From: Peter Zijlstra <peterz@infradead.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
mark.rutland@arm.com, dvyukov@google.com, seanjc@google.com,
pbonzini@redhat.com, mbenes@suse.cz
Subject: Re: [RFC][PATCH 07/22] x86,extable: Extend extable functionality
Date: Fri, 5 Nov 2021 08:54:00 +0100 [thread overview]
Message-ID: <20211105075400.GG174703@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20211104214935.xl54xlr3snwmtyna@treble>
On Thu, Nov 04, 2021 at 02:49:35PM -0700, Josh Poimboeuf wrote:
> On Thu, Nov 04, 2021 at 05:47:36PM +0100, Peter Zijlstra wrote:
> > +asm(
> > +" .macro extable_type_reg type:req reg:req\n"
> > +" .set regnr, 0\n"
> > +" .irp rs,rax,rcx,rdx,rbx,rsp,rbp,rsi,rdi,r8,r9,r10,r11,r12,r13,r14,r15\n"
> > +" .ifc \\reg, %\\rs\n"
> > +" .long \\type + (regnr << 8)\n"
> > +" .endif\n"
> > +" .set regnr, regnr+1\n"
> > +" .endr\n"
> > +" .set regnr, 0\n"
> > +" .irp rs,eax,ecx,edx,ebx,esp,ebp,esi,edi,r8d,r9d,r10d,r11d,r12d,r13d,r14d,r15d\n"
> > +" .ifc \\reg, %\\rs\n"
> > +" .long \\type + (regnr << 8)\n"
> > +" .endif\n"
> > +" .set regnr, regnr+1\n"
> > +" .endr\n"
> > +" .endm\n"
> > +);
>
> How about some error checking to detect a typo, or a forgotten '%':
>
> diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
> index 5d0ff8c60983..95bb23082b87 100644
> --- a/arch/x86/include/asm/asm.h
> +++ b/arch/x86/include/asm/asm.h
> @@ -154,9 +154,11 @@
>
> asm(
> " .macro extable_type_reg type:req reg:req\n"
> +" .set found, 0\n"
> " .set regnr, 0\n"
> " .irp rs,rax,rcx,rdx,rbx,rsp,rbp,rsi,rdi,r8,r9,r10,r11,r12,r13,r14,r15\n"
> " .ifc \\reg, %\\rs\n"
> +" .set found, found+1\n"
> " .long \\type + (regnr << 8)\n"
> " .endif\n"
> " .set regnr, regnr+1\n"
> @@ -164,10 +166,14 @@ asm(
> " .set regnr, 0\n"
> " .irp rs,eax,ecx,edx,ebx,esp,ebp,esi,edi,r8d,r9d,r10d,r11d,r12d,r13d,r14d,r15d\n"
> " .ifc \\reg, %\\rs\n"
> +" .set found, found+1\n"
> " .long \\type + (regnr << 8)\n"
> " .endif\n"
> " .set regnr, regnr+1\n"
> " .endr\n"
> +" .if (found != 1)\n"
> +" .error \"extable_type_reg: bad register argument\"\n"
> +" .endif\n"
> " .endm\n"
> );
Ooh, nice! I'd actually triggered that once. At the time it was objtool
complaining .extable size wasn't a multiple of 12. Took me a while to
figure out which one had gone missing.
> > +#define EX_FLAG_CLR_AX EX_TYPE_FLAG(1)
> > +#define EX_FLAG_CLR_DX EX_TYPE_FLAG(2)
> > +#define EX_FLAG_CLR_AX_DX EX_TYPE_FLAG(3)
>
> I'd like to buy two vowels: CL̲E̲AR
Yes, can do. The macro name was longer earlier on, but in this form we
can add the two characters.
> (I hope that Wheel of Fortune reference isn't too US-centric.)
Sadly not, TV was infested with crap like that here in .nl as well.
> > +static inline unsigned long *pt_regs_nr(struct pt_regs *regs, int nr)
> > +{
> > + /* because having pt_regs in machine order was too much to ask */
> > + switch (nr) {
> > + case 0: return ®s->ax;
> > + case 1: return ®s->cx;
> > + case 2: return ®s->dx;
> > + case 3: return ®s->bx;
> > + case 4: return ®s->sp;
> > + case 5: return ®s->bp;
> > + case 6: return ®s->si;
> > + case 7: return ®s->di;
> > +#ifdef CONFIG_X86_64
> > + case 8: return ®s->r8;
> > + case 9: return ®s->r9;
> > + case 10: return ®s->r10;
> > + case 11: return ®s->r11;
> > + case 12: return ®s->r12;
> > + case 13: return ®s->r13;
> > + case 14: return ®s->r14;
> > + case 15: return ®s->r15;
> > +#endif
> > + default: return NULL;
> > + }
> > +}
>
> Instead of all this craziness, why not just admit defeat and put them in
> pt_regs order in the 'extable_type_reg' macro?
