Cygwin IPC - ftok() returns negative values - Bug Report
Stanisław Wawszczak
stanislaw.wawszczak@iscg.pl
Wed Jun 29 13:36:00 GMT 2016
Dear All,
I have had to compile sblim-sfcbd-1.4.10 on Cygwin. It is using IPC semaphores.
Unfortunately it is returning wrong value as the result of complicated bit-wise logical operations.
I have tried to “hack the system” and make multiplication of returned value by -1, but it triggers error in semget()
Environment:
Windows 2012 R2 with latest patches
I have installed Cygwin from official installer couple days ago.
I have attached the gdb session from such invocation. You can see the path and id in arguments are correct and stat() function returns correct values.
Finally result in %rax is negative:
rax 0xaf0b000701cc1d53 -5833568862233420461
Best Regards,
Stanislaw Wawszczak
Iscg Poland
###############################################################
# GDB session
###############################################################
Breakpoint 1, ftok (path=0x4b11f1912 <nls+666> "/usr/local/sbin/sfcbd.exe", id=83) at /usr/src/debug/cygwin-2.5.2-1/winsup/cygwin/ipc.cc:18
18 {
(gdb) x/5i
0x4b1201438 <sfcbSockets>: (bad)
0x4b1201439 <sfcbSockets+1>: add %al,(%rax)
0x4b120143b <sfcbSockets+3>: add %al,(%rdi)
0x4b120143d <sfcbSockets+5>: add %al,(%rax)
0x4b120143f <sfcbSockets+7>: add %al,(%rbx)
(gdb) x/5i
0x4b1201441 <resultSockets+1>: add %al,(%rax)
0x4b1201443 <resultSockets+3>: add %al,0x0(%rip) # 0x4b1201449 <ptBase+1>
0x4b1201449 <ptBase+1>: add %al,(%rax)
0x4b120144b <ptBase+3>: add %al,(%rax)
0x4b120144d <stBase+1>: add %al,(%rax)
(gdb) x/5i $pc
=> 0x1800c6e50 <ftok(char const*, int)>: push %rbx
0x1800c6e51 <ftok(char const*, int)+1>: sub $0xa0,%rsp
0x1800c6e58 <ftok(char const*, int)+8>: mov %edx,%ebx
0x1800c6e5a <ftok(char const*, int)+10>: lea 0x20(%rsp),%rdx
0x1800c6e5f <ftok(char const*, int)+15>: callq 0x180144970 <stat64(char const*, stat*)>
(gdb) x/5i
0x1800c6e64 <ftok(char const*, int)+20>: test %eax,%eax
0x1800c6e66 <ftok(char const*, int)+22>: jne 0x1800c6ec0 <ftok(char const*, int)+112>
0x1800c6e68 <ftok(char const*, int)+24>: mov 0x20(%rsp),%edx
0x1800c6e6c <ftok(char const*, int)+28>: mov 0x28(%rsp),%r8
0x1800c6e71 <ftok(char const*, int)+33>: mov %edx,%eax
(gdb) x/5i
0x1800c6e73 <ftok(char const*, int)+35>: movzbl %dl,%edx
0x1800c6e76 <ftok(char const*, int)+38>: and $0xff0000,%eax
0x1800c6e7b <ftok(char const*, int)+43>: shl $0x30,%rdx
0x1800c6e7f <ftok(char const*, int)+47>: shl $0x28,%rax
0x1800c6e83 <ftok(char const*, int)+51>: or %rdx,%rax
(gdb) x/5i
0x1800c6e86 <ftok(char const*, int)+54>: movabs $0xffffc00000000000,%rdx
0x1800c6e90 <ftok(char const*, int)+64>: and %r8,%rdx
0x1800c6e93 <ftok(char const*, int)+67>: and $0x3fffff,%r8d
0x1800c6e9a <ftok(char const*, int)+74>: shr $0x10,%rdx
