+ 0x100409d4 <shr1>: li r11,4
+ 0x100409d8 <shr1+4>: b 0x10040984 <sg+4>
+ (gdb) c
+ Continuing.
+
+ Breakpoint 1, shr1 (x=1)
+ at gdb.base/shr1.c:19
+ 19 l = 1;
+
+ Now we've hit the breakpoint at shr1. (The breakpoint was
+ reset from the PLT entry to the actual shr1 function after the
+ shared library was loaded.) Note that the PLT entry has been
+ resolved to contain a branch that takes us directly to shr1.
+ (The real one, not the PLT entry.)
+
+ (gdb) x/2i 0x100409d4
+ 0x100409d4 <shr1>: b 0xffaf76c <shr1>
+ 0x100409d8 <shr1+4>: b 0x10040984 <sg+4>
+
+ The thing to note here is that the PLT entry for shr1 has been
+ changed twice.
+
+ Now the problem should be obvious. GDB places a breakpoint (a
+ trap instruction) on the zero value of the PLT entry for shr1.
+ Later on, after the shared library had been loaded and the PLT
+ initialized, GDB gets a signal indicating this fact and attempts
+ (as it always does when it stops) to remove all the breakpoints.
+
+ The breakpoint removal was causing the former contents (a zero
+ word) to be written back to the now initialized PLT entry thus
+ destroying a portion of the initialization that had occurred only a
+ short time ago. When execution continued, the zero word would be
+ executed as an instruction an an illegal instruction trap was
+ generated instead. (0 is not a legal instruction.)
+
+ The fix for this problem was fairly straightforward. The function
+ memory_remove_breakpoint from mem-break.c was copied to this file,
+ modified slightly, and renamed to ppc_linux_memory_remove_breakpoint.
+ In tm-linux.h, MEMORY_REMOVE_BREAKPOINT is defined to call this new
+ function.
+
+ The differences between ppc_linux_memory_remove_breakpoint () and
+ memory_remove_breakpoint () are minor. All that the former does
+ that the latter does not is check to make sure that the breakpoint
+ location actually contains a breakpoint (trap instruction) prior
+ to attempting to write back the old contents. If it does contain
+ a trap instruction, we allow the old contents to be written back.
+ Otherwise, we silently do nothing.
+
+ The big question is whether memory_remove_breakpoint () should be
+ changed to have the same functionality. The downside is that more
+ traffic is generated for remote targets since we'll have an extra
+ fetch of a memory word each time a breakpoint is removed.
+
+ For the time being, we'll leave this self-modifying-code-friendly
+ version in ppc-linux-tdep.c, but it ought to be migrated somewhere
+ else in the event that some other platform has similar needs with
+ regard to removing breakpoints in some potentially self modifying
+ code. */
+int
+ppc_linux_memory_remove_breakpoint (CORE_ADDR addr, char *contents_cache)
+{
+ const unsigned char *bp;
+ int val;
+ int bplen;
+ char old_contents[BREAKPOINT_MAX];
-/* round2 rounds x up to the nearest multiple of s assuming that s is a
- power of 2 */
+ /* Determine appropriate breakpoint contents and size for this address. */
+ bp = BREAKPOINT_FROM_PC (&addr, &bplen);
+ if (bp == NULL)
+ error ("Software breakpoints not implemented for this target.");
-#undef round2
-#define round2(x,s) ((((long) (x) - 1) & ~(long)((s)-1)) + (s))
+ val = target_read_memory (addr, old_contents, bplen);
-/* Pass the arguments in either registers, or in the stack. Using the
- ppc sysv ABI, the first eight words of the argument list (that might
- be less than eight parameters if some parameters occupy more than one
- word) are passed in r3..r10 registers. float and double parameters are
- passed in fpr's, in addition to that. Rest of the parameters if any
- are passed in user stack.
