Messages in this thread | | | Subject | Re: [PATCH v2 1/3] perf tools: Use offset instead of dwarfnum in register table. | From | Hekuang <> | Date | Sat, 4 Feb 2017 17:03:20 +0800 |
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hi
在 2017/2/3 21:00, Will Deacon 写道: > On Fri, Feb 03, 2017 at 11:06:05AM +0000, He Kuang wrote: >> This patch changes the 'dwarfnum' to 'offset' in register table, so >> the index of array becomes the dwarfnum (the index of each register >> defined by DWARF) and the "offset" member means the byte-offset of the >> register in (user_)pt_regs. This change makes the code consistent with >> x86. >> >> Acked-by: Masami Hiramatsu <mhiramat@kernel.org> >> Signed-off-by: He Kuang <hekuang@huawei.com> >> --- >> tools/perf/arch/arm64/util/dwarf-regs.c | 107 ++++++++++++++++---------------- >> 1 file changed, 52 insertions(+), 55 deletions(-) > Thanks for splitting this up. Comment below. > >> diff --git a/tools/perf/arch/arm64/util/dwarf-regs.c b/tools/perf/arch/arm64/util/dwarf-regs.c >> index d49efeb..090f36b 100644 >> --- a/tools/perf/arch/arm64/util/dwarf-regs.c >> +++ b/tools/perf/arch/arm64/util/dwarf-regs.c >> @@ -9,72 +9,69 @@ >> */ >> >> #include <stddef.h> >> +#include <linux/ptrace.h> /* for struct user_pt_regs */ >> #include <dwarf-regs.h> >> >> -struct pt_regs_dwarfnum { >> +struct pt_regs_offset { >> const char *name; >> - unsigned int dwarfnum; >> + int offset; >> }; >> >> -#define STR(s) #s >> -#define REG_DWARFNUM_NAME(r, num) {.name = r, .dwarfnum = num} >> -#define GPR_DWARFNUM_NAME(num) \ >> - {.name = STR(%x##num), .dwarfnum = num} >> -#define REG_DWARFNUM_END {.name = NULL, .dwarfnum = 0} >> - >> /* >> * Reference: >> * http://infocenter.arm.com/help/topic/com.arm.doc.ihi0057b/IHI0057B_aadwarf64.pdf >> */ >> -static const struct pt_regs_dwarfnum regdwarfnum_table[] = { >> - GPR_DWARFNUM_NAME(0), >> - GPR_DWARFNUM_NAME(1), >> - GPR_DWARFNUM_NAME(2), >> - GPR_DWARFNUM_NAME(3), >> - GPR_DWARFNUM_NAME(4), >> - GPR_DWARFNUM_NAME(5), >> - GPR_DWARFNUM_NAME(6), >> - GPR_DWARFNUM_NAME(7), >> - GPR_DWARFNUM_NAME(8), >> - GPR_DWARFNUM_NAME(9), >> - GPR_DWARFNUM_NAME(10), >> - GPR_DWARFNUM_NAME(11), >> - GPR_DWARFNUM_NAME(12), >> - GPR_DWARFNUM_NAME(13), >> - GPR_DWARFNUM_NAME(14), >> - GPR_DWARFNUM_NAME(15), >> - GPR_DWARFNUM_NAME(16), >> - GPR_DWARFNUM_NAME(17), >> - GPR_DWARFNUM_NAME(18), >> - GPR_DWARFNUM_NAME(19), >> - GPR_DWARFNUM_NAME(20), >> - GPR_DWARFNUM_NAME(21), >> - GPR_DWARFNUM_NAME(22), >> - GPR_DWARFNUM_NAME(23), >> - GPR_DWARFNUM_NAME(24), >> - GPR_DWARFNUM_NAME(25), >> - GPR_DWARFNUM_NAME(26), >> - GPR_DWARFNUM_NAME(27), >> - GPR_DWARFNUM_NAME(28), >> - GPR_DWARFNUM_NAME(29), >> - REG_DWARFNUM_NAME("%lr", 30), >> - REG_DWARFNUM_NAME("%sp", 31), >> - REG_DWARFNUM_END, >> -}; >> +#define REG_OFFSET_NAME(r, num) {.name = "%" #r, \ >> + .offset = offsetof(struct user_pt_regs, regs[num])} > Whilst this works in practice, this is undefined behaviour for "sp", since > you'll go off the end of the regs array.
It's not undefined behaviour here, struct user_pt_regs { __u64 regs[31]; __u64 sp; __u64 pc; __u64 pstate; }; user_pt_regs->regs[31] is user_pt_regs->sp and the offset value is correct. > > I still think you're better off sticking with the dwarfnum, then just having > a dwarfnum2offset macro that multiplies by the size of a register. > > Will I think add a ptregs_offset field is more suitable and makes the code indepent to struct user_pt_regs layout, for example if the structure changed to this:
struct user_pt_regs { __u64 sp; __u64 pc; __u64 pstate; __u64 regs[31]; };
The multiply result will be incorrect. Patch updated and the change is similar to commit "4679bccaa308" (perf tools powerpc: Add support for generating bpf prologue)
Please review, thanks.
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