0x1800c6e9e <ftok(char const*, int)+78>: shl $0x8,%r8
(gdb) x/5i
0x1800c6ea2 <ftok(char const*, int)+82>: or %rdx,%rax
0x1800c6ea5 <ftok(char const*, int)+85>: mov %rax,%rcx
0x1800c6ea8 <ftok(char const*, int)+88>: movzbl %bl,%eax
0x1800c6eab <ftok(char const*, int)+91>: or %r8,%rax
0x1800c6eae <ftok(char const*, int)+94>: or %rcx,%rax
(gdb) x/5i
0x1800c6eb1 <ftok(char const*, int)+97>: add $0xa0,%rsp
0x1800c6eb8 <ftok(char const*, int)+104>: pop %rbx
0x1800c6eb9 <ftok(char const*, int)+105>: retq
0x1800c6eba <ftok(char const*, int)+106>: nopw 0x0(%rax,%rax,1)
0x1800c6ec0 <ftok(char const*, int)+112>: mov $0xffffffffffffffff,%rax
(gdb) x/5i
0x1800c6ec7 <ftok(char const*, int)+119>: jmp 0x1800c6eb1 <ftok(char const*, int)+97>
0x1800c6ec9 <ftok+121>: nop
0x1800c6eca <ftok+122>: nop
0x1800c6ecb <ftok+123>: nop
0x1800c6ecc <ftok+124>: nop
(gdb) ni
0x00000001800c6e51 18 {
(gdb) ni
18 {
(gdb) ni
21 if (stat64 (path, &statbuf))
(gdb) x/5i $pc
=> 0x1800c6e5a <ftok(char const*, int)+10>: lea 0x20(%rsp),%rdx
0x1800c6e5f <ftok(char const*, int)+15>: callq 0x180144970 <stat64(char const*, stat*)>
0x1800c6e64 <ftok(char const*, int)+20>: test %eax,%eax
0x1800c6e66 <ftok(char const*, int)+22>: jne 0x1800c6ec0 <ftok(char const*, int)+112>
0x1800c6e68 <ftok(char const*, int)+24>: mov 0x20(%rsp),%edx
(gdb) ni
0x00000001800c6e5f 21 if (stat64 (path, &statbuf))
(gdb) x/5i $pc
=> 0x1800c6e5f <ftok(char const*, int)+15>: callq 0x180144970 <stat64(char const*, stat*)>
0x1800c6e64 <ftok(char const*, int)+20>: test %eax,%eax
0x1800c6e66 <ftok(char const*, int)+22>: jne 0x1800c6ec0 <ftok(char const*, int)+112>
0x1800c6e68 <ftok(char const*, int)+24>: mov 0x20(%rsp),%edx
0x1800c6e6c <ftok(char const*, int)+28>: mov 0x28(%rsp),%r8
(gdb) ni
0x00000001800c6e64 21 if (stat64 (path, &statbuf))
(gdb) x/5i $pc
=> 0x1800c6e64 <ftok(char const*, int)+20>: test %eax,%eax
0x1800c6e66 <ftok(char const*, int)+22>: jne 0x1800c6ec0 <ftok(char const*, int)+112>
0x1800c6e68 <ftok(char const*, int)+24>: mov 0x20(%rsp),%edx
0x1800c6e6c <ftok(char const*, int)+28>: mov 0x28(%rsp),%r8
0x1800c6e71 <ftok(char const*, int)+33>: mov %edx,%eax
(gdb) r %eax
The program being debugged has been started already.
Start it from the beginning? (y or n) n
Program not restarted.
(gdb) info registers
rax 0x0 0
rbx 0x53 83
rcx 0x7ffa7b5dac7a 140713788288122 rdx 0x0 0 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0xffffc768 4294952808
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6e64 0x1800c6e64 <ftok(char const*, int)+20> eflags 0x202 [ IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) ni
0x00000001800c6e66 21 if (stat64 (path, &statbuf))
(gdb) r %eax
The program being debugged has been started already.
Start it from the beginning? (y or n) n
Program not restarted.