+ /* If our breakpoint is no longer at the address, this means that the
+ program modified the code on us, so it is wrong to put back the
+ old value */
+ if (val == 0 && memcmp (bp, old_contents, bplen) == 0)
+ val = target_write_memory (addr, contents_cache, bplen);
- If the function is returning a structure, then the return address is passed
- in r3, then the first 7 words of the parametes can be passed in registers,
- starting from r4. */
+ return val;
+}
-CORE_ADDR
-ppc_sysv_abi_push_arguments (nargs, args, sp, struct_return, struct_addr)
- int nargs;
- value_ptr *args;
- CORE_ADDR sp;
- int struct_return;
- CORE_ADDR struct_addr;
+/* Fetch (and possibly build) an appropriate link_map_offsets
+ structure for GNU/Linux PPC targets using the struct offsets
+ defined in link.h (but without actual reference to that file).
+
+ This makes it possible to access GNU/Linux PPC shared libraries
+ from a GDB that was not built on an GNU/Linux PPC host (for cross
+ debugging). */
+
+struct link_map_offsets *
+ppc_linux_svr4_fetch_link_map_offsets (void)
{
- int argno;
- int greg, freg;
- int argstkspace;
- int structstkspace;
- int argoffset;
- int structoffset;
- value_ptr arg;
- struct type *type;
- int len;
- char old_sp_buf[4];
- CORE_ADDR saved_sp;
-
- greg = struct_return ? 4 : 3;
- freg = 1;
- argstkspace = 0;
- structstkspace = 0;
-
- /* Figure out how much new stack space is required for arguments
- which don't fit in registers. Unlike the PowerOpen ABI, the
- SysV ABI doesn't reserve any extra space for parameters which
- are put in registers. */
- for (argno = 0; argno < nargs; argno++)
+ static struct link_map_offsets lmo;
+ static struct link_map_offsets *lmp = NULL;
+
+ if (lmp == NULL)
{
- arg = args[argno];
- type = check_typedef (VALUE_TYPE (arg));
- len = TYPE_LENGTH (type);
-
- if (TYPE_CODE (type) == TYPE_CODE_FLT)
- {
- if (freg <= 8)
- freg++;
- else
- {
- /* SysV ABI converts floats to doubles when placed in
- memory and requires 8 byte alignment */
- if (argstkspace & 0x4)
- argstkspace += 4;
- argstkspace += 8;
- }
- }
- else if (TYPE_CODE (type) == TYPE_CODE_INT && len == 8) /* long long */
- {
- if (greg > 9)
- {
- greg = 11;
- if (argstkspace & 0x4)
- argstkspace += 4;
- argstkspace += 8;
- }
- else
- {
- if ((greg & 1) == 0)
- greg++;
- greg += 2;
- }
- }
- else
- {
- if (len > 4
- || TYPE_CODE (type) == TYPE_CODE_STRUCT
- || TYPE_CODE (type) == TYPE_CODE_UNION)
- {
- /* Rounding to the nearest multiple of 8 may not be necessary,
- but it is safe. Particularly since we don't know the
- field types of the structure */
- structstkspace += round2 (len, 8);
- }
- if (greg <= 10)
- greg++;
- else
- argstkspace += 4;
- }
+ lmp = &lmo;
+
+ lmo.r_debug_size = 8; /* The actual size is 20 bytes, but
+ this is all we need. */
+ lmo.r_map_offset = 4;
+ lmo.r_map_size = 4;
+
+ lmo.link_map_size = 20; /* The actual size is 560 bytes, but
+ this is all we need. */
+ lmo.l_addr_offset = 0;
+ lmo.l_addr_size = 4;
+
+ lmo.l_name_offset = 4;
+ lmo.l_name_size = 4;
+
+ lmo.l_next_offset = 12;
