From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
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: Thu, 4 Nov 2021 14:49:35 -0700 [thread overview]
Message-ID: <20211104214935.xl54xlr3snwmtyna@treble> (raw)
In-Reply-To: <20211104165524.925401847@infradead.org>
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"
);
> +#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
(I hope that Wheel of Fortune reference isn't too US-centric.)
> +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?
> +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?
> +
> 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".
--
Josh
next prev parent reply other threads:[~2021-11-04 21:49 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 [this message]
2021-11-05 7:54 ` Peter Zijlstra
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
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