(gdb) x/5i $pc
=> 0x1800c6e66 <ftok(char const*, int)+22>: jne 0x1800c6ec0 <ftok(char const*, int)+112>
0x1800c6e68 <ftok(char const*, int)+24>: mov 0x20(%rsp),%edx
0x1800c6e6c <ftok(char const*, int)+28>: mov 0x28(%rsp),%r8
0x1800c6e71 <ftok(char const*, int)+33>: mov %edx,%eax
0x1800c6e73 <ftok(char const*, int)+35>: movzbl %dl,%edx
(gdb) ni
78 tmp = (((key_t) statbuf.st_dev) & 0x0000000000ff0000LL) << 40;
(gdb) print 0x20(%rsp
A syntax error in expression, near `%rsp'.
(gdb) print 0x20(%rsp)
A syntax error in expression, near `%rsp)'.
(gdb) ni
83 tmp |= (((key_t) statbuf.st_ino) & 0xffffc00000000000LL) >> 16;
(gdb) x/5i $pc
=> 0x1800c6e6c <ftok(char const*, int)+28>: mov 0x28(%rsp),%r8
0x1800c6e71 <ftok(char const*, int)+33>: mov %edx,%eax
0x1800c6e73 <ftok(char const*, int)+35>: movzbl %dl,%edx
0x1800c6e76 <ftok(char const*, int)+38>: and $0xff0000,%eax
0x1800c6e7b <ftok(char const*, int)+43>: shl $0x30,%rdx
(gdb) info registers
rax 0x0 0
rbx 0x53 83
rcx 0x7ffa7b5dac7a 140713788288122 rdx 0x7eafb40b 2125444107 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0xffffc768 4294952808
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6e6c 0x1800c6e6c <ftok(char const*, int)+28> eflags 0x246 [ PF ZF IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) ni
78 tmp = (((key_t) statbuf.st_dev) & 0x0000000000ff0000LL) << 40;
(gdb) x/5i $pc
=> 0x1800c6e71 <ftok(char const*, int)+33>: mov %edx,%eax
0x1800c6e73 <ftok(char const*, int)+35>: movzbl %dl,%edx
0x1800c6e76 <ftok(char const*, int)+38>: and $0xff0000,%eax
0x1800c6e7b <ftok(char const*, int)+43>: shl $0x30,%rdx
0x1800c6e7f <ftok(char const*, int)+47>: shl $0x28,%rax
(gdb) ni
83 tmp |= (((key_t) statbuf.st_ino) & 0xffffc00000000000LL) >> 16;
(gdb) x/5i $pc
=> 0x1800c6e73 <ftok(char const*, int)+35>: movzbl %dl,%edx
0x1800c6e76 <ftok(char const*, int)+38>: and $0xff0000,%eax
0x1800c6e7b <ftok(char const*, int)+43>: shl $0x30,%rdx
0x1800c6e7f <ftok(char const*, int)+47>: shl $0x28,%rax
0x1800c6e83 <ftok(char const*, int)+51>: or %rdx,%rax
(gdb) info registers
rax 0x7eafb40b 2125444107 rbx 0x53 83 rcx 0x7ffa7b5dac7a 140713788288122 rdx 0x7eafb40b 2125444107 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0x700000001cc1d 1970324837092381
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6e73 0x1800c6e73 <ftok(char const*, int)+35> eflags 0x246 [ PF ZF IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) ni
78 tmp = (((key_t) statbuf.st_dev) & 0x0000000000ff0000LL) << 40;
(gdb) info registers
rax 0x7eafb40b 2125444107 rbx 0x53 83 rcx 0x7ffa7b5dac7a 140713788288122 rdx 0xb 11 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0x700000001cc1d 1970324837092381
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6e76 0x1800c6e76 <ftok(char const*, int)+38> eflags 0x246 [ PF ZF IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) x/5i $pc
=> 0x1800c6e76 <ftok(char const*, int)+38>: and $0xff0000,%eax
0x1800c6e7b <ftok(char const*, int)+43>: shl $0x30,%rdx
0x1800c6e7f <ftok(char const*, int)+47>: shl $0x28,%rax
0x1800c6e83 <ftok(char const*, int)+51>: or %rdx,%rax
0x1800c6e86 <ftok(char const*, int)+54>: movabs $0xffffc00000000000,%rdx
(gdb) ni; x/5i $pc; info registers
Invalid character ';' in expression.
