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Date: Tue, 7 Aug 2012 18:52:53 -0400 From: Cyril Chemparathy <cyril@...com> To: Nicolas Pitre <nicolas.pitre@...aro.org> CC: <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>, <arnd@...db.de>, <catalin.marinas@....com>, <linux@....linux.org.uk>, <will.deacon@....com> Subject: Re: [PATCH 01/22] ARM: add mechanism for late code patching Hi Nicolas, On 8/4/2012 1:38 AM, Nicolas Pitre wrote: [...] >> extern unsigned __patch_table_begin, __patch_table_end; > > You could use "exttern void __patch_table_begin" so those symbols don't > get any type that could be misused by mistake, while you still can take > their addresses. > Looks like we'll have to stick with a non-void type here. The compiler throws a warning when we try to take the address of a void. [...] > Did you verify with some test program that your patching routines do > produce the same opcodes as the assembled equivalent for all possible > shift values? Especially for Thumb2 code which isn't as trivial to get > right as the ARM one. > We've refactored the patching code into separate functions as: static int do_patch_imm8_arm(u32 insn, u32 imm, u32 *ninsn); static int do_patch_imm8_thumb(u32 insn, u32 imm, u32 *ninsn); With this, the following test code has been used to verify the generated instruction encoding: u32 arm_check[] = { 0xe2810041, 0xe2810082, 0xe2810f41, 0xe2810f82, 0xe2810e41, 0xe2810e82, 0xe2810d41, 0xe2810d82, 0xe2810c41, 0xe2810c82, 0xe2810b41, 0xe2810b82, 0xe2810a41, 0xe2810a82, 0xe2810941, 0xe2810982, 0xe2810841, 0xe2810882, 0xe2810741, 0xe2810782, 0xe2810641, 0xe2810682, 0xe2810541, 0xe2810582, 0xe2810441, }; u32 thumb_check[] = { 0xf1010081, 0xf5017081, 0xf5017001, 0xf5016081, 0xf5016001, 0xf5015081, 0xf5015001, 0xf5014081, 0xf5014001, 0xf5013081, 0xf5013001, 0xf5012081, 0xf5012001, 0xf5011081, 0xf5011001, 0xf5010081, 0xf5010001, 0xf1017081, 0xf1017001, 0xf1016081, 0xf1016001, 0xf1015081, 0xf1015001, 0xf1014081, 0xf1014001, }; int do_test(void) { int i, ret; u32 ninsn, insn; insn = arm_check[0]; for (i = 0; i < ARRAY_SIZE(arm_check); i++) { ret = do_patch_imm8_arm(insn, 0x41 << i, &ninsn); if (ret < 0) pr_err("patch failed at shift %d\n", i); if (ninsn != arm_check[i]) pr_err("mismatch at %d, expect %x, got %x\n", i, arm_check[i], ninsn); } insn = thumb_check[0]; for (i = 0; i < ARRAY_SIZE(thumb_check); i++) { ret = do_patch_imm8_thumb(insn, 0x81 << i, &ninsn); if (ret < 0) pr_err("patch failed at shift %d\n", i); if (ninsn != thumb_check[i]) pr_err("mismatch at %d, expect %x, got %x\n", i, thumb_check[i], ninsn); } } Any ideas on improving these tests? -- Thanks - Cyril -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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