Be stricter on which functions we can probe with FBT. We now only check the
first instruction to see if it's either a pushm with lr, or a sub with sp. The former is the common case, with the latter used with va_args. This removes 12 probes. These are all hand-written assembly, with a few C functions with no stack usage. Submitted by: Howard Su <howard0su@gmail.com> Differential Revision: https://reviews.freebsd.org/D4419
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svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=292663
@ -35,6 +35,7 @@
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#include <sys/param.h>
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#include <sys/dtrace.h>
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#include <machine/stack.h>
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#include <machine/trap.h>
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#include "fbt.h"
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@ -42,6 +43,7 @@
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#define FBT_PUSHM 0xe92d0000
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#define FBT_POPM 0xe8bd0000
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#define FBT_JUMP 0xea000000
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#define FBT_SUBSP 0xe24dd000
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#define FBT_ENTRY "entry"
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#define FBT_RETURN "return"
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@ -111,12 +113,18 @@ fbt_provide_module_function(linker_file_t lf, int symindx,
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instr = (uint32_t *)symval->value;
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limit = (uint32_t *)(symval->value + symval->size);
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for (; instr < limit; instr++)
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if ((*instr & 0xffff0000) == FBT_PUSHM &&
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(*instr & 0x4000) != 0)
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break;
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/*
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* va_arg functions has first instruction of
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* sub sp, sp, #?
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*/
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if ((*instr & 0xfffff000) == FBT_SUBSP)
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instr++;
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if (instr >= limit)
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/*
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* check if insn is a pushm with LR
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*/
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if ((*instr & 0xffff0000) != FBT_PUSHM ||
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(*instr & (1 << LR)) == 0)
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return (0);
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fbt = malloc(sizeof (fbt_probe_t), M_FBT, M_WAITOK | M_ZERO);
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