(gdb) ni
83 tmp |= (((key_t) statbuf.st_ino) & 0xffffc00000000000LL) >> 16;
(gdb) x/5i $pc
=> 0x1800c6e7b <ftok(char const*, int)+43>: shl $0x30,%rdx
0x1800c6e7f <ftok(char const*, int)+47>: shl $0x28,%rax
0x1800c6e83 <ftok(char const*, int)+51>: or %rdx,%rax
0x1800c6e86 <ftok(char const*, int)+54>: movabs $0xffffc00000000000,%rdx
0x1800c6e90 <ftok(char const*, int)+64>: and %r8,%rdx
(gdb) info registers
rax 0xaf0000 11468800
rbx 0x53 83
rcx 0x7ffa7b5dac7a 140713788288122 rdx 0xb 11 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0x700000001cc1d 1970324837092381
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6e7b 0x1800c6e7b <ftok(char const*, int)+43> eflags 0x206 [ PF IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) ni
78 tmp = (((key_t) statbuf.st_dev) & 0x0000000000ff0000LL) << 40;
(gdb) info registers
rax 0xaf0000 11468800
rbx 0x53 83
rcx 0x7ffa7b5dac7a 140713788288122 rdx 0xb000000000000 3096224743817216 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0x700000001cc1d 1970324837092381
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6e7f 0x1800c6e7f <ftok(char const*, int)+47> eflags 0x206 [ PF IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) x/5i $pc
=> 0x1800c6e7f <ftok(char const*, int)+47>: shl $0x28,%rax
0x1800c6e83 <ftok(char const*, int)+51>: or %rdx,%rax
0x1800c6e86 <ftok(char const*, int)+54>: movabs $0xffffc00000000000,%rdx
0x1800c6e90 <ftok(char const*, int)+64>: and %r8,%rdx
0x1800c6e93 <ftok(char const*, int)+67>: and $0x3fffff,%r8d
(gdb) ni
83 tmp |= (((key_t) statbuf.st_ino) & 0xffffc00000000000LL) >> 16;
(gdb) x/5i $pc
=> 0x1800c6e83 <ftok(char const*, int)+51>: or %rdx,%rax
0x1800c6e86 <ftok(char const*, int)+54>: movabs $0xffffc00000000000,%rdx
0x1800c6e90 <ftok(char const*, int)+64>: and %r8,%rdx
0x1800c6e93 <ftok(char const*, int)+67>: and $0x3fffff,%r8d
0x1800c6e9a <ftok(char const*, int)+74>: shr $0x10,%rdx
(gdb) info registers
rax 0xaf00000000000000 -5836665117072162816 rbx 0x53 83 rcx 0x7ffa7b5dac7a 140713788288122 rdx 0xb000000000000 3096224743817216 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0x700000001cc1d 1970324837092381
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6e83 0x1800c6e83 <ftok(char const*, int)+51> eflags 0x286 [ PF SF IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) ni
0x00000001800c6e86 83 tmp |= (((key_t) statbuf.st_ino) & 0xffffc00000000000LL) >> 16;
(gdb) x/5i $pc
=> 0x1800c6e86 <ftok(char const*, int)+54>: movabs $0xffffc00000000000,%rdx
0x1800c6e90 <ftok(char const*, int)+64>: and %r8,%rdx
0x1800c6e93 <ftok(char const*, int)+67>: and $0x3fffff,%r8d
0x1800c6e9a <ftok(char const*, int)+74>: shr $0x10,%rdx
0x1800c6e9e <ftok(char const*, int)+78>: shl $0x8,%r8
(gdb) info registers
rax 0xaf0b000000000000 -5833568892328345600 rbx 0x53 83 rcx 0x7ffa7b5dac7a 140713788288122 rdx 0xb000000000000 3096224743817216 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0x700000001cc1d 1970324837092381
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6e86 0x1800c6e86 <ftok(char const*, int)+54> eflags 0x286 [ PF SF IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) ni
0x00000001800c6e90 83 tmp |= (((key_t) statbuf.st_ino) & 0xffffc00000000000LL) >> 16;
