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Commita7a7387

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Further improve code for probing the availability of ARM CRC instructions.
Andrew Gierth pointed out that commit1c72ec6 would yield the wronganswer on big-endian ARM systems, because the data being CRC'd would bedifferent. To fix that, and avoid the rather unsightly hard-wiredconstant, simply compare the hardware and software implementations'results.While we're at it, also log the resulting decision at DEBUG1, and errorout if the hw and sw results unexpectedly differ. Also, since thisfile must compile for both frontend and backend, avoid incorrectdependencies on backend-only headers.In passing, add a comment to postmaster.c about when the CRC functionpointer will get initialized.Thomas Munro, based on complaints from Andrew Gierth and Tom LaneDiscussion:https://postgr.es/m/HE1PR0801MB1323D171938EABC04FFE7FA9E3110@HE1PR0801MB1323.eurprd08.prod.outlook.com
1 parent30c66e7 commita7a7387

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2 files changed

+39
-8
lines changed

2 files changed

+39
-8
lines changed

‎src/backend/postmaster/postmaster.c

Lines changed: 9 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -957,7 +957,15 @@ PostmasterMain(int argc, char *argv[])
957957
*/
958958
CreateDataDirLockFile(true);
959959

960-
/* read control file (error checking and contains config) */
960+
/*
961+
* Read the control file (for error checking and config info).
962+
*
963+
* Since we verify the control file's CRC, this has a useful side effect
964+
* on machines where we need a run-time test for CRC support instructions.
965+
* The postmaster will do the test once at startup, and then its child
966+
* processes will inherit the correct function pointer and not need to
967+
* repeat the test.
968+
*/
961969
LocalProcessControlFile(false);
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963971
/*

‎src/port/pg_crc32c_armv8_choose.c

Lines changed: 30 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -18,11 +18,15 @@
1818
*-------------------------------------------------------------------------
1919
*/
2020

21-
#include"c.h"
21+
#ifndefFRONTEND
22+
#include"postgres.h"
23+
#else
24+
#include"postgres_fe.h"
25+
#endif
2226

2327
#include<setjmp.h>
28+
#include<signal.h>
2429

25-
#include"libpq/pqsignal.h"
2630
#include"port/pg_crc32c.h"
2731

2832

@@ -33,7 +37,7 @@ static sigjmp_buf illegal_instruction_jump;
3337
* isn't available, we expect to get SIGILL, which we can trap.
3438
*/
3539
staticvoid
36-
illegal_instruction_handler(intsigno)
40+
illegal_instruction_handler(SIGNAL_ARGS)
3741
{
3842
siglongjmp(illegal_instruction_jump,1);
3943
}
@@ -42,16 +46,35 @@ static bool
4246
pg_crc32c_armv8_available(void)
4347
{
4448
uint64data=42;
45-
boolresult;
49+
intresult;
4650

51+
/*
52+
* Be careful not to do anything that might throw an error while we have
53+
* the SIGILL handler set to a nonstandard value.
54+
*/
4755
pqsignal(SIGILL,illegal_instruction_handler);
4856
if (sigsetjmp(illegal_instruction_jump,1)==0)
49-
result= (pg_comp_crc32c_armv8(0,&data,sizeof(data))==0xdd439b0d);
57+
{
58+
/* Rather than hard-wiring an expected result, compare to SB8 code */
59+
result= (pg_comp_crc32c_armv8(0,&data,sizeof(data))==
60+
pg_comp_crc32c_sb8(0,&data,sizeof(data)));
61+
}
5062
else
51-
result= false;
63+
{
64+
/* We got the SIGILL trap */
65+
result=-1;
66+
}
5267
pqsignal(SIGILL,SIG_DFL);
5368

54-
returnresult;
69+
#ifndefFRONTEND
70+
/* We don't expect this case, so complain loudly */
71+
if (result==0)
72+
elog(ERROR,"crc32 hardware and software results disagree");
73+
74+
elog(DEBUG1,"using armv8 crc32 hardware = %d", (result>0));
75+
#endif
76+
77+
return (result>0);
5578
}
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5780
/*

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