Re: [PATCH v3 09/19] unwind: Introduce sframe user space unwinding

From: Jens Remus
Date: Thu Nov 07 2024 - 12:00:22 EST


On 28.10.2024 22:47, Josh Poimboeuf wrote:
...
diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c
...
+static int find_fde(struct sframe_section *sec, unsigned long ip,
+ struct sframe_fde *fde)
+{
+ struct sframe_fde __user *first, *last, *found = NULL;
+ u32 ip_off, func_off_low = 0, func_off_high = -1;
+
+ ip_off = ip - sec->sframe_addr;
+
+ first = (void __user *)sec->fdes_addr;
+ last = first + sec->fdes_nr;

Could it be that this needs to be:

last = first + sec->fdes_nr - 1;

+ while (first <= last) {
+ struct sframe_fde __user *mid;
+ u32 func_off;
+
+ mid = first + ((last - first) / 2);
+
+ if (get_user(func_off, (s32 __user *)mid))
+ return -EFAULT;
+
+ if (ip_off >= func_off) {
+ /* validate sort order */
+ if (func_off < func_off_low)
+ return -EINVAL;

Otherwise I run into this when the IP is within the function whose FDE is the last one in the .sframe section:

find_fde: IP=0x000000000110fbcc: ERROR: func_off < func_off_low (func_off=196608, func_off_low=4294224904)

110fbcc dump_sframe+0x2ec (/opt/binutils-sframe2/bin/objdump)

func idx [2275]: pc = 0x110f8e0, size = 3310 bytes <dump_sframe>
STARTPC CFA FP RA INFO
000000000110f8e0 sp+160 u u (1*1B)
000000000110f8e6 sp+160 c-72 c-48 (3*1B)
000000000110f8f6 sp+632 c-72 c-48 (3*1B)
000000000110fa82 sp+160 u u (1*1B)
000000000110fa88 sp+632 c-72 c-48 (3*1B)
0000000001110486 sp+160 u u (1*1B)
000000000111048c sp+632 c-72 c-48 (3*1B)
0000000001110574 sp+160 u u (1*1B)
000000000111057a sp+632 c-72 c-48 (3*1B)

+
+ func_off_low = func_off;
+
+ found = mid;
+ first = mid + 1;
+ } else {
+ /* validate sort order */
+ if (func_off > func_off_high)
+ return -EINVAL;
+
+ func_off_high = func_off;
+
+ last = mid - 1;
+ }
+ }
+
+ if (!found)
+ return -EINVAL;
+
+ if (copy_from_user(fde, found, sizeof(*fde)))
+ return -EFAULT;
+
+ /* check for gaps */
+ if (ip_off < fde->start_addr || ip_off >= fde->start_addr + fde->size)
+ return -EINVAL;
+
+ return 0;
+}

Thanks and regards,
Jens
--
Jens Remus
Linux on Z Development (D3303) and z/VSE Support
+49-7031-16-1128 Office
jremus@xxxxxxxxxx

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