(gdb) info registers
rax 0xaf0b000000000000 -5833568892328345600 rbx 0x53 83 rcx 0x7ffa7b5dac7a 140713788288122 rdx 0xffffc00000000000 -70368744177664 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0x700000001cc1d 1970324837092381
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6e90 0x1800c6e90 <ftok(char const*, int)+64> eflags 0x286 [ PF SF IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) ni
0x00000001800c6e93 83 tmp |= (((key_t) statbuf.st_ino) & 0xffffc00000000000LL) >> 16;
(gdb) x/5i $pc
=> 0x1800c6e93 <ftok(char const*, int)+67>: and $0x3fffff,%r8d
0x1800c6e9a <ftok(char const*, int)+74>: shr $0x10,%rdx
0x1800c6e9e <ftok(char const*, int)+78>: shl $0x8,%r8
0x1800c6ea2 <ftok(char const*, int)+82>: or %rdx,%rax
0x1800c6ea5 <ftok(char const*, int)+85>: mov %rax,%rcx
(gdb) info registers
rax 0xaf0b000000000000 -5833568892328345600 rbx 0x53 83 rcx 0x7ffa7b5dac7a 140713788288122 rdx 0x7000000000000 1970324836974592 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0x700000001cc1d 1970324837092381
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6e93 0x1800c6e93 <ftok(char const*, int)+67> eflags 0x206 [ PF IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) ni
0x00000001800c6e9a 83 tmp |= (((key_t) statbuf.st_ino) & 0xffffc00000000000LL) >> 16;
(gdb) ni
0x00000001800c6e9e 83 tmp |= (((key_t) statbuf.st_ino) & 0xffffc00000000000LL) >> 16;
(gdb) info registers
rax 0xaf0b000000000000 -5833568892328345600 rbx 0x53 83 rcx 0x7ffa7b5dac7a 140713788288122 rdx 0x700000000 30064771072 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0x1cc1d 117789
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6e9e 0x1800c6e9e <ftok(char const*, int)+78> eflags 0x206 [ PF IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) ni
0x00000001800c6ea2 83 tmp |= (((key_t) statbuf.st_ino) & 0xffffc00000000000LL) >> 16;
(gdb) ni
0x00000001800c6ea5 83 tmp |= (((key_t) statbuf.st_ino) & 0xffffc00000000000LL) >> 16;
(gdb) info registers
rax 0xaf0b000700000000 -5833568862263574528 rbx 0x53 83 rcx 0x7ffa7b5dac7a 140713788288122 rdx 0x700000000 30064771072 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0x1cc1d00 30153984
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6ea5 0x1800c6ea5 <ftok(char const*, int)+85> eflags 0x286 [ PF SF IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) x/5i $pc
=> 0x1800c6ea5 <ftok(char const*, int)+85>: mov %rax,%rcx
0x1800c6ea8 <ftok(char const*, int)+88>: movzbl %bl,%eax
0x1800c6eab <ftok(char const*, int)+91>: or %r8,%rax
0x1800c6eae <ftok(char const*, int)+94>: or %rcx,%rax
0x1800c6eb1 <ftok(char const*, int)+97>: add $0xa0,%rsp
(gdb) ni
0x00000001800c6ea8 83 tmp |= (((key_t) statbuf.st_ino) & 0xffffc00000000000LL) >> 16;
(gdb) x/5i $pc
=> 0x1800c6ea8 <ftok(char const*, int)+88>: movzbl %bl,%eax
0x1800c6eab <ftok(char const*, int)+91>: or %r8,%rax
0x1800c6eae <ftok(char const*, int)+94>: or %rcx,%rax
0x1800c6eb1 <ftok(char const*, int)+97>: add $0xa0,%rsp
0x1800c6eb8 <ftok(char const*, int)+104>: pop %rbx
(gdb) info registers
rax 0xaf0b000700000000 -5833568862263574528 rbx 0x53 83 rcx 0xaf0b000700000000 -5833568862263574528 rdx 0x700000000 30064771072 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0x1cc1d00 30153984