+ lmo.l_next_size = 4;
+
+ lmo.l_prev_offset = 16;
+ lmo.l_prev_size = 4;
}
- /* Get current SP location */
- saved_sp = read_sp ();
+ return lmp;
+}
- sp -= argstkspace + structstkspace;
+enum {
+ ELF_NGREG = 48,
+ ELF_NFPREG = 33,
+ ELF_NVRREG = 33
+};
- /* Allocate space for backchain and callee's saved lr */
- sp -= 8;
+enum {
+ ELF_GREGSET_SIZE = (ELF_NGREG * 4),
+ ELF_FPREGSET_SIZE = (ELF_NFPREG * 8)
+};
- /* Make sure that we maintain 16 byte alignment */
- sp &= ~0x0f;
+void
+ppc_linux_supply_gregset (char *buf)
+{
+ int regi;
+ struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
+
+ for (regi = 0; regi < 32; regi++)
+ supply_register (regi, buf + 4 * regi);
+
+ supply_register (PC_REGNUM, buf + 4 * PPC_LINUX_PT_NIP);
+ supply_register (tdep->ppc_lr_regnum, buf + 4 * PPC_LINUX_PT_LNK);
+ supply_register (tdep->ppc_cr_regnum, buf + 4 * PPC_LINUX_PT_CCR);
+ supply_register (tdep->ppc_xer_regnum, buf + 4 * PPC_LINUX_PT_XER);
+ supply_register (tdep->ppc_ctr_regnum, buf + 4 * PPC_LINUX_PT_CTR);
+ if (tdep->ppc_mq_regnum != -1)
+ supply_register (tdep->ppc_mq_regnum, buf + 4 * PPC_LINUX_PT_MQ);
+ supply_register (tdep->ppc_ps_regnum, buf + 4 * PPC_LINUX_PT_MSR);
+}
+
+void
+ppc_linux_supply_fpregset (char *buf)
+{
+ int regi;
+ struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
- /* Update %sp before proceeding any further */
- write_register (SP_REGNUM, sp);
+ for (regi = 0; regi < 32; regi++)
+ supply_register (FP0_REGNUM + regi, buf + 8 * regi);
- /* write the backchain */
- store_address (old_sp_buf, 4, saved_sp);
- write_memory (sp, old_sp_buf, 4);
+ /* The FPSCR is stored in the low order word of the last doubleword in the
+ fpregset. */
+ supply_register (tdep->ppc_fpscr_regnum, buf + 8 * 32 + 4);
+}
- argoffset = 8;
- structoffset = argoffset + argstkspace;
- freg = 1;
- greg = 3;
- /* Now fill in the registers and stack... */
- for (argno = 0; argno < nargs; argno++)
+/*
+ Use a local version of this function to get the correct types for regsets.
+*/
+
+static void
+fetch_core_registers (char *core_reg_sect,
+ unsigned core_reg_size,
+ int which,
+ CORE_ADDR reg_addr)
+{
+ if (which == 0)
+ {
+ if (core_reg_size == ELF_GREGSET_SIZE)
+ ppc_linux_supply_gregset (core_reg_sect);
+ else
+ warning ("wrong size gregset struct in core file");
+ }
+ else if (which == 2)
{
- arg = args[argno];
- type = check_typedef (VALUE_TYPE (arg));
- len = TYPE_LENGTH (type);
-
- if (TYPE_CODE (type) == TYPE_CODE_FLT)
- {
- if (freg <= 8)
- {
- if (len > 8)
- printf_unfiltered (
- "Fatal Error: a floating point parameter #%d with a size > 8 is found!\n", argno);
- memcpy (®isters[REGISTER_BYTE (FP0_REGNUM + freg)],
- VALUE_CONTENTS (arg), len);
- freg++;
- }
- else
- {
- /* SysV ABI converts floats to doubles when placed in
- memory and requires 8 byte alignment */
- /* FIXME: Convert floats to doubles */
- if (argoffset & 0x4)
- argoffset += 4;
- write_memory (sp + argoffset, (char *) VALUE_CONTENTS (arg), len);
- argoffset += 8;
- }
- }