That makes the macro different between 32bit and 64bit :/ Also, I just
found another, extant, copy of this function, so I can get rid of it and
use that one, see get_reg_offset() in insn-eval.c
> > +static bool ex_handler_imm_reg(const struct exception_table_entry *fixup,
> > + struct pt_regs *regs, int reg, int imm)
> > +{
> > + *pt_regs_nr(regs, reg) = (long)imm;
> > + return ex_handler_default(fixup, regs);
> > +}
> > +
> > +#define EX_TYPE_MASK 0x000000FF
> > +#define EX_REG_MASK 0x00000F00
> > +#define EX_FLAG_MASK 0x0000F000
> > +#define EX_IMM_MASK 0xFFFF0000
>
> To avoid mismatches these should probably be in the header file next to
> EX_TYPE_*_SHIFT?
Can do.
> > +
> > int ex_get_fixup_type(unsigned long ip)
> > {
> > const struct exception_table_entry *e = search_exception_tables(ip);
> >
> > - return e ? e->type : EX_TYPE_NONE;
> > + return e ? FIELD_GET(EX_TYPE_MASK, e->type) : EX_TYPE_NONE;
>
> Maybe the 'type' field should be renamed, to better represent its new
> use, and to try to discourage direct access. Not that I have any good
> ideas. Some not-so-good ideas: "handler", "flags", "_type".
How about the non-descript: "data" ?
next prev parent reply other threads:[~2021-11-05 7:54 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-04 16:47 [RFC][PATCH 00/22] x86: Remove anonymous out-of-line fixups Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 01/22] bitfield.h: Fix "type of reg too small for mask" test Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 02/22] x86,mmx_32: Remove .fixup usage Peter Zijlstra
2021-11-04 18:00 ` Borislav Petkov
2021-11-05 11:20 ` David Laight
2021-11-04 20:22 ` Josh Poimboeuf
2021-11-05 8:05 ` Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 03/22] x86,copy_user_64: " Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 04/22] x86,copy_mc_64: " Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 05/22] x86,entry_64: " Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 06/22] x86,entry_32: " Peter Zijlstra
2021-11-04 20:39 ` Josh Poimboeuf
2021-11-05 7:43 ` Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 07/22] x86,extable: Extend extable functionality Peter Zijlstra
2021-11-04 21:49 ` Josh Poimboeuf
2021-11-05 7:54 ` Peter Zijlstra [this message]
2021-11-05 10:16 ` Mark Rutland
2021-11-05 17:32 ` Sean Christopherson
2021-11-05 18:45 ` Peter Zijlstra
2021-11-05 19:17 ` Sean Christopherson
2021-11-05 19:32 ` Peter Zijlstra
2021-11-05 19:47 ` Sean Christopherson
2021-11-05 20:15 ` Peter Zijlstra
2021-11-05 20:26 ` Peter Zijlstra
2021-11-05 22:30 ` Sean Christopherson
2021-11-04 16:47 ` [RFC][PATCH 08/22] x86,msr: Remove .fixup usage Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 09/22] x86,futex: " Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 10/22] x86,uaccess: " Peter Zijlstra
2021-11-04 22:28 ` Josh Poimboeuf
2021-11-04 16:47 ` [RFC][PATCH 11/22] x86,xen: " Peter Zijlstra
2021-11-04 22:31 ` Josh Poimboeuf
2021-11-05 7:56 ` Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 12/22] x86,fpu: " Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 13/22] x86,segment: " Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 14/22] x86,ftrace: " Peter Zijlstra
2021-11-04 22:35 ` Josh Poimboeuf
2021-11-05 7:57 ` Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 15/22] x86,vmx: " Peter Zijlstra
2021-11-04 18:50 ` Paolo Bonzini
2021-11-05 18:17 ` Sean Christopherson
2021-11-05 18:52 ` Peter Zijlstra
2021-11-05 20:58 ` Peter Zijlstra
2021-11-05 22:29 ` Sean Christopherson
2021-11-06 7:05 ` Paolo Bonzini
2021-11-06 8:36 ` Peter Zijlstra
2021-11-07 19:13 ` Paolo Bonzini
2021-11-06 8:28 ` Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 16/22] x86,checksum_32: " Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 17/22] x86,sgx: " Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 18/22] x86,kvm: " Peter Zijlstra
2021-11-04 18:50 ` Paolo Bonzini
2021-11-05 7:58 ` Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 19/22] x86,usercopy_32: Simplify Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 20/22] x86,usercopy: Remove .fixup usage Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 21/22] x86,word-at-a-time: " Peter Zijlstra
2021-11-04 23:33 ` Josh Poimboeuf
2021-11-05 8:04 ` Peter Zijlstra
2021-11-04 16:47 ` [RFC][PATCH 22/22] x86: Remove .fixup section Peter Zijlstra
2021-11-04 23:00 ` Josh Poimboeuf
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20211105075400.GG174703@worktop.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=dvyukov@google.com \
--cc=jpoimboe@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=mbenes@suse.cz \
--cc=pbonzini@redhat.com \
--cc=seanjc@google.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).