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6ea8 0x1800c6ea8 <ftok(char const*, int)+88> eflags 0x286 [ PF SF IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) ni
0x00000001800c6eab 83 tmp |= (((key_t) statbuf.st_ino) & 0xffffc00000000000LL) >> 16;
(gdb) info registers
rax 0x53 83
rbx 0x53 83
rcx 0xaf0b000700000000 -5833568862263574528 rdx 0x700000000 30064771072 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0x1cc1d00 30153984
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6eab 0x1800c6eab <ftok(char const*, int)+91> eflags 0x286 [ PF SF IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) ni
0x00000001800c6eae 83 tmp |= (((key_t) statbuf.st_ino) & 0xffffc00000000000LL) >> 16;
(gdb) info registers
rax 0x1cc1d53 30154067 rbx 0x53 83 rcx 0xaf0b000700000000 -5833568862263574528 rdx 0x700000000 30064771072 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0x1cc1d00 30153984
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6eae 0x1800c6eae <ftok(char const*, int)+94> eflags 0x206 [ PF IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) x/5i $pc
=> 0x1800c6eae <ftok(char const*, int)+94>: or %rcx,%rax
0x1800c6eb1 <ftok(char const*, int)+97>: add $0xa0,%rsp
0x1800c6eb8 <ftok(char const*, int)+104>: pop %rbx
0x1800c6eb9 <ftok(char const*, int)+105>: retq
0x1800c6eba <ftok(char const*, int)+106>: nopw 0x0(%rax,%rax,1)
(gdb) info registers
rax 0x1cc1d53 30154067 rbx 0x53 83 rcx 0xaf0b000700000000 -5833568862263574528 rdx 0x700000000 30064771072 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0x1cc1d00 30153984
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6eae 0x1800c6eae <ftok(char const*, int)+94> eflags 0x206 [ PF IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) ni
89 }
(gdb) info registers
rax 0xaf0b000701cc1d53 -5833568862233420461 rbx 0x53 83 rcx 0xaf0b000700000000 -5833568862263574528 rdx 0x700000000 30064771072 rsi 0x4 4 rdi 0x10040596e 4299184494 rbp 0x4b1201464 0x4b1201464 <labelProcs> rsp 0xffffc930 0xffffc930
r8 0x1cc1d00 30153984
r9 0x4b1201464 20151538788
r10 0x0 0
r11 0x203 515
r12 0x4b11ef0c0 20151464128
r13 0x20 32
r14 0x0 0
r15 0x5 5
rip 0x1800c6eb1 0x1800c6eb1 <ftok(char const*, int)+97> eflags 0x286 [ PF SF IF ] cs 0x33 51 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x53 83 gs 0x2b 43
(gdb) ni
0x00000001800c6eb8 89 }
(gdb) x/5i $pc
=> 0x1800c6eb8 <ftok(char const*, int)+104>: pop %rbx
0x1800c6eb9 <ftok(char const*, int)+105>: retq
0x1800c6eba <ftok(char const*, int)+106>: nopw 0x0(%rax,%rax,1)
0x1800c6ec0 <ftok(char const*, int)+112>: mov $0xffffffffffffffff,%rax
0x1800c6ec7 <ftok(char const*, int)+119>: jmp 0x1800c6eb1 <ftok(char const*, int)+97>
(gdb) ni
0x00000001800c6eb9 89 }
(gdb) n
##############################################################
# ftok() C source from debugger
##############################################################
/* ipc.cc: Single unix specification IPC interface for Cygwin
Originally written by Robert Collins <robert.collins@hotmail.com>
Updated to 64 bit key_t by Charles Wilson <cygwin@cwilson.fastmail.fm>
This file is part of Cygwin.