- else if (TYPE_CODE (type) == TYPE_CODE_INT && len == 8) /* long long */
- {
- if (greg > 9)
- {
- greg = 11;
- if (argoffset & 0x4)
- argoffset += 4;
- write_memory (sp + argoffset, (char *) VALUE_CONTENTS (arg), len);
- argoffset += 8;
- }
- else
- {
- if ((greg & 1) == 0)
- greg++;
-
- memcpy (®isters[REGISTER_BYTE (greg)],
- VALUE_CONTENTS (arg), 4);
- memcpy (®isters[REGISTER_BYTE (greg + 1)],
- VALUE_CONTENTS (arg) + 4, 4);
- greg += 2;
- }
- }
+ if (core_reg_size == ELF_FPREGSET_SIZE)
+ ppc_linux_supply_fpregset (core_reg_sect);
else
- {
- char val_buf[4];
- if (len > 4
- || TYPE_CODE (type) == TYPE_CODE_STRUCT
- || TYPE_CODE (type) == TYPE_CODE_UNION)
- {
- write_memory (sp + structoffset, VALUE_CONTENTS (arg), len);
- store_address (val_buf, 4, sp + structoffset);
- structoffset += round2 (len, 8);
- }
- else
- {
- memset (val_buf, 0, 4);
- memcpy (val_buf, VALUE_CONTENTS (arg), len);
- }
- if (greg <= 10)
- {
- *(int *) ®isters[REGISTER_BYTE (greg)] = 0;
- memcpy (®isters[REGISTER_BYTE (greg)], val_buf, 4);
- greg++;
- }
- else
- {
- write_memory (sp + argoffset, val_buf, 4);
- argoffset += 4;
- }
- }
+ warning ("wrong size fpregset struct in core file");
}
+}
+
+/* Register that we are able to handle ELF file formats using standard
+ procfs "regset" structures. */
+
+static struct core_fns ppc_linux_regset_core_fns =
+{
+ bfd_target_elf_flavour, /* core_flavour */
+ default_check_format, /* check_format */
+ default_core_sniffer, /* core_sniffer */
+ fetch_core_registers, /* core_read_registers */
+ NULL /* next */
+};
+
+static void
+ppc_linux_init_abi (struct gdbarch_info info,
+ struct gdbarch *gdbarch)
+{
+ struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
+
+ /* Until November 2001, gcc was not complying to the SYSV ABI for
+ returning structures less than or equal to 8 bytes in size. It was
+ returning everything in memory. When this was corrected, it wasn't
+ fixed for native platforms. */
+ set_gdbarch_use_struct_convention (gdbarch,
+ ppc_sysv_abi_broken_use_struct_convention);
- target_store_registers (-1);
- return sp;
+ if (tdep->wordsize == 4)
+ {
+ /* Note: kevinb/2002-04-12: See note in rs6000_gdbarch_init regarding
+ *_push_arguments(). The same remarks hold for the methods below. */
+ set_gdbarch_frameless_function_invocation (gdbarch,
+ ppc_linux_frameless_function_invocation);
+ set_gdbarch_frame_chain (gdbarch, ppc_linux_frame_chain);
+ set_gdbarch_frame_saved_pc (gdbarch, ppc_linux_frame_saved_pc);
+
+ set_gdbarch_frame_init_saved_regs (gdbarch,
+ ppc_linux_frame_init_saved_regs);
+ set_gdbarch_init_extra_frame_info (gdbarch,
+ ppc_linux_init_extra_frame_info);
+
+ set_gdbarch_memory_remove_breakpoint (gdbarch,
+ ppc_linux_memory_remove_breakpoint);
+ set_solib_svr4_fetch_link_map_offsets
+ (gdbarch, ppc_linux_svr4_fetch_link_map_offsets);
+ }
+}
+
+void
+_initialize_ppc_linux_tdep (void)
+{
+ gdbarch_register_osabi (bfd_arch_powerpc, GDB_OSABI_LINUX,
+ ppc_linux_init_abi);
+ add_core_fns (&ppc_linux_regset_core_fns);
}
projects / deliverable / binutils-gdb.git / blobdiff