On 24/09/24 09:10, Tao Liu wrote:
Hi Aditya & Lianbo,
Thanks for your review on this ppc fix. Recently I'm working on
another high priority task, so I may not respond to your comments in
time, sorry for that.
On Tue, Sep 24, 2024 at 2:28 AM Aditya Gupta <adityag@xxxxxxxxxxxxx> wrote:
<...snip...>
How about this approach ?
I feel this might be more dependable, as the file command also uses
this, as well as fadump (PowerPC firmware-assisted dump) in the kernel.
As a sidenote, there is still some issue either in patch #1 or #3
causing all secondary CPUs (where swapper task is running) to show all
threads as '_end'
What do you think ?
Yes, I like the idea of extracting the abi version through vmlinux.
Thanks a lot for your approach and code, but I haven't tried your code
yet. I will test it when my current task finishes.
Sure, take your time :)
Thanks Tao,
Aditya Gupta
Thanks,
Tao Liu
Either way what you chose, I do realise the idea to utilise the
'std r2, STK_GOT(r1)' in such a way, was interesting and smart.
static bool
is_ppc64_elf_abi_v2(void)
{
const char *kernel_file = pc->namelist;
int fd, swap;
char eheader[BUFSIZE];
Elf64_Ehdr *elf64;
if ((fd = open(kernel_file, O_RDONLY)) < 0) {
error(INFO, "%s: %s\n", kernel_file, strerror(errno));
return FALSE;
}
if (read(fd, eheader, BUFSIZE) != BUFSIZE) {
error(INFO, "%s: %s\n", kernel_file, strerror(errno));
close(fd);
return FALSE;
}
close(fd);
if (!STRNEQ(eheader, ELFMAG) || eheader[EI_VERSION] != EV_CURRENT)
return FALSE;
elf64 = (Elf64_Ehdr *)&eheader[0];
swap = (((eheader[EI_DATA] == ELFDATA2LSB) &&
(__BYTE_ORDER == __BIG_ENDIAN)) ||
((eheader[EI_DATA] == ELFDATA2MSB) &&
(__BYTE_ORDER == __LITTLE_ENDIAN)));
/*
* The ABI version is stored in E_FLAGS in the ELF header, atleast for
* ppc64 binaries.
*
* These logic is also used by the 'file' command, which states this in
* its magic file:
*
* >18 leshort 20 PowerPC or cisco 4500,
* >18 leshort 21 64-bit PowerPC or cisco 7500,
* >>48 lelong 0 Unspecified or Power ELF V1 ABI,
* >>48 lelong 1 Power ELF V1 ABI,
* >>48 lelong 2 OpenPOWER ELF V2 ABI,
*
* The '>18' above means, data at 18 (0x12), which is basically
* 'elf64->e_machine', which will be 20 for PPC, and 21 for PPC64
*
* Similarly, '>>48' is offset 48 (0x30) in the file, which is
* basically 'elf64->e_flags', which has the ELF ABI version
*/
if (elf64->e_flags == 2) {
/* ABI v2 */
return TRUE;
} else if (elf64->e_flags == 1) {
/* ABI v1 */
return FALSE;
}
error(WARNING, "Unstable elf_abi v1/v2 detection.\n");
return FALSE;
}
Also, we can those values in the ELF header:
$ hexdump vmlinux-little-endian
0000000 457f 464c 0102 0001 0000 0000 0000 0000
0000010 0002 0015 (= 21 = E_MACHINE) 0001 0000 0000 0000 0000 c000
0000020 0040 0000 0000 0000 8bf8 0040 0000 0000
0000030 0002 (= E_FLAGS = ABI) 0000 0040 0038 0002 0040 0027 0026
0000040 0001 0000 0007 0000 0000 0001 0000 0000
Also, I see 'pc->namelist' is basically the kernel filename, is that
correct ? Can that be renamed to kernel_filename or something ?
Thanks,
Aditya Gupta
Thanks,
Aditya Gupta
+ char buf1[BUFSIZE];
+ char *pos1, *pos2;
+ int errflag = 0;
+ ulong stk_got = 0;
+ static bool ret = false;
+ static bool checked = false;
+
+ if (checked == true || !symbol_exists("tm_reclaim"))
+ return ret;
+
+ sprintf(buf1, "x/16i tm_reclaim");
+ open_tmpfile();
+ if (!gdb_pass_through(buf1, pc->tmpfile, GNU_RETURN_ON_ERROR))
+ goto out;
+ checked = true;
+ rewind(pc->tmpfile);
+ while (fgets(buf1, BUFSIZE, pc->tmpfile)) {
+ // "std r2, STK_GOT(r1)" is expected
+ if (strstr(buf1, "std") &&
+ strstr(buf1, "(r1)") &&
+ (pos1 = strstr(buf1, "r2,"))) {
+ pos1 += strlen("r2,");
+ for (pos2 = pos1; *pos2 != '\0' && *pos2 != '('; pos2++);
+ *pos2 = '\0';
+ stk_got = stol(pos1, RETURN_ON_ERROR|QUIET, &errflag);
+ break;
+ }
+ }
+
+ if (!errflag) {
+ switch (stk_got) {
+ case 24:
+ ret = true;
+ case 40:
+ goto out;
+ }
+ }
+ error(WARNING, "Unstable elf_abi v1/v2 detection.\n");
+out:
+ close_tmpfile();
+ return ret;
+}
/*
* get the SP and PC values for idle tasks.
@@ -2834,9 +2880,17 @@ get_ppc64_frame(struct bt_info *bt, ulong *getpc, ulong *getsp)
sp = ppc64_get_sp(task);
if (!INSTACK(sp, bt))
goto out;
- readmem(sp+STACK_FRAME_OVERHEAD, KVADDR, ®s,
- sizeof(struct ppc64_pt_regs),
- "PPC64 pt_regs", FAULT_ON_ERROR);
+
+ if (THIS_KERNEL_VERSION >= LINUX(6,2,0) && is_ppc64_elf_abi_v2()) {
+ readmem(sp+STACK_SWITCH_FRAME_REGS, KVADDR, ®s,
+ sizeof(struct ppc64_pt_regs),
+ "PPC64 pt_regs", FAULT_ON_ERROR);
+ } else {
+ readmem(sp+STACK_FRAME_OVERHEAD, KVADDR, ®s,
+ sizeof(struct ppc64_pt_regs),
+ "PPC64 pt_regs", FAULT_ON_ERROR);
+ }
+
ip = regs.nip;
closest = closest_symbol(ip);
if (STREQ(closest, ".__switch_to") || STREQ(closest, "__switch_to")) {
--
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