This software is a copyrighted work licensed under the terms of the
Cygwin license. Please consult the file "CYGWIN_LICENSE" for
details. */
#include "winsup.h"
#include <sys/stat.h>
/* Notes: we return a valid key even if id's low order 8 bits are 0. */ extern "C" key_t ftok (const char *path, int id) {
struct stat statbuf;
key_t tmp;
if (stat64 (path, &statbuf))
{
/* stat set the appropriate errno for us */
return (key_t) -1;
}
/* Since Cygwin 1.5
dev_t is 32bits for cygwin
ino_t is 64bits for cygwin
and we need 8 bits for the id.
thus key_t needs 104 bits total -- but we only have 64 (long long)
We will have to alias; leaving open the possibility that the same
key will be returned for multiple files. This possibility exists
also on Linux; the question is, how to minimize this possibility.
How to solve? Well, based on C. Vinschen's research, the nFileIndex*
words vary as follows, on a partition with > 110,000 files
nFileIndexHigh: 564 values between 0x00010000 -- 0xffff0000
nFileIndexLow : 103812 values between 0x00000000 -- 0x0003ffff
R. Collins suggests that these may represent a tree path,
and that it would require ~2.9M files to force the tree depth
to increase and reveal more bit usage.
Implementation details: dev_t is 32bits, but is formed by
device(32bits) << 16 | unit(32bits)
But device is ACTUALLY == status & FH_DEVMASK, where FH_DEVMASK
is 0x00000fff --> 12 bits
As it happens, the maximum number of devices is actually
FH_NDEV, not FH_DEVMASK, where FH_NDEV is currently 0x0000001d.
However, FH_NDEV grows as new device types are added. So
currently the device number needs 5 bits, but later? Let's
take a cue from Linux, and use the lower 8 bits (instead of the
lower 12 or 16) for the device (major?) number.
Similarly, while 'units' is an int (32bits), it is unclear
how many of these are significant. For most devices, it seems that
'units' is equivalent to 'minor'. For FH_TAPE, it's obvious that
only 8 bits are important. However, for FH_SOCKET...it might be
as high as 16 significant bits.
Let's assume that we only need 8 bits from device (major) and
only 8 bits from unit (minor). (On linux, only 8 bits of minor
are used, and none from major).
---> so, we only need 0x00ff00ff (16 bits) of dev_t
---> we MUST have all 8 bits of id.
---> So, we only have 64 - 8 - 16 = 40 bits for ino_t. But, we
need 0xffff0000 for nFileIndexHigh and 0x0003ffff for nFileIndexLow
minimum, or 16 + 18 = 34 bits. Lucky us - we have 6 more bits
to distribute.
For lack of a better idea, we'll allocate 2 of the extra bits to
nFileIndexHigh and 4 to nFileIndexLow. */
/* get 8 bits from dev_t (major), put into 0xff00000000000000L */
tmp = (((key_t) statbuf.st_dev) & 0x0000000000ff0000LL) << 40;
/* get 8 bits from dev_t (minor), put into 0x00ff000000000000L */
tmp |= (((key_t) statbuf.st_dev) & 0x00000000000000ffLL) << 48;
/* get upper 16+2 bits from nFileInfoHigh, put into 0x0000ffffc0000000L
shift down first, then mask, to avoid sign extension on rightshift */
tmp |= (((key_t) statbuf.st_ino) & 0xffffc00000000000LL) >> 16;
/* get lower 18+4 bits from nFileInfoLow, put into 0x000000003fffff00L */
tmp |= (((key_t) statbuf.st_ino) & 0x00000000003fffffLL) << 8;
/* use all 8 bits of id, and put into 0x00000000000000ffL */
tmp |= (id & 0x00ff);
return tmp;
}
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